迭代器模式

迭代器模式定义

• 提供一种方法，按照顺序访问一个容器中对象的各个元素，而又不需要暴露该容器的内部细节（内部表示）

迭代器模式应用场景

• 遍历容器对象

迭代器模式角色划分

4个核心角色
角色一：Iterator(迭代器接口)->协议
作用： 定义了访问遍历元素的方法（标准）
角色二：Concreteiterator(具体迭代器)
作用：遍历具体元素方法实现
角色三：Aggregate(容器接口)->协议
作用：定义了存储元素的接口
角色四：concreteAggregate（具体容器）
作用：实现了存储元素的接口

注意：以后在框架设计或项目开发中，发现有遍历元素的场景，第一时间想到的就是迭代器模式（OC，swift，c++,java,kotlin等）

迭代器原理案例

遍历元素

抽象迭代器

//
//  IteratorProtocol.swift
//  Dream_20180716_Cursor
//
//  Created by Dream on 2018/7/16.
//  Copyright © 2018年 Tz. All rights reserved.
//

import Foundation

protocol IteratorProtocol {
    //两个方法
    //下一个元素(元素类型我们不知道->具体类型->泛型)->ItemType
    //associatedtype->声明Swift泛型关键字
    associatedtype ItemType
    func next() -> ItemType?
    //是否有元素
    func hasNext() -> Bool
}

具体迭代器

//
//  ConcreteIterator.swift
//  Dream_20180716_Cursor
//
//  Created by Dream on 2018/7/16.
//  Copyright © 2018年 Tz. All rights reserved.
//

import Cocoa

//什么是泛型？定义的时候不需要指定类型，使用的时候指定类型
class ConcreteIterator<T>: AnyIterator<T> {

    override func next() -> T? {
        if self.hasNext() {
            let result = self.array[index]
            index += 1
            return result
        }
        return nil
    }
    
    override func hasNext() -> Bool {
        return index != self.array.count
    }
    
}

抽象类型

//
//  AnyIterator.swift
//  Dream_20180716_Cursor
//
//  Created by Dream on 2018/7/16.
//  Copyright © 2018年 Tz. All rights reserved.
//

import Cocoa

class AnyIterator<T>: IteratorProtocol {

    typealias ItemType = T
    
    //记录当前遍历位置
    var index:Int = 0
    
    var array:Array<T>
    
    init(array:Array<T>) {
        self.array = array
    }
    
    func next() -> T? {
        return nil
    }
    
    func hasNext() -> Bool {
        return false
    }
    
}

抽象容器

//
//  AggregrateProtocol.swift
//  Dream_20180716_Cursor
//
//  Created by Dream on 2018/7/16.
//  Copyright © 2018年 Tz. All rights reserved.
//

import Foundation


//容器：保存数据类型->泛型
//强调一次：如果你对泛型不了解，那么赶紧复习，后面数据库框架设计全部都是泛型
protocol AggregrateProtocol {
    associatedtype DataType
    //添加元素
    func add(data:DataType)
    //删除元素
    func remove(index:Int) -> DataType
    //迭代器
    //注意：协议使用不允许指定类型->必需是实现类(语法规定)
    func iterator() -> AnyIterator<DataType>
}

具体容器

//
//  ConcreteAggregrate.swift
//  Dream_20180716_Cursor
//
//  Created by Dream on 2018/7/16.
//  Copyright © 2018年 Tz. All rights reserved.
//

import Cocoa

class ConcreteAggregrate<D>: AggregrateProtocol {
    //DataType给他定义一个别名
    typealias DataType = D
    private var array = Array<D>()
    
    func add(data: D) {
        self.array.append(data)
    }
    
    func remove(index: Int) -> D {
        return self.array.remove(at: index)
    }
    
    func iterator() -> AnyIterator<D> {
        //初始化(将数组传递到我们的迭代器中，由我们的迭代器来遍历元素)
        return ConcreteIterator<D>(array: self.array)
    }
    
}

具体实现

//
//  main.swift
//  Dream_20180716_Cursor
//
//  Created by Dream on 2018/7/16.
//  Copyright © 2018年 Tz. All rights reserved.
//

import Foundation

//测试
let a = "世界旁观者"
let b = "大吉大利"
let c = "NSLog"
//自己写的容器框架
let aggregrate = ConcreteAggregrate<String>()
aggregrate.add(data: a)
aggregrate.add(data: b)
aggregrate.add(data: c)

let iterator = aggregrate.iterator()
while iterator.hasNext(){
    let result = iterator.next()
    //得到这个元素(打印可能为nil，需要指定一个默认值->语法)
    print("结果:\(result ?? "")")
}

打印结果

结果:世界旁观者
结果:大吉大利
结果:NSLog

迭代器模式-oc加深版

OrderModel数据模型

//
//  OrderModel.h
//  Andy_20190308_iterator
//
//  Created by 王宁 on 2019/3/8.
//  Copyright © 2019年 王宁. All rights reserved.
//

#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

@interface OrderModel : NSObject
@property(nonatomic,strong)NSString *orderId;
@property(nonatomic,strong)NSString *orderName;
@property(nonatomic,strong)NSString *orderPrice;
@property(nonatomic,strong)NSString *orderDetail;

