Change all array elements which include a specific string

Since neither answer so far instructs you on how to update the string in the array to the new value, here are some options: # Find every string matching a criteria and change them array.select{ |s| s.include? "good" }.each{ |s| s.replace( "bad" ) } # Find every string matching a pattern and change them array.grep.replace( "bad" ).each{ |s| s.replace( "bad" ) } # Find the first string matching a criteria and change it array.find{ |s| s =~ /good/ }.replace( "bad" ) However, all of the above will change every instance of a string. For example: jon = Person.new "Johnny B. Goode" array = [ jon.name, "cat" ] array.find{ |s| s =~ /good/i }.replace( "bad" ) p array #=> "bad" p jon #=> #<Person name="bad"> Uh oh... If you don't want this side effect—if you want to replace the string in the array with a different string, but not change the string itself–then you need to find the index of the item and update that: # Find the _first_ index matching some criteria and change it array[ array.index{ |s| s =~ /good/ } ] = "bad" # Update _every_ item in the array matching some criteria array[i] = "bad" while i = array.index{ |s| s =~ /good/i } # Another way to do the above # Possibly more efficient for very large arrays any many items indices = array.map.with_index{ |s,i| s =~ /good/ ? i : nil }.compact indices.each{ |i| array[i] = "bad" } Finally, the simplest and mostly fastest, without mucking about with indices: # Create a new array with the new values new_array = array.map do |s| if s =~ /good/i # matches "Good" or "good" in the string "bad" else s end end # Same thing, but shorter syntax new_array = array.map{ |s| s =~ /good/i ? "bad" : s } # Or, change the array in place to the new values new_array = array.map!{ |s| s =~ /good/i ? "bad" : s }

There's also a special method for this: array.grep(/good/) # => ["Ham is good"] With #grep you can do a lot because it takes a regular expression...

map! sounds like a good choice. x = ['i', 'am', 'good'] def change_string_to_your_liking s # or whatever it is you plan to do with s s.gsub('good', 'excellente!') end x.map! {|i| i =~ /good/ ? change_string_to_your_liking(i) : i} puts x.inspect