iOS设计模式 - 访问者

//
//  ElementProtocol.h
//  VisitorPattern
//
//  Created by YouXianMing on 15/10/27.
//  Copyright © 2015年 ZiPeiYi. All rights reserved.
//

#import <Foundation/Foundation.h>
@protocol VisitorProtocol;

@protocol ElementProtocol <NSObject>

/**
 *  接收访问者
 *
 *  @param visitor 访问者对象
 */
- (void)accept:(id <VisitorProtocol>)visitor;

/**
 *  元素公共的操作
 */
- (void)operation;

@end

//
//  VisitorProtocol.h
//  VisitorPattern
//
//  Created by YouXianMing on 15/10/27.
//  Copyright © 2015年 ZiPeiYi. All rights reserved.
//

#import <Foundation/Foundation.h>
#import "ElementProtocol.h"

@protocol VisitorProtocol <NSObject>

- (void)visitElement:(id <ElementProtocol>)element;

@end

//
//  ElementCollection.h
//  VisitorPattern
//
//  Created by YouXianMing on 15/10/27.
//  Copyright © 2015年 ZiPeiYi. All rights reserved.
//

#import <Foundation/Foundation.h>
@protocol ElementProtocol;

@interface ElementCollection : NSObject

/**
 *  添加元素
 *
 *  @param element 元素
 *  @param key     元素的键值
 */
- (void)addElement:(id <ElementProtocol>)element withKey:(NSString *)key;

/**
 *  获取所有元素的键值
 *
 *  @return 所有元素的键值
 */
- (NSArray *)allKeys;

/**
 *  根据元素键值获取元素
 *
 *  @param key 元素的键值
 *
 *  @return 元素
 */
- (id <ElementProtocol>)elementWithKey:(NSString *)key;

@end

//
//  ElementCollection.m
//  VisitorPattern
//
//  Created by YouXianMing on 15/10/27.
//  Copyright © 2015年 ZiPeiYi. All rights reserved.
//

#import "ElementCollection.h"
#import "ElementProtocol.h"

@interface ElementCollection ()

@property (nonatomic, strong) NSMutableDictionary  *elementsDictionary;

@end

@implementation ElementCollection

- (instancetype)init {
    
    self = [super init];
    
    if (self) {
    
        self.elementsDictionary = [NSMutableDictionary dictionary];
    }
    
    return self;
}

- (void)addElement:(id <ElementProtocol>)element withKey:(NSString *)key {

    NSParameterAssert(element);
    NSParameterAssert(key);
    
    [self.elementsDictionary setObject:element forKey:key];
}

- (NSArray *)allKeys {

    return self.elementsDictionary.allKeys;
}

- (id <ElementProtocol>)elementWithKey:(NSString *)key {

    NSParameterAssert(key);
    
    return [self.elementsDictionary objectForKey:key];
}

@end