Replace each value in array with new value (Ruby)

Question

prefix = "!"    

commands = [
        "command_1",
        "command_2"]

commands.each do |command|
    command = prefix + command
end

This is pretty straightforward. I want to change the strings "command_1" & "command_2" to "!command_1" & "!command_2". How would I do that?

The reason that this does not work is that String#+ results in a new string. The old strings just keep sitting unaltered in the commands array. Choose map to store the new strings in a new array, or choose a method which mutates the strings, as the answers and comments indicate. — steenslag
– steenslag, Commented Apr 23, 2018 at 20:29

Ursus · Accepted Answer · 2018-04-23 18:43:48Z

3

use map

commands_with_prefix = commands.map { |command| prefix + command }

or map! to update the array in-place

commands.map! { |command| prefix + command }

another way, interpolation

commands.map! { |command| "#{prefix}#{command}" }

answered Apr 23, 2018 at 18:43

Ursus

30.1k3 gold badges36 silver badges52 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

engineersmnky Over a year ago

Or String#replace e.g. commands.each {|c| c.replace("#{prefix}#{c}") }

engineersmnky Over a year ago

@steenslag that is much better although you could always c.sub!(/\A/,prefix) :)

Thirumal Sakthivel Over a year ago

@Tearzz commands.each { |command| command.insert(0, prefix) }

TheVinspro Over a year ago

commands_with_prefix = commands.map { |command| "!" << command } as + operator returns a new String each time while << on the other hand concatenates to the given object.

Ursus Over a year ago

Thanks to everyone :)

Collectives™ on Stack Overflow

Replace each value in array with new value (Ruby)

1 Answer 1

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related