meetergo

Topographical Notes

In the cluttered cyber world of copycats & vaporware, Solana { } stands out from the crowd with its unique design & value proposition. SOL (sometimes jokingly called solami by the degen chads on ) CT *Disclaimer* → I hold in my portfolio & believe in the future of the project. $SOL → This is not an endorsement to buy the coin or use the network. (Do you) → Solana is home to a prolific NFT community… however, there will be of NFTs in this post because, at this time, there are too many failures, frauds, rugs & scams. *one exception being Sol domain names*. no mention → This is strictly a general overview of the network. Not about degens or monke pictures… ok, just a tiny bit about degening. 📜 A Bit of Background Conceptualized in 2017 by ex-Qualcomm engineer & birthed in march of 2020, Solana is a turning complete, smart contract platform & distributed ledger network that was created with the intention of displacing the legacy exchange infrastructure(not killing Ethereum). Anatoliy Yakoveno The Solana network was & continues to be one of the most exciting innovations in the space due to its dedication to the technological elements of its design. heavy 👨‍💻 The Technical Specs 👨‍💻 Monolithic Architecture ➡ Monolithic software architecture in blockchain means that all major operational activity; transaction execution, data storage/availability, and consensus, are condensed into a single endpoint; the chain itself. This design brings its own set of tradeoffs including better prospective value propositions for the native asset due to strong utility ties between the token<->network (NFA) while hindering its potential to be flexible. {Great resource on blockchain software architecture here} Example of another crypto with Monothlic architecture: Bitcoin (BTC). POH (Proof-Of-History) ➡ Proof-Of-History is a novel tweak to the POS consensus model through the implementation of as a module. Technically, Proof of History happens before state consensus is reached by allowing block producers the ability to submit blocks & organize/confirm them later. This is made possible by a combination of two things: time & 1) the application of pBFT + VDF (verifiable delay functions) the ( ). That helps in eliminating the issue of scalability and transaction ordering. Clustering of consensus nodes rather than 1 node doing all the work, on Solana, there are clusters of 25 nodes that are batching tx’s for consensus at any given time Asynchronicity in block production & contract execution ➡ Basically, the ability to operate at max capacity without bloating/interrupting the network. (outages mentioned in the next section) Partially made possible through node clustering & partially made possible through a parallel processing technique called . Sealeveling The technical aspect of this are far beyond the scope of this article, but if you want to dive deeper on it, make sure to check out this post Written in RUST programming language ➡ While not easy to learn for beginner developers, RUST is considered to be among the strongest of programming languages. At a very basic level, RUST is a low-level language that talks directly to hardware with an intense focus on memory allocation. Here is a great piece to understand the benefits of RUST as a language. * Multi-Client Architecture ( ) ➡ in development Within the context of blockchain, a is the software that must be utilized in order to connect a piece of hardware to the network. client A delicate nuance in distributed system design that is rarely (if ever) brought to the public’s consciousness, is that software clients are an important touchpoint for the security & decentralization of a network. If a network only has 1 software client, and if for any reason that client has a bug, then the whole network is at risk. The more clients, the more resilient the network becomes. Extremely Fast ➡ The block time is 400 milliseconds; that is approximately 30–32.5x faster than Ethereum(ETH) & 1,500x faster than Bitcoin (BTC). Huge & growing developer ecosystem ➡ Over 2,000 monthly active developers puts