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NVMAspects

About

Yet another AOP library for Objective-C, but implement by using libffi. The main goal for this lib is to avoid heavily use of forwardInvocation, powerful, easy to use and also easy to read.

This lib is inspired by Aspects, JSPatch, NSBlog and sunnyxx's blog, thanks all these people.

Example

A simple example is look like this, provide a block to replace the original implementation, look very similar to Aspects but have a bit difference. You can alter the arguments or return value by modify info.invocation. If you aren't sure the existing of original implementation, you should call class_addPlaceholderIfNoImplement fisrt.

[[UIImage nvm_hookInstanceMethod:@selector(imageNamed:)
                      usingBlock:^void(NVMAspectInfo *info, NSString *name) {
                        NSLog(@"Load image named %@", name);
                        [info.invocation invoke];
                      }];

Notes

  • Actually there are some bugs on this lib, Bit Field, Union, Struct contain array. But bit field and union are also not well supportted by apple's NSInvocation, struct contain small array is a bug in libffi. All these features used very rare in Objective-C, so it's not a big problem.

  • NVMAspects doesn't forbidden you to hook any method, but if you make some changes to method like alloc, you should follow the memory management policy, especially in ARC.

  • Currently if a class has defined a method, hook this method will change it's imp, even if that method is implemented by it's super class. But this is not a big problem, you can distinguish the class by test [self class] in you block. If the class has not defined a method, you should call class_addPlaceholderIfNoImplement first.

  • For problem caused by forwardInvocation, you can use this keyword to search issues in Aspects or JSPatch.

Installation

add the following line to your Podfile:

pod "NVMAspects"

License

NVMAspects is released under the MIT license.