CODEWITHSUNDEEP
rubyrspec
Sean
Sean

Reputation: 3042

define method inside block

I'm new to ruby, I'm studying ruby by writing unittest with RSpec, and there is one line of code I can't understand in RSpec when define custom matcher.

RSpec::Matchers.define :be_a_multiple_of do |expected|
  match do |actual|
    do_the_math(actual, expected)
  end

  def do_the_math(actual, expected)
    actual % expected == 0
  end
end

as far as I know, ruby is a script language that the compiler read the code sequencly. that is said you must define the method before you use it. but in RSpec, when I define a custom matcher, I could define the helper method after I call it.

I have write the test code to test the fact that it will fail if I call the method before I define it and I also read a little source code from RSpec the define method actually is a wrapper of define_method and pass the delegate as block. but I still can't understand how this code work.

can somebody help me out? just a brief explaination of how this work

Upvotes: 1

Views: 1628

Answers (1)

BroiSatse
BroiSatse

Reputation: 44675

Short explanation is: you are not calling this method yet in there, you are only saying to call it when you call be_a_multiple_of matcher, and the method is already defined when that happens.

Parser is not checking whether methods are defined or not when declaring a method or block - as the method might be defined later or there might be a missing_method fall_back.

Upvotes: 1

Related Questions