Solana as the 2nd most active network by developer activity; ahead of Polkadot & only behind Ethereum. High Throughput ➡ The network averages ~5,000 TPS on a day-to-day basis & has the capacity to scale, in theory, indefinitely. The network is only constrained by the amount & type of hardware used by the nodes. As hardware improves, the network becomes more efficient; as more nodes join, the network becomes more efficient. So then LFGrow. ⚠ 💨⚠ 💨 Headwinds ➡ Is a VC chain. Supported heavily by deep-pocketed venture capital firms. This is not necessarily a bad thing, but it does reduce the network's credibility in terms of decentralization. Was endorsed by (SBF) & FTX; ➡ As basically everybody in the world knows, Sam-Bankman Fried was the single biggest supporter of the Solana network. Actually recorded saying “ ” as well as injecting hundreds of millions of dollars into the project, the once heroic supporter has now become the sh*tstain across the windshield of Solana’s life. Sell me all of your Solana & then Fuck off Suffers from Outages ➡ The single biggest hurdle that keeps on messing with the project. This is not a small issue; if outages happen while people have money on the network, real-life problems occur. As of this writing, the network has faced roughly 10 full outages & countless partial outages. If you want to explore all of them, here is a great uptime resource. Community is… interesting. ➡ I love SOL. I love the developers. I love the project. I Even love Solana ! But I cannot for the life of me figure out how it keeps attracting low-IQ people to its user base. At first, I thought it was just wrought with bots… but then I found out… CT Dear reader, I SWEAR to you, I personally know real SOL users that pronounce SolanA as SolanO. I asked them why… they don't know… 🤦‍♂️ I digress. 🧰Ecosystem Resources: Since the turbulence of the recent market activity, many tools in the Solana ecosystem are sunsetting (r.i.p. Serum) while others are just dying off due to a lack of interest. Nevertheless, there still remain a handful of applications that have only strengthened their positions over this time. Below, I have tried my best to organize as many “valid” tools as possible: Wallets Phantom - https://phantom.app/ Solflare - https://solflare.com/ DEXes Raydium - https://raydium.io/ Orca - https://www.orca.so/ Saber - https://app.saber.so/ Lifinity - https://lifinity.io/ Atrix - https://atrix.finance/ Soldex - https://soldex.ai/ Saros - https://saros.finance/ Aldrin - https://aldrin.com/ DexLab - https://www.dexlab.space/ Crema - https://www.crema.finance/ Lending/Borrowing & Stablecoin Minting Larix - https://projectlarix.com/ Solend - https://solend.fi/ Apricot - https://apricot.one/ Port - https://port.finance/ Jet - https://www.jetprotocol.io/ PsyFI - https://www.psyfi.io/ Hubble - https://hubbleprotocol.io/ Ratio - https://ratio.finance/ Parrot - https://parrot.fi/mint/ Meteroa - https://www.meteora.ag/ Liquid Staking Marinade - https://marinade.finance/ Socean - https://www.socean.fi/en/ Yield Aggregators Tulip - https://tulip.garden/#home Cropper - https://cropper.finance/ Katana - https://katana.so/ Kamino - https://app.kamino.finance/ Sunny - https://app.sunny.ag/ Francium - https://francium.io/ Explorers & Analtyics Solana Explorer - https://explorer.solana.com/ Solana FM - https://solana.fm/ SolScan - https://solscan.io/ Solana Beach - https://solanabeach.io/ ChainCrunch - https://chaincrunch.cc/ Synthetic Assets Synthetify - https://synthetify.io/ Dashboard & Portfolio Sonar Watch - https://sonar.watch/ Sols Watch - https://sols.watch/portfolio Step Finance - https://www.step.finance/ Ape Bored - https://apeboard.finance/dashboard Domain Names Bonfida — https://naming.bonfida.org/ MISC. → Fantastic report by Messari on the S . tate of Solana in Q4 2022 → Great Interview with the Founder on the Future of Solana beyond 2023 I will end this all with a timeless quote ; (←POH pun intended) “Innovation distinguishes between a leader and a follower.” — Steve Jobs May your bags always be full & overflowing 🥂 Also published here

