Code smells Are a Classic. It smells because there are likely many instances where it could be edited or improved. Most of these smells are just hints of something that might be wrong. Therefore, they are not required to be fixed per se… (You should look into it, though.) Previous Code Smells You can find all the previous code smells (Part i - XXVii) here. Let's continue... Code Smell 136 - Classes With just One Subclass Being generic and foreseeing the future is good (again). TL;DR: Don't over-generalize Problems Speculative Design Complexity Over-Engineering Solutions Remove the abstract class until you get more examples Context In the past, programmers told us to design for change. Nowadays, We keep following the scientific method. Whenever we find a duplication we remove it. Not before. Not with interfaces, not with classes. Sample Code Wrong class Boss(object):
    def __init__(self, name):
        self.name = name 
        
class GoodBoss(Boss):
    def __init__(self, name):
        super().__init__(name)
        
# This is actually a very classification example
# Bosses should be immutable but can change their mood
# with constructive feedback Right class Boss(object):
    def __init__(self, name):
        self.name = name  
        
# Bosses are concrete and can change mood Detection Automatic [x] This is very easy for our linters since they can trace this error at compile time. Exceptions Some frameworks create an abstract class as a placeholder to build our models over them. Subclassifying should be never our first option. A more elegant solution would be to declare since it is less coupled. an interface Tags Over Design Relations Code Smell 114 - Empty Class Code Smell 11 - Subclassification for Code Reuse Code Smell 43 - Concrete Classes Subclassified Code Smell 92 - Isolated Subclasses Names Code Smell 135 - Interfaces With just One Realization Conclusion We need to wait for abstractions and not be creative and speculative. Credits Photo by on Unsplash Benjamin Davies Writing a class without its contract would be similar to producing an engineering component (electrical circuit, VLSI (Very Large Scale Integration) chip, bridge, engine...) without a spec. No professional engineer would even consider the idea. Bertrand Meyer Software Engineering Great Quotes Code Smell 137 - Inheritance Tree Too Deep Yet another bad code reuse symptom TL;DR: Favor composition over inheritance Problems Coupling Subclassification Reuse Bad cohesion Fragile base classes Method overriding Liskov Substitution Solutions Break clases and compose them. Context Old papers recommended using classes as a specialization for code reuse. We learnt that composition is a more efficient and extensible way to share behavior. Sample Code Wrong classdef Animalia
   
end

classdef Chordata < Animalia 

end

classdef Mammalia < Chordata 

end

classdef Perissodactyla < Mammalia 

end

classdef Equidae < Perissodactyla  

end

classdef Equus < Equidae 
//Equus behaviour
end

classdef EFerus < Equus
//EFerus behaviour
end

classdef EFCaballus < EFerus
//EFCaballus behaviour    
end Right classdef Horse       
    methods        
      // Horse behavior       
    end    
end Detection Automatic [x] Many linters report . Depth of inheritance tree (DIT) Tags Hierarchies Conclusion Look after your hierarchies and break them often. Relations Code Smell 11 - Subclassification for Code Reuse Code Smell 43 - Concrete Classes Subclassified Code Smell 58 - Yo-yo Problem Code Smell 37 - Protected Attributes Code Smell 125 - 'IS-A' Relationship Code Smell 58 - Yo-yo Problem More Info Coupling: The one and only problem Wikipedia Software entities (classes, modules, functions, etc.) should be open for extension, but closed for modification. Bertrand Meyer Software Engineering Great Quotes Code Smell 138 - Packages Dependency There's an industry trend to avoid writing code as much as possible. But this is not for free TL;DR: Write your code unless you need an existing complex solution Problems Coupling Security problems Architectural complexity Packages Corruption Solutions Import and implement trivial solutions Rely on external and mature dependencies Context Recently, There's a trend to rely on a hard to trace dependencies. This introduces coupling into our designs and architectural solutions. Sample Code Wrong $ npm install --save is-odd

// https://www.npmjs.com/package/is-odd
// This package has about 500k weekly downloads
// https://github.com/i-voted-for-trump/is-odd/blob/master/index.js

module.exports = function isOdd(value) {
  const n = Math.abs(value); 
  return (n % 2) === 1;
}; Right function isOdd(value) {
  const n = Math.abs(value); 
  return (n % 2) === 1;
};

// Just solve it inline Detection Automatic [x] We can check our external dependencies and stick to the minimum. We can also depend on a certain concrete version to avoid hijacking. Tags Security Conclusion Lazy programmers push reuse to absurd limits. We need a good balance between code duplication and crazy reuse. As always, there are rules of thumb but no rigid rules. Relations Code Smell 94 - Too Many imports More Info Poisoned Packages Packages Corruption Copyright Threats Malware in Packages Credits Photo by on olieman.eth Unsplash Thanks to Ramiro Rela for this smell Complexity kills. It sucks the life out of developers, it makes products difficult to plan, build and test, it introduces security challenges, and it causes end-user and administrator frustration. Ray Ozzie Software Engineering Great Quotes Code Smell 139 - Business Code in the User Interface Validations should be on the interface, or not? TL;DR: Always create correct objects in your back-ends. UIs are accidental. Problems Security problems Code Duplication Testability Extensibility to APIs, micro-services, etc. Anemic and objects mutable Bijection Violation Solutions Move your validations to the back-end. Context Code Duplication is a warning for premature optimization. Building a system with UI validations might evolve to an API or external component consumption. We need to validate objects on the back-end and send good validation errors to client components. Sample Code Wrong <script type="text/javascript">

