Ruby: Merging variables in to a string

user_67113 0
Viewed 136723

I'm looking for a better way to merge variables into a string, in Ruby.

For example if the string is something like:

"The animal action the second_animal"

And I have variables for animal, action and second_animal, what is the prefered way to put those variables in to the string?

ruby string
7 Answers

The idiomatic way is to write something like this:

"The #{animal} #{action} the #{second_animal}"

Note the double quotes (") surrounding the string: this is the trigger for Ruby to use its built-in placeholder substitution. You cannot replace them with single quotes (') or the string will be kept as is.

Mike_Woodhouse_10600

You can use sprintf-like formatting to inject values into the string. For that the string must include placeholders. Put your arguments into an array and use on of these ways: (For more info look at the documentation for Kernel::sprintf.)

fmt = 'The %s %s the %s'
res = fmt % [animal, action, other_animal]  # using %-operator
res = sprintf(fmt, animal, action, other_animal)  # call Kernel.sprintf

You can even explicitly specify the argument number and shuffle them around:

'The %3$s %2$s the %1$s' % ['cat', 'eats', 'mouse']

Or specify the argument using hash keys:

'The %{animal} %{action} the %{second_animal}' %
  { :animal => 'cat', :action=> 'eats', :second_animal => 'mouse'}

Note that you must provide a value for all arguments to the % operator. For instance, you cannot avoid defining animal.

gix_548250

You can use it with your local variables, like this:

@animal = "Dog"
@action = "licks"
@second_animal = "Bird"

"The #{@animal} #{@action} the #{@second_animal}"

the output would be: "The Dog licks the Bird"

user_88574270
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