Everything You Need to Know About Solana: An Essential Guide

This job hunting guide covers resumes, job application process, coding interview prep, system design interview prep, mock interview practices, behavioral interview prep, computer science fundamentals, and negotiation tips. 📝 Resume Tips Step 1: Write down your career stories in a resume You should have a of your own, basically collecting your achievements in day to day work, the challenges you’ve faced and how you solved it, it does not take much time to keep a record of these achievements, but they are super helpful when you need to revamp your resume, or write promo docs. brag list Step 2: Vet your resume Once you finish writing your resume, it is essential to have someone else to vet your resume, you can ask your friends to help with proofreading, run it through to correct grammar errors, or if your resume has never been vetted before you can find dedicated service on to review and edit your resume. Grammarly Fiverr Step 3: Take it further to build your personal brand online If you have projects you are proud of and can demonstrate your skill sets you can showcase it with one page websites. You can use to create simple, free, fully responsive one-page sites for your projects/products. Carrd If you want to take it further to establish a personal brand online as a developer, you should get a domain via registrars such as , they usually have very affordable domains. Namecheap 🎯 Apply For Jobs and Manage Your Applications Where to apply for jobs There are some popular job postings aggregator sites: : I would say LinkedIn has most of the job postings for tech, and they often give you one month free premium trial, you can use that to see more analytics about an opportunity LinkedIn and : Still being used by many companies Indeed Glassdoor : more towards startup jobs AngelList : more towards startup jobs Hired Don’t forget referrals The job posting aggregator sites are great, but if you can get someone to refer you to a position, it usually has a better response rate. Trying to reach out to your network for potential referrals is always a good thing to do. How to manage multiple applications If you are applying for multiple positions, you probably want to manage all these job applications with a tool or system to track progress and keep notes: : a great tool to manage your job search, the free tier should be sufficient for individual usage Huntr : a powerful tool to write and collaborate, for example, you can use it to summarize knowledge for coding interview, write down behavior stories and ask your friends to provide feedback. You can also find beautiful to get started faster. Notion notion templates : What’s powerful about Todoist as todo app is its natural language todo creation and advanced filter views to track todo tasks Todoist 👩‍💻 Prepare For Coding Interview If you are new to data structure and algorithm or you want to brush up on it: Udacity Course: Intro to Data Structures and Algorithms Coursera Course: , Algorithm Part I Algorithm Part 2 (it’s a big book, but to ramp up on data structure and algorithm, you probably want to read below sections/chapters first) Cracking the Coding Interview VI: Big O VII: Technical Questions IX: Interview Questions(Chapter 1-5, 7-10 since they cover common coding interview questions) There are many other classic books or courses on data structure and algorithms, but to ace coding interviews, we should focus on practicing to solve common coding interview questions, there is no shortcut, practice makes perfect. Having said that, as of right now there are already more than 2500 practice problems on , we also need to be smart about preparing for coding interviews. Leetcode A common and effective strategy I’ve seen many people used and worked(including myself) is: Step 1: Learn the fundamentals After learning about the fundamentals of a data structure or an algorithm, try to solve some corresponding classic problems. You can check this book (or in Elements of Programming Interviews in Python ) Java is a great tool if you want to spend less time but get the best coverage of frequently asked coding interview questions Grind 75 questions Leetcode has a couple of study plans such as , (some problems may require premium to unlock) Binary Search Study Plan Graph Theory Study Plan Neetcode has for studying data structure and algorithm roadmap Step 2: Recognize patterns Once you are familiar with these topics, now it’s time to see if you are able to recognize which data structure or algorithm to use when you encounter a new problem During this phase, you can try to follow to solve a problem this approach Some community resources like is also helpful to learn about patterns this leetcode patterns Step 3: Mock Interviews Once you are confident you can solve most new problems, the next step is to practice mock interviews Note that Leetcode has a feature, you can try this feature to see if you can solve a problem within limited time, it mimics the online assessment in interview pipelines Mock Assessment A more challenging yet common way to evaluate candidates is to have an interviewer work with you to solve a problem, it usually requires the candidates to be able to clarify requirements, communicate his or her thought process and solve the problem within a limited time. Other words, you also need to practice this scenario. is a free platform where you can pair with random peers to mock this type of interview Pramp also provides mock interview with FAANG engineers, although it’s pricey, personally I think if you practice enough on Pramp and Leetcode it should be sufficient, but up to you if you want to invest a bit more in getting a FAANG engineer to mock coding interview with you interviewing.io Coding interview Popular Youtube Channels Tushar Roy - Coding Made Simple Back To Back SWE Abdul Bari Byte by Byte WilliamFiset Other useful resources Big O cheatsheet Design Patterns Refactoring A Philosophy of Software Design 🧑‍🎨 Prepare For System Design Interview If you are targeting senior and above level, system design is probably where you would want to spend more time on, since this is usually where the employer see if you are qualified for the level you are applying for, if your day-to-day work doesn't include a lot of hands-on system design, you may want to plan time ahead to prepare this type of interview, even if you have the work experience, designing in an interview setting is different