How to check whether a string contains a substring in Ruby

If case is irrelevant, then a case-insensitive regular expression is a good solution:

'aBcDe' =~ /bcd/i  # evaluates as true

This will also work for multi-line strings.

See Ruby's Regexp class for more information.

You can also do this...

my_string = "Hello world"

if my_string["Hello"]
  puts 'It has "Hello"'
else
  puts 'No "Hello" found'
end

# => 'It has "Hello"'

This example uses Ruby's String #[] method.

You can use the include? method:

my_string = "abcdefg"
if my_string.include? "cde"
   puts "String includes 'cde'"
end

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