iOS - 消息转发处理

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