OC中的方法調(diào)用，其實(shí)都是轉(zhuǎn)換為objc_msgSend函數(shù)的調(diào)用

objc_msgSend的執(zhí)行流程可以分為3大階段

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動(dòng)態(tài)方法解析

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///

+（BOOL）resolveInstanceMethod:(SEL)sel

{

? If(sel == @selector(test)){

? Method method = class_getInstanceMethod(self,@selector(other));

class_addMethod(self,sel,method_getImplementation(method),

? method_getTypeEncoding(method));

? return YES；

? }

return [super resolveInstanceMethod:sel];

}

Void other(id self, SEL _cmd)

{

? NSLog(@“%@-%s-%s”,self,sel_getName(_cmd),__func__);

}

+(BOOL)resolveInstanceMethod:(SEL)sel

{

? If(sel == @selector(test)){

? class_addMethod(Self,sel,(IMP)other,@“v@:”);

? return YES；

? }

? return [super resolveInstanceMethod:sel];

}

///

Method 可以理解為等價(jià)于struct method_t*

生成NSMethodSignature

NSMethodSignature * signature = [NSMethodSignature signatureWithObjCTypes : “i@:i”];

NSMethodSignature * signature = [[[MJStudent alloc] init] methodSignatureForSelector:@selector(test:)];