EXC_BAD_ACCESS when accessing parameters in andDo of OCMock - iphone

Question

I am trying to write an block of code using OCMock's stub andDo method.
In this case UIImageView extension class is being tested. I want to check that the extension calls [self setImage:] with parameter that is non-nil (later other image comparison will be used).
When using OCMock's andDo method, the test crashes with EXC_BAD_ACCESS after the block completes.
id mockView = [OCMockObject mockForClass:[UIImageView class]];
[[[mockView stub] andDo:^(NSInvocation *invocation)
{
UIImage *img;
[invocation getArgument:&img atIndex:2]; <---- line causing the exception
somebodySetImage |= (img != nil);
}] setImage:OCMOCK_ANY];
[mockView do_something_that_calls_setImage];
The only solution that I've found for now is using andCall instead of andDo, but this complicates the test.
Can I avoid the crash with andDo?
UPDATE
Well, I will try to give a better example here:
Here is the new piece of the test code:
- (void)testDownloadingThumbnail
{
PInfo *_sut = [[PInfo alloc] init];
__block id target = nil;
id mock = [OCMockObject mockForClass:[NSOperationQueue class]];
[[[mock expect] andDo:^(NSInvocation *inv)
{
NSInvocationOperation *op;
[inv getArgument:&op atIndex:2];
target = [[op invocation] target]; /* replacing this line with STAssert does not help either */
}] addOperation:OCMOCK_ANY];
[_sut setDownloadQueue:mock];
[_sut startDownloadingImagesAsync:YES];
[mock verify];
STAssertEqualObjects(target, _sut, #"invalid op target");
}
Here is the tested code (single method from PInfo):
- (void)startDownloadingImagesAsync:(bool)isThumbnailImg
{
NSInvocationOperation *inv;
inv = [[NSInvocationOperation alloc] initWithTarget:self
selector:#selector(loadThumbnailWorker:)
object:nil];
[[self downloadQueue] addOperation:inv];
}
The code still crashes upon exit from startDownloadingImagesAsync with EXC_BAD_ACCESS.
If I add a breakpoint inside the andDo block, I see that the control reaches this point and retrieves correct objects via getArgument.
Yet, if I use getArgument inside the block, it crashes whatever I try to do.
P.S. Thanks for help.

Answer 1

I ran into a similar problem when using NSProxy's forwardInvocation: method.
Can you try the below?
NSInvocationOperation *op; // Change this line
__unsafe_unretained NSInvocationOperation *op; // to this line
Or another approach could be to retain NSInvocation's arguments:
[invocation retainArguments];
http://developer.apple.com/library/ios/documentation/Cocoa/Reference/Foundation/Classes/NSInvocation_Class/Reference/Reference.html#//apple_ref/occ/instm/NSInvocation/retainArguments
I'll try to add a more detailed explanation later.

Answer 2

I think the problem is that you're trying to invoke a mock object directly. For what you're trying to do, you shouldn't need a mock object. Just call the method and verify that the image was set:
expect(myObject.imageView.image).to.beNil();
[myObject do_something_that_calls_setImage];
expect(myObject.imageView.image).not.to.beNil();
If you really want to use a mock for some reason, you could do it with a real UIImageView and a partial mock:
UIImageView *imageView = myObject.imageView;
id mockView = [OCMockObject partialMockForObject:imageView];
__block BOOL imageSet = NO;
[[[mockView stub] andDo:^(NSInvocation *invocation) {
UIImage *img;
[invocation getArgument:&img atIndex:2];
imageSet = (img != nil);
}] setImage:OCMOCK_ANY];
[myObject do_something_that_calls_setImage];
expect(imageSet).to.beTruthy();

Answer 3

In my case this was happening because I introduced another parameter to this method, so the block parameter got shifted by one.
I fixed it by changing [inv getArgument:&op atIndex:2] to [inv getArgument:&op atIndex:3]