Module: RSpec::Core::Let::ClassMethods

Defined in:
lib/rspec/core/let.rb

Instance Method Summary collapse

Instance Method Details

#let(name, &block) ⇒ Object

Generates a method whose return value is memoized after the first call.

Examples

describe Thing do let(:thing) { Thing.new }

it "does something" do
 # first invocation, executes block, memoizes and returns result
 thing.do_something

 # second invocation, returns the memoized value
 thing.should be_something
end

end



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# File 'lib/rspec/core/let.rb', line 22

def let(name, &block)
  define_method(name) do
    __memoized[name] ||= instance_eval(&block)
  end
end

#let!(name, &block) ⇒ Object

Just like let(), except the block is invoked by an implicit before hook. This serves a dual purpose of setting up state and providing a memoized reference to that state.

Examples

class Thing def self.count @count ||= 0 end

def self.count=(val)
 @count += val
end

def self.reset_count
 @count = 0
end

def initialize
 self.class.count += 1
end

end

describe Thing do after(:each) { Thing.reset_count }

context "using let" do
 let(:thing) { Thing.new }

 it "is not invoked implicitly" do
   Thing.count.should == 0
 end

 it "can be invoked explicitly" do
   thing
   Thing.count.should == 1
 end
end

context "using let!" do
 let!(:thing) { Thing.new }

 it "is invoked implicitly" do
   Thing.count.should == 1
 end

 it "returns memoized version on first invocation" do
   thing
   Thing.count.should == 1
 end
end

end



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# File 'lib/rspec/core/let.rb', line 82

def let!(name, &block)
  let(name, &block)
  before { __send__(name) }
end