+(void)load{
static dispatch_once_t onceToken;
dispatch_once(&onceToken,^{
[LGRuntimeTool lg_methodSwizzlingWithClass:selforiSEL:@selector(personInstanceMethod)swizzledSEL:@selector(lg_studentInstanceMethod)];
});
}
+ (void)lg_bestMethodSwizzlingWithClass:(Class)cls oriSEL:(SEL)oriSEL swizzledSEL:(SEL)swizzledSEL{
if (!cls) NSLog(@"传入的交换类不能为空");
Method oriMethod = class_getInstanceMethod(cls, oriSEL);
Method swiMethod = class_getInstanceMethod(cls, swizzledSEL);
if (!oriMethod) {
// 在oriMethod为nil时，替换后将swizzledSEL复制一个不做任何事的空实现,代码如下:
class_addMethod(cls, oriSEL, method_getImplementation(swiMethod), method_getTypeEncoding(swiMethod)); method_setImplementation(swiMethod, imp_implementationWithBlock(^(id self, SEL _cmd){ }));
}
// 一般交换方法: 交换自己有的方法 -- 走下面 因为自己有意味添加方法失败 // 交换自己没有实现的方法: // 首先第一步:会先尝试给自己添加要交换的方法 :personInstanceMethod (SEL) -> swiMethod(IMP) // 然后再将父类的IMP给swizzle personInstanceMethod(imp) -> swizzledSEL //oriSEL:personInstanceMethod
BOOL didAddMethod = class_addMethod(cls, oriSEL, method_getImplementation(swiMethod), method_getTypeEncoding(swiMethod));
if (didAddMethod) {
class_replaceMethod(cls, swizzledSEL, method_getImplementation(oriMethod), method_getTypeEncoding(oriMethod));
}else{
method_exchangeImplementations(oriMethod, swiMethod);
}
}
method-swizzling最常用的应用是防止数组、字典等越界崩溃
NSArray --> __NSArrayI
NSMutableArray --> __NSArrayM
NSDictionary --> __NSDictionaryI
NSMutableDictionary --> __NSDictionaryM
