iOS设计模式 - 迭代器

iOS设计模式 - 迭代器

原理图

说明

提供一种方法顺序访问一个聚合对象中的各种元素，而又不暴露该对象的内部表示。

源码

https://github.com/YouXianMing/iOS-Design-Patterns

//
//  Node.h
//  IteratorPattern
//
//  Created by YouXianMing on 15/10/26.
//  Copyright © 2015年 YouXianMing. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface Node : NSObject

/**
 *  下一个节点
 */
@property (nonatomic, strong) Node *nextNode;

/**
 *  节点里面的内容
 */
@property (nonatomic, strong) id    item;

/**
 *  初始化节点
 *
 *  @param item 节点携带的内容
 *
 *  @return 节点
 */
- (instancetype)initWithItem:(id)item;

@end

//
//  Node.m
//  IteratorPattern
//
//  Created by YouXianMing on 15/10/26.
//  Copyright © 2015年 YouXianMing. All rights reserved.
//

#import "Node.h"

@implementation Node

- (instancetype)initWithItem:(id)item {

    self = [super init];

    if (self) {

        self.item = item;
    }

    return self;
}

@end

//
//  LinkedList.h
//  IteratorPattern
//
//  Created by YouXianMing on 15/10/26.
//  Copyright © 2015年 YouXianMing. All rights reserved.
//

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

#import "IteratorProtocol.h"
#import "LinkedListIterator.h"

@interface LinkedList : NSObject

/**
 *  头结点
 */
@property (nonatomic, strong, readonly) Node      *headNode;

/**
 *  节点的数目
 */
@property (nonatomic, assign, readonly) NSInteger  numberOfNodes;

/**
 *  添加数据
 *
 *  @param item 数据
 */
- (void)addItem:(id)item;

/**
 *  创建迭代器对象
 *
 *  @return 迭代器对象
 */
- (id <IteratorProtocol>)createIterator;

@end

//
//  LinkedList.m
//  IteratorPattern
//
//  Created by YouXianMing on 15/10/26.
//  Copyright © 2015年 YouXianMing. All rights reserved.
//

#import "LinkedList.h"

@interface LinkedList ()

/**
 *  头结点
 */
@property (nonatomic, strong, readwrite) Node      *headNode;

/**
 *  节点的数量
 */
@property (nonatomic, assign, readwrite) NSInteger  numberOfNodes;

@end

@implementation LinkedList

- (void)addItem:(id)item {

    if (self.headNode == nil) {

        self.headNode = [[Node alloc] initWithItem:item];

    } else {

        [self addItem:item node:self.headNode];
    }

    self.numberOfNodes++;
}

- (id <IteratorProtocol>)createIterator {

    return [[LinkedListIterator alloc] initWithLinkedList:self];
}

#pragma mark - Private Methods
- (void)addItem:(id)item node:(Node *)node {

    if (node.nextNode == nil) {

        node.nextNode = [[Node alloc] initWithItem:item];

    } else {

        [self addItem:item node:node.nextNode];
    }
}

@end

//
//  LinkedListIterator.h
//  IteratorPattern
//
//  Created by YouXianMing on 15/10/26.
//  Copyright © 2015年 YouXianMing. All rights reserved.
//

#import <Foundation/Foundation.h>
#import "IteratorProtocol.h"
@class LinkedList;

@interface LinkedListIterator : NSObject <IteratorProtocol>

/**
 *  由链表进行初始化
 *
 *  @param linkedList 链表对象
 *
 *  @return 迭代器工具
 */
- (id)initWithLinkedList:(LinkedList *)linkedList;

@end

//
//  LinkedListIterator.m
//  IteratorPattern
//
//  Created by YouXianMing on 15/10/26.
//  Copyright © 2015年 YouXianMing. All rights reserved.
//

#import "LinkedListIterator.h"
#import "LinkedList.h"

@interface LinkedListIterator ()

@property (nonatomic, weak) LinkedList *linkedList;
@property (nonatomic, weak) Node       *currentNode;

@end

@implementation LinkedListIterator

- (id)initWithLinkedList:(LinkedList *)linkedList {

    if (self = [super init]) {

        self.linkedList  = linkedList;
        self.currentNode = linkedList.headNode;
    }

    return self;
}

- (id)next {

    id item          = self.currentNode.item;
    self.currentNode = self.currentNode.nextNode;

    return item;
}

- (BOOL)hasNext {

    if (self.currentNode == nil) {

        return NO;

    } else {

        return YES;
    }
}

- (id)item {

    return self.currentNode.item;
}

@end

//
//  IteratorProtocol.h
//  IteratorPattern
//
//  Created by YouXianMing on 15/10/26.
//  Copyright © 2015年 YouXianMing. All rights reserved.
//

#import <Foundation/Foundation.h>

@protocol IteratorProtocol <NSObject>

/**
 *  下一个对象
 *
 *  @return 对象
 */
- (id)next;

/**
 *  是否存在下一个对象
 *
 *  @return 对象
 */
- (BOOL)hasNext;

/**
 *  内容
 *
 *  @return 返回内容
 */
- (id)item;

@end

//
//  ViewController.m
//  IteratorPattern
//
//  Created by YouXianMing on 15/10/26.
//  Copyright © 2015年 YouXianMing. All rights reserved.
//

#import "ViewController.h"

#import "LinkedList.h"
#import "LinkedListIterator.h"

@interface ViewController ()

@property (nonatomic, strong) LinkedList  *linkedList;

@end

@implementation ViewController

- (void)viewDidLoad {

    [super viewDidLoad];

    // 创建链表结构
    self.linkedList = [[LinkedList alloc] init];

    // 添加链表元素
    [self.linkedList addItem:@""];
    [self.linkedList addItem:@""];
    [self.linkedList addItem:@""];
    [self.linkedList addItem:@""];
    [self.linkedList addItem:@""];

    // 创建迭代器
    id <IteratorProtocol> iterator = [self.linkedList createIterator];

    // 进行元素迭代
    while ([iterator hasNext]) {

        NSLog(@"%@", iterator.item);
        [iterator next];
    }
}

@end

细节