gistfile1.matlab

# File: MainView.m

[Doorman requestUnlockDoor:^(BOOL successfulRequest) {
  if (successfulRequest) {
    // do stuff
  }
  else {
    // do other stuff
  }
}];


# File: Doorman.m

@implementation Doorman

+ (void)requestUnlockDoor:(void(^)(BOOL successfulRequest))completionHandler {
    completionHandler(FALSE);
}

@end

1.9.3p286 :001 > completionHandler = proc { |successfulRequest| puts "successful request is #{successfulRequest}" }
 => #<Proc:0x007f8c3b843950@(irb):1>
1.9.3p286 :002 > completionHandler.(true)
successful request is true
 => nil
1.9.3p286 :003 > completionHandler.(false)
successful request is false
 => nil

class Doorman
  def self.open_door(&block)
      block.call true #or false
end

Doorman.open_door do |success|
  if success
    puts "success"
  else
    puts "failure"
  end
end