than designing in day-to-day work, so you have to prepare for it. Step 1: Learn Basics The System Design Primer : highly recommended by many people, it is very helpful especially if you are not familiar with distributed or data intensive systems, note that this book is not intended for interview per se, but it will help you close some knowledge gaps. Designing Data-Intensive Applications : The book is geared toward system design interview, it includes a recommended flow of solving a system design interview question, and uses several common questions to explain this flow. System Design Interview – An insider's guide : The second volume contains much more details than the first book and covers more domains. You can even just use it to learn what aspects to consider when designing for a particular domain. System Design Interview – An Insider's Guide: Volume 2 PEDALS method Google Site Reliability Engineering book System Design Popular Youtube channels : It has many great recordings from those who worked on large scale systems InfoQ : It has recordings from tech conferences maintained by engineering community at Meta System @Scale : It will share some mock interview recordings where you can observe and hear the feedback from the mock interviewer. interviewing.io : It goes over some common system design problem in depth. System Design Interview : This community also has regular mock interview sessions SDE Skills : It is the owner of the Pramp mock interview platform, sometime they share mock interview recordings Exponent : He shared videos on common backend system problems, it is not geared toward interviews, but is helpful in terms of learning backend in general Hussein Nasser Courses If you prefer to spend your time efficiently on high quality and well instructed videos, is created by the same person who owns this Youtube channel(if you ever searched system design videos on YouTube, mostly likely you’ve seen into this channel before) System Design for Interviews and Beyond System Design Interview also has some system design courses(note its courses is mainly in text) Educative Scalability & System Design for Developers Grokking Modern System Design Interview for Engineers & Managers Step 2: Mock Interview I can’t stress enough about the importance of mock interviews, you learn from the feedback, adjust or learn, then rinse and repeat, it applies to system design interviews as well. You can also set up random peer mock system design interviews on . However for system design interviews, the feedback is often valuable when your peer is already an experienced engineer, this is not always guaranteed since the platform pairs peers randomly. Pramp I would say try to find people who are more experienced in your network see if they can help with mock interview, but if you think this is your bottleneck, perhaps check to find some experienced engineers to mock and provide detailed feedback with you could be a good investment(they also release some video recording on ) interviewing.io YouTube Other Resources (From Microsoft Azure) Cloud Design Patterns Latency Numbers Book(although it is slightly more abstract, not just for interview) Fundamentals of Software Architecture Curated list of engineering blogs 🙇Prepare For Behavior Rounds To nail the behavior round, it highly depends on what role or level you are interviewing at, but a few things that are generally helpful is to 1)keep note of your achievements and challenges you solved at work 2)use format such as to tell your story. STAR There are some resources showing you common mistakes you want to avoid and tips during behavior interview: Courses Grokking the Behavioral Interview Rock the Behavioral Interview Youtube Channels DanCroitor Candidate Planet Self Made Millennial Jeff H Sipe Other Resources Cracking the soft skills (usually towards the end of the interview you will have a few minutes to ask questions, it is also a great opportunity to learn about your potential employers, remember the interview is a two way street) The Reverse Interview 💻 Computer Science Fundamentals Depending on the company and position you are interviewing for, you may need to refresh on computer science. With the time constraints of getting ready for an interview, I recommend finding the knowledge gap you need to close and close it, instead of going through the material sequentially(but if you have the time to go through the books or courses, it’s always good to learn). Open source courses Udacity: Networking for developers Udacity: Intro to OS Coursera: Networking by Google Udacity: Computer Networking MIT: Computer System Engineering MIT: Distributed Systems CMU: Database Systems Books Computer Systems: A Programmer’s Perspective Code: The Hidden Language of Computer Hardware and Software Operating Systems: Three Easy Pieces 🤝Negotiate Offers To negotiate offers you need to know the market, you may also get this question at the beginning of the interview pipeline as well, whether you want to disclose is up for you, but it’s always good to know the market trend, here are some resources to help:** ** : Youtube channel talks about negotiation Candidate Planet : It has the most comprehensive data points for tech jobs levels.fyi : mostly 🇨🇦 tech job data points meterwork : not just for tech jobs payscale : not just for tech jobs, not too many data points there but you can check the review and ratings glassdoor : it has ratings and reviews for a company, and some time you can see people sharing compensation anonymously Teamblind I’ve compiled and curated a list of job hunting resources for software developers, it covers resources for writing resumes, applying and managing job applications, efficient ways to prepare for coding interviews, resources to learn system design, you can download the full free PDF . here Note: This article is based on my personal experience. If you have more suggestions please leave them in the comments below.. I’m always open to meet new people so feel free to contact me on . Twitter Also published . here Thanks for reading! If you enjoyed this story, show your support by sharing with your friends! Additional references Practical guide to writing FAANG-ready software engineer resume to learn about what a good tech resume looks like and why The Tech Resume Inside Out ’s section Cracking the Coding Interview Introduction-Before the Interview Image credit, prompt of “a robot prepares to make software inside a computer.” HackerNoon AI

