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What's the return value of the following Ruby 3 code?
str = "hello\n" str.chomp!.reverse # => "olleh" str = "hello" str.chomp!.reverse # => ???
The correct answer is
nil
It raises NoMethodError
"olleh"
"hello"
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In Ruby, the String#chomp! method is used to remove the record separator (typically a newline) from the end of a string, modifying the string in place.
If the method makes no modifications (because the string does not end with a record separator), it returns nil instead of the modified string.
This behavior can lead to unexpected issues, especially when chaining methods.
Consider the following code:
str = "hello" str.chomp!.reverse # Raises NoMethodError: undefined method `reverse' for nil:NilClass
In this example:
- The string str does not end with a newline character, so str.chomp! makes no modifications and returns nil.
- The subsequent call to reverse is attempted on nil, which raises a NoMethodError because nil does not have a reverse method.
To avoid this issue, you can use a conditional check or use the non-destructive String#chomp method, which always returns a new string and does not modify the original.
str = "hello" result = str.chomp! result = str if result.nil? result = result.reverse puts result # => "olleh"
String#chompstr = "hello" result = str.chomp.reverse puts result # => "olleh"
By using String#chomp instead of String#chomp!, you avoid the potential issue of nil being returned, ensuring that the subsequent method calls operate on a valid string object.
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