iOS设计模式 - 代理

原理图

说明

1. 代理模式大家都用过,但用抽象基类NSProxy实现代理估计鲜有人用

2. 本人用NSProxy实现了代理模式,对于理解消息转发机制有点帮助

源码

////  AbstractProxy.h//  AppProxy////  Created by YouXianMing on 15/8/4.//  Copyright (c) 2015年 YouXianMing. All rights reserved.//#import 
    
     @interface AbstractProxy : NSProxy/** *  被代理对象 */@property (nonatomic, weak) id  customer;/** *  代理客户 * *  @param customer 实现了某种协议的客户 * *  @return 代理对象 */- (instancetype)initWithCustomer:(id)customer;@end
    

////  AbstractProxy.m//  AppProxy////  Created by YouXianMing on 15/8/4.//  Copyright (c) 2015年 YouXianMing. All rights reserved.//#import 
    
     #import "AbstractProxy.h"#import "AbstractExcute.h"@implementation AbstractProxy- (instancetype)initWithCustomer:(id)customer {    self.customer = customer;    return self;}#pragma mark - NSProxy- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector {        if ([self.customer respondsToSelector:aSelector]) {                return [self.customer methodSignatureForSelector:aSelector];            } else {                AbstractExcute *excute = [AbstractExcute shareInstance];        return [excute methodSignatureForSelector:NSSelectorFromString(@"nullExcute:")];    }}- (void)forwardInvocation:(NSInvocation *)invocation {        SEL selector = [invocation selector];    if ([self.customer respondsToSelector:selector]) {                [invocation setTarget:self.customer];        [invocation invoke];            } else {            NSString *selectorString = NSStringFromSelector(invocation.selector);                invocation.selector    = NSSelectorFromString(@"nullExcute:");        AbstractExcute *excute = [AbstractExcute shareInstance];        [invocation setTarget:excute];                const char *className      = class_getName([self class]);        NSArray    *classNameArray = nil;        if (self.customer) {                        classNameArray = @[[NSString stringWithUTF8String:className], selectorString, @""];                    } else {                    classNameArray = @[[NSString stringWithUTF8String:className], selectorString];        }                [invocation setArgument:&classNameArray atIndex:2];        [invocation invoke];    }}@end
    

////  AbstractExcute.h//  AppProxy////  Created by YouXianMing on 15/8/4.//  Copyright (c) 2015年 YouXianMing. All rights reserved.//#import 
    
     @interface AbstractExcute : NSObject+ (instancetype)shareInstance;@end
    

////  AbstractExcute.m//  AppProxy////  Created by YouXianMing on 15/8/4.//  Copyright (c) 2015年 YouXianMing. All rights reserved.//#import "AbstractExcute.h"@implementation AbstractExcute+ (instancetype)shareInstance {    static AbstractExcute *sharedAbstractExcute = nil;        static dispatch_once_t predicate;    dispatch_once(&predicate, ^{        sharedAbstractExcute = [[self alloc] init];    });        return sharedAbstractExcute;}- (void)nullExcute:(NSArray *)className {    if (className.count == 3) {                NSLog(@"%@ 设置了代理,但该代理没有实现 %@ 方法", className[0], className[1]);            } else {            NSLog(@"%@ 没有设置代理,方法 %@ 没有执行", className[0], className[1]);    }    }@end

细节

NSProxy子类实现的关键所在