The Ultimate Guide to Software Development Job Interview Prep 

Ultimate Guide to Software Development Job Interview Prep 

The shift to a more digital work culture that has been emphasized since the start of the pandemic, made video conferencing an integral part of the daily routine for a lot of people. By now there are very few who are not familiar with Zoom, Google Meet, Microsoft Teams, and the countless other video meeting tools available. The majority of these ‘online meeters’ know how to easily share screens, set up a web camera, and how to look nice on a video stream. What about adding a security camera to a video conferencing room? In our increasingly connected world, we are accustomed to staying connected and maintaining communication with colleagues despite physical distance. There is a range of use cases that would benefit greatly from adding security (or IP) cameras to virtual rooms, for instance, security personnel, first responders, city traffic controllers, police, etc. Why security cameras? Why not just add a normal web camera instead? Security cameras (aka IP-cameras) usually transmit video via RTSP. Even though this is a widely used protocol, bringing this kind of video stream into an active video meeting can be difficult or even impossible. Another streaming protocol widely used is called RTMP. , together with , developed a unique solution to bring RTSP and RTMP streams from security cameras to online meetings by transcoding them to WebRTC and adding it to an eyeson video conferencing room. Trembit eyeson Adding camera streams on the fly to video meetings can unlock a variety of use cases Both RTMP and RTSP are streaming protocols used for low latency video streaming. RTMP is widely used by broadcasters, whereas RTSP is used for streaming from IP cameras. Streaming IP cameras into video meetings where all participants see the same feed is essential to achieve transparent processes and trustworthy assessment. For use cases of this type, integrating security camera streams into the video meetings brings significant added value compared to downloading the footage and uploading it afterward. In the case of command & control operations, streaming the camera footage directly onto the meeting mitigates the lag issue that impacts the user's attention, information dissemination, and engagement. The difference between live streaming and sharing downloaded video via screen sharing makes a significant difference to the mission’s success. Video streams can be crucial for police missions, drone operations or surveillance needs enabling participants to join from anywhere securely and share circumstances live: a situation room with participants all over the world can be set quickly up by providing a secret link to it. No setup, no installation, and maximum security. Besides, prerecorded video footage, maps, and additional information can be shown without the need for screen sharing and without lags. Review and learn - yet another advantage In the use cases described above, the possibility of reviewing and learning from what happened is essential. Recording the meeting, and therefore recording what happens, with all participants seeing the same is a big advantage for teams to evolve and train.

Should Security Cameras be Used in Online Meetings?

20 Best Social Media Management Tools for Small Businesses

We are gonna’ look into cloning Django model instances, applicability of Iterator and Visitor patterns, and a little bit into Django models metadata. If you want to look into final code - visit github repository - https://github.com/regqueryvalueex/django-relations-iterator So, what’s the issue? Lately, working with some Django code I faced a need to implement proper cloning feature. A brief search on the internet gave me some packages for cloning, but I wasn’t satisfied with those. So it’s time to write some code by myself. Simplest clone in Django looks like this # models.py
class Meeting(models.Model):
    title = models.CharField(max_length=200)

# clone

instance = Meeting.objects.last()
instance.pk = None
instance.save() This will create new row in database with the same data as original instance have. However if you want also clone some related objects, you may have to manually go over all related objects and clone them as well. Also don’t forget to set correct foreign key value, so you will have correct hierarchy # models.py
class Meeting(models.Model):
    title = models.CharField(max_length=200)


class Participation(models.Model):
    meeting = models.ForeignKey('Meeting', on_delete=models.CASCADE, related_name='participations')

