Careful when calling a Ruby block with an array

When a Ruby block or proc takes multiple parameters, and you call it with an Array, Ruby will unexpectedly splat the array elements:

block = proc { |a, b| "a=#{a}, b=#{b}" }
block.call(1, 2)   # "a=1, b=2"
block.call([1, 2]) # "a=1, b=2"

Note that lambdas behave as expected:

block = lambda { |a, b| "a=#{a}, b=#{b}" }
block.call(1, 2)   # "a=1, b=2"
block.call([1, 2]) # ArgumentError: wrong number of arguments (1 for 2)

Henning Koch

License

Source code in this card is licensed under the MIT License.

Posted by Henning Koch to makandra dev (2013-12-17 13:36)