Hook Objective-C method

In Windows, there are two main types of hooks: Message hooks and function hooks. Sometimes you must use hooks when implementing some functions.

The function hook is mainly used to replace the entry address. In a broad sense, many things are hooks, such as the interrupt vector table.

It is possible to hook static and virtual functions in C ++, but it is difficult to hook common functions mainly because C ++ does not have a unified ABI standard.

However, you can use Objective-C hooks, and OC provides some runtime methods to make them relatively simple. For example, you do not need to use assembler to change the address.

The following uses the loadRequest: hook sub for UIWebView as an example to illustrate how to use the hook sub in Objective-C.

Class Name: UIWebView

Method Name: loadRequest:

Corresponding C prototype:

Typedef void (* UIWebView_loadRequest _ IMP) (UIWebView * self, SEL _ cmd, NSURLRequest * request );

Static UIWebView_loadRequest _ IMP original_UIWebView_loadRequest;

Void replaced_UIWebView_loadRequest (UIWebView * self, SEL _ cmd, NSURLRequest * request ){

Original_UIWebView_loadRequest (self, _ cmd, request );

// TODO:

}

// Add the following code to a vertex, such as application: didfinishlaunchingwitexceptions: to complete the hook.

Method method = class_getInstanceMethod (NSClassFromString (@ "UIWebView"), @ selector (loadRequest :));

Original_UIWebView_loadRequest = method_setImplementation (method, replaced_UIWebView_loadRequest );

Application scenarios:

Let's think about it. ^_^