# clone

def clone(instance):
    instance.pk = None
    instance.save()
    return instance

instance = Meeting.objects.last()
related_objects = instance.participations.all()
cloned_instance = clone(instance)

for related_object in related_objects:
    related_object.meeting = cloned_instance
    clone(related_object) Well, it works, kinda. Lets summarize issues with this requires to manually hardcode all cloning process for all relations will copy all the data from original instances, event if you don’t need this we don’t have any convenient or clear way to controll process for different instances adding new models to hierarchy will require us to add new code to this But what exactly do we want from this feature? must provide automatic way to walk over hierarchy must provide possibility to control clone process for different instances must provide control over relation that will be cloned must be reusable for different models and hierarchies Lets see what we can do… Step 1. Setup test models from django.conf import settings
from django.db import models


class Meeting(models.Model):
    title = models.CharField(max_length=200)
    time = models.DateTimeField(null=True, blank=True)
    participants = models.ManyToManyField(
        settings.AUTH_USER_MODEL,
        through='Participation',
        blank=True
    )


class Participation(models.Model):
    meeting = models.ForeignKey(
        'Meeting',
        on_delete=models.CASCADE,
        related_name='participations'
    )
    user = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.CASCADE,
        related_name='participations'
    )


class Invitation(models.Model):
    status = models.CharField(max_length=20, default='sent)
    participation = models.ForeignKey(
        'Participation',
        on_delete=models.CASCADE,
        related_name='invitations'
    )


class Comment(models.Model):
    meeting = models.ForeignKey(
        'Meeting',
        on_delete=models.CASCADE,
        related_name='comments'
    )
    user = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
    description = models.TextField(max_length=3000) Step 2. Determine and configure model relations Django models have an interface for model metadata, we can read info about relations there print(Meeting._meta.related_objects)
# (<ManyToOneRel: meetings.participation>, <ManyToOneRel: meetings.comment>)
print(Participation._meta.related_objects)
# (<ManyToOneRel: meetings.invitation>,)
print([relation.get_accessor_name() for relation in Meeting._meta.related_objects])
# ['participations', 'comments'] Method simply returns a name, that can be used to access related objects, also we can retrieve corresponding relation field with that field get_accessor_name print(Meeting._meta.get_field('participations'))
<ManyToOneRel: meetings.participation>
print(Meeting._meta.get_field('comments'))
<ManyToOneRel: meetings.comment> Good, so considering this we can create simple configuration, using relation names. Lets say, we want to include , , and , but must be excluded. Meeting Participation Invitation Comment # Simple config
structure = {
    'participations': {
        'invitations': {}  # No relations - empty dict
    }                      #  `comments` isn't here
} Step 3. Collecting instances accordingly to the config # Let's create instances first
tom = User.objects.create(username='Tom')
jerry = User.objects.create(username='Jerry')
meeting = Meeting.objects.create(title='dinner')
tom_participation = Participation.objects.create(user_id=tom.id, meeting_id=meeting.id)
jerry_participation = Participation.objects.create(user_id=jerry.id, meeting_id=meeting.id)
Invitation.objects.create(user_id=jerry.id, meeting_id=meeting.id)
Comment.objects.create(user_id=jerry.id, meeting_id=meeting.id) Now, when we have some data, we can work with this. So, considering the nature of the data, we can use recursion to iterate over our config and put data, obtained from db, into dict. We can tell, that result must look like a tree, so lets create a couple of classes and make some basic tree import typing

from django.db.models import Model, ManyToManyRel, ManyToOneRel, OneToOneRel

Relation = typing.Union[ManyToManyRel, ManyToOneRel, OneToOneRel]
RelationTree = typing.Dict['TreeNode', typing.Dict[Relation, 'RelationTree']]
RelationTreeConfig = typing.Dict[str, 'RelationTreeConfig']


class TreeNode:
    def __init__(
        self,
        *,
        instance: Model,
        parent: typing.Optional['TreeNode'] = None,
        relation: typing.Optional[Relation] = None
    ):
        self.instance = instance
        self.parent = parent
        self.relation = relation

    @property
    def model_class(self):
        return type(self.instance)

    def __hash__(self):
        return hash(f'{str(self.model_class)}-{self.instance.id}')

    def __repr__(self):
        return f'<{type(self).__name__} for {repr(self.instance).strip("<>")}>'


class ConfigurableRelationTree:
    def __init__(self, *, root: Model, structure: RelationTreeConfig):
        self.root: Model = root
        self.structure: RelationTreeConfig = structure
        self.tree: RelationTree = self.collect()

    def collect(
        self,
        *,
        root_node: typing.Optional[TreeNode] = None,
        structure: typing.Optional[RelationTreeConfig] = None
    ) -> RelationTree:
        if not root_node:
            root_node = self.get_node(instance=self.root)

        root = root_node.instance
        structure = structure if structure is not None else self.structure
        subtree = {}
        tree = {root_node: subtree}

