hook大体思路：

1.对微信自定义的WCActionSheet的初始化方法去hook，添加一项保存视频的功能
2.对WCActionSheet的代理方法进行hook，找到点击代理方法
至于怎么获取WCActionSheet里面有哪些方法，方法参数是什么。

如果你没有越狱的手机的话，也可以去PP助手上下一个越狱版的微信，然后用class-dump出头文件来看看

在此特别感谢蒸米、east520 、dskcpp

开始吧！！！！！

1.编译生成dylib

通过iOSOpendev来创建一个Cocoa Touch Library项目
这个具体就可以参考上面那个抢红包的博客了

#import "CaptainHook.h"
#import <JSPatch/JSPatch.h>
CHDeclareClass(MicroMessengerAppDelegate);

CHMethod(2, BOOL, MicroMessengerAppDelegate, application, id, arg1, didFinishLaunchingWithOptions, id, arg2)
{
  BOOL supBool = CHSuper(2, MicroMessengerAppDelegate, application, arg1, didFinishLaunchingWithOptions, arg2);
  [JSPatch startWithAppKey:@"xxxxxx"];
  [JSPatch sync];
  return supBool;
}

__attribute__((constructor)) static void entry()
{
  CHLoadLateClass(MicroMessengerAppDelegate);
  CHHook(2, MicroMessengerAppDelegate, application, didFinishLaunchingWithOptions);
}

command+b 编译一下，可以在Product下面看到你编译成功的dylib了 copy出来

2.注入dylib到WeChat

把PP助手上下的越狱版的微信解压后在Payload/WeChat.app/WeChat复制出来
通过yolo 把dylib注入到WeChat里面

./yolo WeChat xxx.dylib

然后把注入后的WeChat和xxx.dylib复制回Payload/WeChat.app/ 替换掉原来的WeChat

然后就是重新签名打包安装了，这块操作参考刚上面说的几篇博客

3.编写JSPatch文件，下发补丁

require('WCContentItemViewTemplateNewSight, WCActionSheet,ALAssetsLibrary,NSURL')

defineClass('WCActionSheet', {
initWithTitle_delegate_cancelButtonTitle_destructiveButtonTitle_otherButtonTitles:function(arg1,arg2,arg3,arg4,arg5) {
            console.log("arg2 00000>>>>>>>>"+arg2);
            var actionSheet = self.ORIGinitWithTitle_delegate_cancelButtonTitle_destructiveButtonTitle_otherButtonTitles(arg1,arg2,arg3,arg4,arg5);
            //不知道为什么在arm64的情况下 点击朋友圈切换封面的时候会导致微信崩溃报错误 <Error>: unable to find offset 0x9b213a5c in shared cache for arch 'arm64'
            //但是下面IF判断全部注释，也一样会崩，但是我只要把第二句log也注释，就不会报错。这个问题我也不是很清楚，毕竟我也没有微信源码
            console.log("arg2 11111>>>>>>>>"+arg2);
            if (arg2.isKindOfClass(WCContentItemViewTemplateNewSight.class())) {
                actionSheet.addButtonWithTitle("保存视频");
            }
            return actionSheet;
        }
});

defineClass('WCContentItemViewTemplateNewSight', {
    actionSheet_clickedButtonAtIndex:function(arg1,arg2) {
        var buttonTitleList = arg1.buttonTitleList().toJS();
        console.log("buttonTitleList>>>>>>>>"+buttonTitleList);
        var btnTitle = buttonTitleList[arg2];
        console.log("btnTitle>>>>>>>>"+btnTitle);
        if (btnTitle == "保存视频") {
            var dmsightVideoPath = self.sightVideoPath();
            console.log("sightVideoPath>>>>>>>>"+dmsightVideoPath);
            if (dmsightVideoPath) {
                var dmlibrary = ALAssetsLibrary.alloc().init();
                var dmVideoPathURL = NSURL.fileURLWithPath(dmsightVideoPath); 
                dmlibrary.writeVideoAtPathToSavedPhotosAlbum_completionBlock(dmVideoPathURL, block('NSURL*,NSError*', function(assetURL, error) {
                    console.log("save video>>>>>"+error.toJS());
                }));
             }
         } else { 
            console.log("btnTitle != 保存视频");
            self.ORIGactionSheet_clickedButtonAtIndex(arg1,arg2);
         }
    }
});

不过这个插件还有点小问题
bug：
在重写WCActionSheet的
initWithTitle:delegate:cancelButtonTitle:destructiveButtonTitle:otherButtonTitles的时候

不知道为什么在arm64的情况下 点击朋友圈切换封面的时候会导致微信崩溃报错误
<Error>: unable to find offset 0x9b213a5c in shared cache for arch 'arm64'
IF判断全部注释，也一样会崩。这个问题我也不是很清楚，毕竟我也没有微信源码

下面这种情况也会崩

defineClass('WCActionSheet', {
initWithTitle_delegate_cancelButtonTitle_destructiveButtonTitle_otherButtonTitles:function(arg1,arg2,arg3,arg4,arg5) {
            console.log("arg2 00000>>>>>>>>"+arg2);
            var actionSheet = self.ORIGinitWithTitle_delegate_cancelButtonTitle_destructiveButtonTitle_otherButtonTitles(arg1,arg2,arg3,arg4,arg5);      
            console.log("arg2 11111>>>>>>>>"+arg2);
            return actionSheet;
        }
});

但是把后面的那句log去掉就不会崩

defineClass('WCActionSheet', {
initWithTitle_delegate_cancelButtonTitle_destructiveButtonTitle_otherButtonTitles:function(arg1,arg2,arg3,arg4,arg5) {
            console.log("arg2 00000>>>>>>>>"+arg2);
            var actionSheet = self.ORIGinitWithTitle_delegate_cancelButtonTitle_destructiveButtonTitle_otherButtonTitles(arg1,arg2,arg3,arg4,arg5);      
            return actionSheet;
        }
});