  function checkForm(form)
  {
    if(form.username.value == "") {
      alert("Error: Username cannot be blank!");
      form.username.focus();
      return false;
    }
    re = /^\w+$/;
    if(!re.test(form.username.value)) {
      alert("Error: Username must contain only letters, numbers and underscores!");
      form.username.focus();
      return false;
    }

    if(form.pwd1.value != "" && form.pwd1.value == form.pwd2.value) {
      if(form.pwd1.value.length < 8) {
        alert("Error: Password must contain at least eight characters!");
        form.pwd1.focus();
        return false;
      }
      if(form.pwd1.value == form.username.value) {
        alert("Error: Password must be different from Username!");
        form.pwd1.focus();
        return false;
      }
      re = /[0-9]/;
      if(!re.test(form.pwd1.value)) {
        alert("Error: password must contain at least one number (0-9)!");
        form.pwd1.focus();
        return false;
      }
      re = /[a-z]/;
      if(!re.test(form.pwd1.value)) {
        alert("Error: password must contain at least one lowercase letter (a-z)!");
        form.pwd1.focus();
        return false;
      }
      re = /[A-Z]/;
      if(!re.test(form.pwd1.value)) {
        alert("Error: password must contain at least one uppercase letter (A-Z)!");
        form.pwd1.focus();
        return false;
      }
    } else {
      alert("Error: Please check that you've entered and confirmed your password!");
      form.pwd1.focus();
      return false;
    }

    alert("You entered a valid password: " + form.pwd1.value);
    return true;
  }

</script>

<form ... onsubmit="return checkForm(this);">
<p>Username: <input type="text" name="username"></p>
<p>Password: <input type="password" name="pwd1"></p>
<p>Confirm Password: <input type="password" name="pwd2"></p>
<p><input type="submit"></p>
</form> Right <script type="text/javascript">

  // send a post to a backend
  // backend has domain rules
  // backend has test coverage and richmodels
  // it is more difficult to inject code in a backend
  // Validations will evolve on our backend
  // Business rules and validations are shared with every consumer
  // UI / REST / Tests / Microservices ... etc. etc.
  // No duplicated code
  function checkForm(form)
  {
    const url = "https://<hostname/login";
    const data = {
    };

    const other_params = {
        headers : { "content-type" : "application/json; charset=UTF-8" },
        body : data,
        method : "POST",
        mode : "cors"
    };

    fetch(url, other_params)
        .then(function(response) {
            if (response.ok) {
                return response.json();
            } else {
                throw new Error("Could not reach the API: " + response.statusText);
            }
        }).then(function(data) {
            document.getElementById("message").innerHTML = data.encoded;
        }).catch(function(error) {
            document.getElementById("message").innerHTML = error.message;
        });
    return true;
  }

</script> Detection Semi-Automatic [x] We can detect some behavior patterns in our UI code Exceptions If you have strong evidence on severe performance bottlenecks you need to automatically duplicate your business logic on the frontend. You cannot just skip the backend part. You should not make it manually because you will forget to do it. Tags Mutability Conclusion Use . TDD You will put all your business logic behavior on your domain objects. Relations Code Smell 97 - Error Messages Without Empathy Code Smell 01 - Anemic Models Code Smell 40 - DTOs Code Smell 90 - Implementative Callback Events Code Smell 78 - Callback Hell More Info The Evil power of Mutants Credits Photo by on Unsplash Lenin Estrada I think another good principle is separating presentation or user interface (UI) from the real essence of what your app is about. By following that principle I have gotten lucky with changes time and time again. So I think that's a good principle to follow. Martin Fowler Software Engineering Great Quotes Code Smell 140 - Short Circuit Evaluation We learn short circuits in our first programming courses. We need to remember why. TL;DR: Be lazy when evaluating boolean conditions Problems Side effects Fault Bijection Performance issues Solutions Use a short circuit instead of a complete evaluation Context We learn booleans in our 101 computer courses. Boolean's truth tables are great for mathematics, but we need to be more intelligent as software engineerings. Short circuit evaluation helps us to be lazy and even build invalid full evaluations. Sample Code Wrong <?

if (isOpen(file) & size(contents(file)) > 0)
  // Full evaluation 
  // Will fail since we cannot retrieve contents 
  // from not open file Right <?

if (isOpen(file) && size(contents(file)) > 0)
  // Short circuit evaluation 
  // If file is not open it will not get the contents Detection Automatic [x] We can warn our developers when they use full evaluation. Exceptions Don't use short-circuit as an IF alternative. if the operands have side effects, this is another code smell. Tags Boolean Conclusion Most programming languages support short-circuits. Many of them have it as the only option. We need to favor these kinds of expressions. Relations Code Smell 101 - Comparison Against Booleans Code Smell 69 - Big Bang (JavaScript Ridiculous Castings) More Info Wikipedia Writing a class without its contract would be similar to producing an engineering component (electrical circuit, VLSI (Very Large Scale Integration) chip, bridge, engine...) without a spec. No professional engineer would even consider the idea. Bertrand Meyer Software Engineering Great Quotes Next article, 5 code smells more

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