        for sub_relation_name, substructure in structure.items():
            sub_relation = root._meta.get_field(sub_relation_name)
            related_instances = self._get_related_instances(instance=root, relation=sub_relation)
            subtree[sub_relation] = {}
            for related_instance in related_instances:
                node = self.get_node(instance=related_instance, relation=sub_relation, parent=root_node)
                subtree[sub_relation].update(
                    self.collect(root_node=node, structure=substructure)
                )

        return tree

    def _get_related_instances(
        self,
        *,
        instance: Model,
        relation: Relation
    ) -> typing.List[Model]:
        accessor_name = relation.get_accessor_name()
        if relation.one_to_one:
            instance = getattr(instance, accessor_name, None)
            related_instances = [instance] if instance is not None else []
        else:
            related_instances = list(getattr(instance, accessor_name).all())
        return related_instances

    def get_node(
        self,
        *,
        instance: Model,
        parent: typing.Optional[TreeNode] = None,
        relation: typing.Optional[Relation] = None
    ) -> TreeNode:
        return TreeNode(
            instance=instance,
            parent=parent,
            relation=relation,
        ) Lets see what do we have: from pprint import pprint
tree = ConfigurableModelTree(root=meeting, structure=structure)
pprint(tree._tree)

# {
#     <TreeNode for Meeting: Meeting object (1)>: {
#         <ManyToOneRel: meetings.participation>: {
#             <TreeNode for Participation: Participation object (1)>: {   
#                 <ManyToOneRel: meetings.invitation>: {
#                     <TreeNode for Invitation: Invitation object (1)>: {}
#                 }
#             },
#             <TreeNode for Participation: Participation object (2)>: {
#                 <ManyToOneRel: meetings.invitation>: {}
#             }
#         }
#     }
# } Good, seems like we have correct structure. So how we gonna use it? Here, where’s patterns come to our help Step 4. Get familiar with Iterator and Visitor patterns Fortunately, programmers around the world have been working with data for many years and have many good solutions to solve almost any question. Our question is - How to create reusable solution to iterate over our tree structure? Answer is - Iterator pattern Iterator is a behavioral design pattern that lets you traverse elements of a collection without exposing its underlying representation (list, stack, tree, etc.). Our other question: How to create a reusable solution to operate with tree nodes? And the answer for that - Visitor pattern Visitor is a behavioral design pattern that lets you separate algorithms from the objects on which they operate. And what event better - these patterns work great together. Step 5. Implement simple Iterator and Visitor Python have built-in , so we can simply just use that. Simple implementation of method, that returns generator will be enough. iterator protocol __iter__ import typing


from abc import ABC, abstractmethod


# I will use abstract class to define interface 
class AbstractRelationTreeIterator(ABC):
    @abstractmethod
    def get_iterator(self, tree: typing.Optional[RelationTree] = None):
        pass

    def __iter__(self):
        return self.get_iterator()


class RelationTreeIterator(AbstractRelationTreeIterator):
    def __init__(self, tree: ConfigurableRelationTree):
        self.tree = tree

    def get_iterator(self, tree: typing.Optional[RelationTree] = None):
        tree = tree if tree is not None else self.tree.tree
        for node, subtree in tree.items():
            yield node
            for relation, subnodes in subtree.items():
                # since we iterate over tree, we need recursion here as well
                yield from self.get_iterator(subnodes) For visitor, it’s even simpler: class AbstractVisitor(ABC):
    @abstractmethod
    def visit(self, node: TreeNode):
        pass


class CloneVisitor(AbstractVisitor):
    def visit(self, node: TreeNode):
        node.instance.pk = None
        if node.parent is not None:
            parent_joining_column, instance_joining_column = node.relation.get_joining_columns()[0]
            setattr(
                node.instance,
                instance_joining_column,
                getattr(node.parent.instance, parent_joining_column)
            )
        node.instance.save() Method will return columns, that involved in relation between models. For and it will return , and that exactly what we need, since is a correct foreign key assignment. get_joining_columns Meeting Participation (('id', 'meeting_id'),) participation.meeting_id = meeting.id Step 6. See, how it works So, how do you use visitor and iterator together. Well you just iterate over your data structure using iterator and use visitor for every item: tree = ConfigurableRelationTree(root=meeting, structure=structure)
visitor = CloneVisitor()
for node in RelationTreeIterator(tree):
    visitor.visit(node)

