消息转发封装

.h

@interface ForwardingProxy : NSProxy

@property (nonatomic, strong) id target;
- (instancetype)initWithTarget:(id)target;

@end


@interface TargetClass : NSObject

- (void)existingMethod;
- (void)anotherExistingMethod;

@end

#import "ForwardingProxy.h"

@implementation ForwardingProxy

- (instancetype)initWithTarget:(id)target {
    _target = target;
    return self;
}

- (BOOL)respondsToSelector:(SEL)aSelector {
    return [self.target respondsToSelector:aSelector];
}

- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector {
    NSMethodSignature *methodSignature = [self.target methodSignatureForSelector:aSelector];
    if (methodSignature) {
        return methodSignature;
    }
    return [NSMethodSignature signatureWithObjCTypes:"v@:"];
}

- (void)forwardInvocation:(NSInvocation *)anInvocation {
    SEL selector = anInvocation.selector;
    if ([self.target respondsToSelector:selector]) {
        [anInvocation invokeWithTarget:self.target];
    } else {
        [self handleUnknownSelector:selector];
    }
}

- (void)handleUnknownSelector:(SEL)selector {
    NSLog(@"Unknown selector: %@", NSStringFromSelector(selector));
}

@end


@implementation TargetClass

- (void)existingMethod {
    NSLog(@"Existing method called");
}
@end

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.

    TargetClass *target = [[TargetClass alloc] init];
    ForwardingProxy *proxy = [[ForwardingProxy alloc] initWithTarget:target];
    
    [proxy performSelector:@selector(existingMethod)];
    
    [proxy performSelector:@selector(nonExistentMethod)];
    
    [proxy performSelector:@selector(anotherExistingMethod)];

}

打印结果：
Invocation[3637:122461] Existing method called
Invocation[3637:122461] Unknown selector: nonExistentMethod
Invocation[3637:122461] Unknown selector: anotherExistingMethod

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    id target = NSClassFromString(@"Worker");
    ForwardingProxy *proxy = [[ForwardingProxy alloc] initWithTarget:target];
    [proxy performSelector:@selector(existingMethod)];
    [proxy performSelector:@selector(anotherExistingMethod)];
    
}