- (instancetype)initWithorderId:(NSString*)orderId orderName:(NSString*)orderName orderPrice:(NSString*)orderPrice orderDetail:(NSString*)orderDetail;
@end

NS_ASSUME_NONNULL_END

//
//  OrderModel.m
//  Andy_20190308_iterator
//
//  Created by 王宁 on 2019/3/8.
//  Copyright © 2019年 王宁. All rights reserved.
//

#import "OrderModel.h"

@implementation OrderModel

- (instancetype)initWithorderId:(NSString*)orderId orderName:(NSString*)orderName orderPrice:(NSString*)orderPrice orderDetail:(NSString*)orderDetail
{
  
    if ((self = [super init])) {
        self.orderId=orderId;
        self.orderName=orderName;
        self.orderPrice=orderPrice;
        self.orderDetail=orderDetail;
    }
 
    return self;
}




@end

抽象迭代器

//
//  IteratorProtocol.h
//  Andy_20190308_iterator
//
//  Created by 王宁 on 2019/3/8.
//  Copyright © 2019年 王宁. All rights reserved.
//

#import <Foundation/Foundation.h>
#import "OrderModel.h"
NS_ASSUME_NONNULL_BEGIN
//创造迭代器
@protocol IteratorProtocol <NSObject>

-(OrderModel*)next;

-(BOOL)hasNext;

@end

NS_ASSUME_NONNULL_END

抽象公用参数

//
//  OrderIterator.h
//  Andy_20190308_iterator
//
//  Created by 王宁 on 2019/3/8.
//  Copyright © 2019年 王宁. All rights reserved.
//

#import <Foundation/Foundation.h>
#import "IteratorProtocol.h"
NS_ASSUME_NONNULL_BEGIN

@interface OrderIterator<T>: NSObject<IteratorProtocol>
{
    int Index;
}
@property(nonatomic,strong)T obj;



- (instancetype)initWithObj:(T)obj;


@end

NS_ASSUME_NONNULL_END

//
//  OrderIterator.m
//  Andy_20190308_iterator
//
//  Created by 王宁 on 2019/3/8.
//  Copyright © 2019年 王宁. All rights reserved.
//

#import "OrderIterator.h"

@interface OrderIterator()

@end
@implementation OrderIterator

- (instancetype)initWithObj:(id)obj
{
    self = [super init];
    if (self) {
        self.obj=obj;
        Index=0;
    }
    return self;
}


- (BOOL)hasNext {
    return false;
}

- (nonnull OrderModel *)next {
    return nil;
}

@end

具体迭代器

//
//  TianMaoOrderIterator.h
//  Andy_20190308_iterator
//
//  Created by 王宁 on 2019/3/8.
//  Copyright © 2019年 王宁. All rights reserved.
//

#import <Foundation/Foundation.h>
#import "OrderIterator.h"
#import "OrderModel.h"
NS_ASSUME_NONNULL_BEGIN

@interface TianMaoOrderIterator: OrderIterator

@property(nonatomic,strong) NSEnumerator<OrderModel *> *iterator;

- (instancetype)initWIthSet:(NSSet<OrderModel*>*)set;
@end

NS_ASSUME_NONNULL_END

//
//  TianMaoOrderIterator.m
//  Andy_20190308_iterator
//
//  Created by 王宁 on 2019/3/8.
//  Copyright © 2019年 王宁. All rights reserved.
//

#import "TianMaoOrderIterator.h"

@implementation TianMaoOrderIterator

- (instancetype)initWIthSet:(NSSet<OrderModel*>*)set
{
    self = [super initWithObj:set];
    if (self) {
        self.iterator=set.objectEnumerator;
    }
    return self;
}


- (OrderModel *)next
{
      if([self hasNext])
      {
          OrderModel* result = self.iterator.nextObject;
          Index += 1;
          return result;
          
      }
    return nil;
}

- (BOOL)hasNext
{
   NSSet *set=(NSSet<OrderModel*>*)self.obj;
    return Index!=set.count;
}
@end

具体容器

//
//  TianmaoOrderAggregrate.h
//  Andy_20190308_iterator
//
//  Created by 王宁 on 2019/3/8.
//  Copyright © 2019年 王宁. All rights reserved.
//

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

#import "TianMaoOrderIterator.h"
NS_ASSUME_NONNULL_BEGIN

@interface TianmaoOrderAggregrate : NSObject
@property(nonatomic,strong)NSMutableSet<OrderModel*>*set;
- (id<IteratorProtocol>)iterator;
@end

NS_ASSUME_NONNULL_END

//
//  TianmaoOrderAggregrate.m
//  Andy_20190308_iterator
//
//  Created by 王宁 on 2019/3/8.
//  Copyright © 2019年 王宁. All rights reserved.
//

#import "TianmaoOrderAggregrate.h"

@implementation TianmaoOrderAggregrate
- (instancetype)init
{
    self = [super init];
    if (self) {
        self.set=[[NSMutableSet alloc]init];
       
