gsub in Ruby

What is gsub in Ruby?

The gsub in Ruby is a built-in method that stands for global substitution. In Ruby, the "gsub" method is similar to the "sub" method, but with a key difference: the "sub" method only replaces the first occurrence of a pattern with a specified value, while "gsub" replaces all occurrences of the pattern with the specified value.

Syntax

The gsub in Ruby has three different overloads that you can use, depending on your needs. Here are the three overloads of gsub

Parameters

• str Parameter: This is the string in which you want to replace one or more patterns with a replacement string.
• Pattern Parameter: This is the string pattern that you want to match in the str parameter. The gsub in Ruby will look for all occurrences of this pattern in the str parameter and replace them with the replacement parameter.
• Replacement Parameter: This is the string that you want to replace the matches in str with.

Return Values

The gsub in Ruby returns a new string where all the occurrences are replaced by the specified replacement value. The original string remains unchanged.

Examples

Let's take a look at a few examples to better understand how gsub in Ruby works:

Example 1:

In this example, we are replacing the word "cricket" with "football" in the string. The new string that is returned will have "football" instead of "cricket".

Example 2:

In this example, we are using a regular expression to match all the words in the string and then replacing them with their uppercase equivalents. This is done using a block of code that is passed to gsub as the second parameter.

Example 3:

In this example, we are using gsub with a regular expression pattern and a hash to globally replace occurrences of "e" and "o" in the string "Hello" with the values 3 and *, respectively.

Best ways to use gsub Ruby Method

Let's take a look at some best practices for using Gsub in Ruby effectively in our code:

Replace Patterns with a Regular Expression

One of the most powerful features of gsub in Ruby is its ability to use regular expressions to match patterns. Regular expressions are a powerful tool for searching and replacing text in a string. They allow you to match patterns in a flexible and precise way.

Here's an example:

In this example, the regular expression pattern matches any word that starts with the letter "m" or "M" and is followed by one or more word characters (\w+). Thus the gsub method matches with "Monday" and changes it to "Sunday".

Advanced gsub with Blocks

Another powerful feature of gsub is its ability to accept a block of code as the second parameter. This allows you to generate replacement text dynamically based on the match.

Here's an example:

In this example, the gsub method matches all words and reverses them.

Replacing Multiple Terms with a Hash

You can also use a hash to replace multiple terms at once. This can be useful when you have a long list of terms that need to be replaced.

Here's an example:

In this example, we are using a hash to replace the words "Morning" and "Everyone" with "Evening" and "Folks", respectively. We are using a regular expression to match all the words in the string and then using the hash to replace each matched word with its corresponding value. If a word does not have a corresponding value in the hash, it is left unchanged.