Capturing arguments?

[codyaray]

Is there a mechanism to capture arguments?

Most asynchronous APIs (especially for networking libraries) accept completion blocks. It'd be awesome to be able to capture the completion block and test against it.

For example, suppose I mock a NSURLConnector. (Thanks for showing me we can mock class methods earlier today on StackOverflow!) Then I want to verify that my code calls sendAsynchronousRequest:queue:completionHandler. I'd love to capture the completionBlock and verify the operations in the completion handler.

myblock = //... something I can test against
[verify(connector) sendAsynchronousRequest:urlRequest queue:queue completionHandler:capture(myblock)];

This request is similar to this request for Kiwi.

[jonreid]

Argument capturing isn't present today, but has been on my wish list.

[codyaray]

@jonreid - are we any closer to this elusive dream? :)

[crispinb]

Another reason for wanting argument capture is that it makes it possible to then use asserts on the captured arguments. These are more informative on failure than the messages emitted when using hamcrest matchers directly in a verify().

[jonreid]

I've started on this

[jonreid]

Give it a try! See ArgumentCaptorTest.m for examples.