        [self.set addObject:[[OrderModel alloc]initWithorderId:@"1" orderName:@"mac pro" orderPrice:@"2222" orderDetail:@"dddd"]];
          [self.set addObject:[[OrderModel alloc]initWithorderId:@"2" orderName:@"mac pro" orderPrice:@"2222" orderDetail:@"dddd"]];
          [self.set addObject:[[OrderModel alloc]initWithorderId:@"3" orderName:@"mac pro" orderPrice:@"2222" orderDetail:@"dddd"]];
        
     
    }
    return self;
}

- (id<IteratorProtocol>)iterator
{
    return  [[TianMaoOrderIterator alloc]initWIthSet:self.set];
}

@end

具体容器

//
//  JingdongOrderAggregrate.h
//  Andy_20190308_iterator
//
//  Created by 王宁 on 2019/3/8.
//  Copyright © 2019年 王宁. All rights reserved.
//

#import <Foundation/Foundation.h>
#import "OrderModel.h"
#import "JingdongOrderIterator.h"
NS_ASSUME_NONNULL_BEGIN

@interface JingdongOrderAggregrate : NSObject
@property(nonatomic,strong)NSMutableArray<OrderModel*>*set;
- (id<IteratorProtocol>)iterator;
@end

NS_ASSUME_NONNULL_END

//
//  JingdongOrderAggregrate.m
//  Andy_20190308_iterator
//
//  Created by 王宁 on 2019/3/8.
//  Copyright © 2019年 王宁. All rights reserved.
//

#import "JingdongOrderAggregrate.h"

@implementation JingdongOrderAggregrate
- (instancetype)init
{
    self = [super init];
    if (self) {
        self.set=[[NSMutableSet alloc]init];
        
        [self.set addObject:[[OrderModel alloc]initWithorderId:@"1" orderName:@"aaa" orderPrice:@"2222" orderDetail:@"dddd"]];
        [self.set addObject:[[OrderModel alloc]initWithorderId:@"2" orderName:@"bbb" orderPrice:@"2222" orderDetail:@"dddd"]];
        [self.set addObject:[[OrderModel alloc]initWithorderId:@"3" orderName:@"ccc" orderPrice:@"2222" orderDetail:@"dddd"]];
        
        
    }
    return self;
}

- (id<IteratorProtocol>)iterator
{
    return  [[JingdongOrderIterator alloc]initWIthSet:self.set];
}
@end

具体迭代器

//
//  JingdongOrderIterator.h
//  Andy_20190308_iterator
//
//  Created by 王宁 on 2019/3/8.
//  Copyright © 2019年 王宁. All rights reserved.
//

#import <Foundation/Foundation.h>
#import "OrderIterator.h"
#import "OrderModel.h"
NS_ASSUME_NONNULL_BEGIN

@interface JingdongOrderIterator : OrderIterator
@property(nonatomic,strong) NSEnumerator<OrderModel *> *iterator;

- (instancetype)initWIthSet:(NSMutableArray<OrderModel*>*)set;
@end

NS_ASSUME_NONNULL_END

//
//  JingdongOrderIterator.m
//  Andy_20190308_iterator
//
//  Created by 王宁 on 2019/3/8.
//  Copyright © 2019年 王宁. All rights reserved.
//

#import "JingdongOrderIterator.h"

@implementation JingdongOrderIterator
- (instancetype)initWIthSet:(NSMutableArray<OrderModel*>*)set
{
    self = [super initWithObj:set];
    if (self) {
        self.iterator=set.objectEnumerator;
    }
    return self;
}


- (OrderModel *)next
{
    if([self hasNext])
    {
        OrderModel* result = self.iterator.nextObject;
        Index += 1;
        return result;
        
    }
    return nil;
}

- (BOOL)hasNext
{
    NSMutableArray *set=(NSMutableArray<OrderModel*>*)self.obj;
    return Index!=set.count;
}
@end

实现

//
//  main.m
//  Andy_20190308_iterator
//
//  Created by 王宁 on 2019/3/8.
//  Copyright © 2019年 王宁. All rights reserved.
//

#import <UIKit/UIKit.h>
#import "AppDelegate.h"
#import "TianmaoOrderAggregrate.h"
#import "JingdongOrderAggregrate.h"
//let aggregrate = TianmaoOrderAggregrate()
//let iterator = aggregrate.iterator()
//while iterator.hasNext(){
//    let result = iterator.next()
//    //得到这个元素(打印可能为nil，需要指定一个默认值->语法)
//    print("orderId:\(String(describing: result?.orderId))")
//    print("orderName:\(String(describing: result?.orderName))")
//}
int main(int argc, char * argv[]) {
    @autoreleasepool {
        //这里可以将容器抽象出来，将容器实现协议来弄
        JingdongOrderAggregrate *tianmao=[[JingdongOrderAggregrate alloc]init];
        id<IteratorProtocol> iterator=[tianmao iterator];
        while (iterator.hasNext) {
            OrderModel *ordermodel=iterator.next;
            NSLog(@"orderId:%@",ordermodel.orderId);
            NSLog(@"orderName:%@",ordermodel.orderName);
        }
        
        
    }
}