Ruby: Merging variables in to a string
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?
Solution 1:
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.
Solution 2:
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
.