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:@"1"];[self.linkedList addItem:@"2"];[self.linkedList addItem:@"3"];[self.linkedList addItem:@"4"];[self.linkedList addItem:@"5"];// 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