Using runtime to change the implementation of system methods

? Usage scenarios:

? ? In the project, we may encounter the need to modify the implementation of the method, such as the need to replace some of the original implementation code, but if the project size is large, then manually find the replacement method is not available. The better way is to replace it with runtime.

The simplest, rather than the film, assumes that the method we used before is [UIImage imagenamed:@ "]

But now our picture changed, the image suffix batch added a _os8, below we see how the code implementation:

Special attention:

In our custom method, we have exchanged system methods and custom methods, so the custom method wants to call the system method and, in fact, should call itself. (Looks like a dead cycle ha)

Using runtime to change the implementation of system methods