iOS

高效编写代码-消息转发
深入了解runtime
NSInvocation介绍
NSHipster-Swizzling
Objective-C Method相关方法分析
Type Encodings

推荐阅读高效编写代码-消息转发。

在这里，我只针对一个经常出现的Crash给出利用消息转发处理的方案。

应用:处理Crash : unrecognized selector send to instance

@implementation NSObject (Swizzling)

+ (BOOL)lv_swizzlingInstanceOringnalSel:(SEL)orignalSel AletSel:(SEL)aletSel {
    
    if (!orignalSel || !aletSel) {
        return NO;
    }
    
    Class cls = [self class];
    
    Method orignalMethod = class_getInstanceMethod(cls, orignalSel);
    Method aletMethod    = class_getInstanceMethod(cls, aletSel);
    
    BOOL addAletMethod = class_addMethod(cls, aletSel,
                                         method_getImplementation(aletMethod),
                                         method_getTypeEncoding(aletMethod));
    if (addAletMethod) {
        class_replaceMethod(cls, aletSel,
                            method_getImplementation(orignalMethod),
                            method_getTypeEncoding(orignalMethod));
    }else {
        method_exchangeImplementations(orignalMethod, aletMethod);
    }
    return YES;
}

+ (BOOL)lv_swizzlingClassOrignalSel:(SEL)orignalSel AletSel:(SEL)aletSel {
    return [object_getClass((id)self) lv_swizzlingInstanceOringnalSel:orignalSel AletSel:aletSel];
}

@end

@implementation NSNull (NilSafe)

+ (void)load {
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        [self lv_swizzlingInstanceOringnalSel:@selector(methodSignatureForSelector:) AletSel:@selector(lv_methodSignatureForSelector:)];
        [self lv_swizzlingInstanceOringnalSel:@selector(forwardInvocation:) AletSel:@selector(lv_forwardInvocation:)];
    });
}

- (NSMethodSignature *)lv_methodSignatureForSelector:(SEL)aSelector {
    NSMethodSignature * sign = [self lv_methodSignatureForSelector:aSelector];
    if (sign) {
        return sign;
    }
    return [NSMethodSignature signatureWithObjCTypes:@encode(void)];
}

- (void)lv_forwardInvocation:(NSInvocation *)anInvocation {
    return;
}

@end