Replacing Parts of a String

Every developer needs to know how to work with strings in the language they are using. The Go libraries makes replacing parts of strings easy for a developer. I will show three solutions for replacing parts of a string in Go.

Solution 1

The simple way is to use the Replace function from the strings package. This function takes in four values:

1. s: This is the reference string.
2. old: This is the value in the string we want to change.
3. new string: This is the new string value.
4. n: This is the number of times to do the replacement. If you use -1 it will replace all string values that are equal to the old value

<a href="https://medium.com/media/43d9351ad089b4470f014a0ae8bd5466/href">https://medium.com/media/43d9351ad089b4470f014a0ae8bd5466/href</a>

This is the output:

Mary had a little Gopher Gopher duck

If we change line 13 above to:

out := strings.Replace(refString, "duck", "dog", -1)

This is the output:

Mary had a little Gopher Gopher Gopher

Solution 2

When you have more than one string value to replace you should use the NewReplacer function from the strings packages. This function returns a new Replacer from a list of old, new string pairs. This method can be use to replace multiple string a once.

<a href="https://medium.com/media/d6abfd854b89c827ad40411162c62836/href">https://medium.com/media/d6abfd854b89c827ad40411162c62836/href</a>

This is the output:

John had a little Gopher Gopher

Solution 3

The more sophisticated way of replaces substring is to use regular expression or regex. For this solution, we will use the MustCompile and ReplaceAllString from the regexp package.

1. MustCompile: Creates our regular expression. In this case, it’s a string that starts with d and is followed by any characters between a and z.
2. ReplaceAllStrings: This will replace substring that matches the regular expression the string Gopher

<a href="https://medium.com/media/e44a348cecd264aeebdd47a502bdb947/href">https://medium.com/media/e44a348cecd264aeebdd47a502bdb947/href</a>

This would output:

Mary had a little Gropher Gopher

Originally published at harrisonbrock.com.