pprint(tree.tree)
# {
#     <TreeNode for Meeting: Meeting object (3)>: {
#         <ManyToOneRel: meetings.participation>: {
#             <TreeNode for Participation: Participation object (5)>: {
#                 <ManyToOneRel: meetings.invitation>: {
#                     <TreeNode for Invitation: Invitation object (3)>: {}
#                 }
#             },
#             <TreeNode for Participation: Participation object (6)>: {
#                 <ManyToOneRel: meetings.invitation>: {}
#             }
#         }
#     }
# } As you can see, we have different ids here, so new instances was created in database for this hierarchy. Step 7. Make cloning process configurable Its very common, that you need to have control over cloned data. For instance, in our case, we probably don’t want to have the same in cloned instance. And maybe we want to add some extra text to meeting title, like . time f'{original_title}-COPY' Classical Visitor patters suggests us to implement method in our class , that will accept a Visitor instance and will call a proper implementation. That is a good way to handle different requirements for different classes, however I want to keep and untouched, and rely on other tools. Fairly often because different languages have some powerful tools, they allow to simplify some classical patterns. For example or in some cases event replace it. TreeNode ConfigurableRelationTree TreeNode First class functions can simplify Strategy pattern For our case, we can use functools.singledispatch from functools import singledispatch


@singledispatch
def customize(instance):
    pass


@customize.register
def _(instance: Meeting):
    instance.title = f'{instance.title}-COPY'
    instance.time = None


# Changed ClonedVisitor
class CloneVisitor(AbstractVisitor):
    def visit(self, node: TreeNode):
        node.instance.pk = None
        if node.parent is not None:
            parent_joining_column, instance_joining_column = node.relation.get_joining_columns()[0]
            setattr(
                node.instance,
                instance_joining_column,
                getattr(node.parent.instance, parent_joining_column)
            )
        # added customize call
        customize(node.instance)
        node.instance.save() Let’s see now how it works structure = {
    'participations': {
        'invitations': {}
    }
}
meeting = Meeting.objects.get(title='dinner')

tree = ConfigurableRelationTree(root=meeting, structure=structure)
visitor = CloneVisitor()
for node in RelationTreeIterator(tree):
    visitor.visit(node)

print(meeting.title)
# 'dinner-COPY'
print(meeting.time)
# None Note, that our structure is mutated and we actually overwrite original tree with cloned tree. That’s important, because if you want to use original instances, you need to initialize them again after clone. Conclusion Now we have a reusable approach to clone instance hierarchies in Django. However it’s not limited by only clone feature. We actually can use it for other needs and all we need to do most of the time is just create new Visitor implementation, and, maybe, new Iterator implementation. Lets create a quick example, that will print path to our nodes: class PathPrintVisitor(AbstractVisitor):
    def visit(self, node: TreeNode):
        print(list(reversed(self.get_path(node))))
  
    def get_path(self, node: TreeNode):
        path = [node]
        if node.parent:
            path.extend(self.get_path(node.parent))
        return path

visitor = PathPrintVisitor()
for node in RelationTreeIterator(tree):
    visitor.visit(node)


# [<TreeNode for Meeting: Meeting object (5)>]
# [<TreeNode for Meeting: Meeting object (5)>, <TreeNode for Participation: Participation object (9)>]
# [<TreeNode for Meeting: Meeting object (5)>, <TreeNode for Participation: Participation object (9)>, <TreeNode for Invitation: Invitation object (5)>]
# [<TreeNode for Meeting: Meeting object (5)>, <TreeNode for Participation: Participation object (10)>] You may visit my github repo for this implementation and look into the code if you want to - https://github.com/regqueryvalueex/django-relations-iterator

MEETERGO

meetergo.com

-- employees

Since n.d.

COMPANY RANKING

MEETERGO

EVERGREEN INDEX #237

Representing this company? Click here to claim and customize this page!

meetergo WIKI

Apply to get your Tech Company News Page live on HackerNoon.com today!

MEETERGO

meetergo.com

-- employees

Since n.d.

COMPANY RANKING

MEETERGO

EVERGREEN INDEX #237

RELATED COMPANIESRANK

STORIES ABOUT MEETERGO

Representing this company? Click here to claim and customize this page!

meetergo WIKI

Apply to get your Tech Company News Page live on HackerNoon.com today!