更新时间:2022-05-08 00:17:11
快速枚举,这个是苹果推荐的枚举方法。它允许把集合对象的枚举直接用作for循环的一部分,无需使用其他枚举器对象,而且比传统的基于索引的for循环效率更高,形如:
NSArray *arr = @[@"zhangsan",@"lisi",@"wangwu"];
for(NSString *item in arr)
{
NSLog(@"%@",item);
}
该例子定义了一个集合Set和一个迭代器ConcreteIterator。然后通过迭代器来输出集合Set对象的元素。
ConcreteSet.h
//
// ConcreteSet.h
// IterationDemo
//
// Created by zhanggui on 15/8/8.
// Copyright (c) 2015年 zhanggui. All rights reserved.
//
#import <Foundation/Foundation.h>
@interface ConcreteSet : NSObject
{
NSMutableArray *items;
}
-(NSInteger)getCount;
-(id)getItemFromIndex:(NSInteger)index;
-(void)insertItem:(id)item;
@end
ConcreteSet.m
//
// ConcreteSet.m
// IterationDemo
//
// Created by zhanggui on 15/8/8.
// Copyright (c) 2015年 zhanggui. All rights reserved.
//
#import "ConcreteSet.h"
#import "ConcreteIterator.h"
@implementation ConcreteSet
-(id)init
{
self = [super init];
if (self) {
items = [NSMutableArray new];
}
return self;
}
-(NSInteger)getCount
{
return [items count];
}
-(id)getItemFromIndex:(NSInteger)index
{
return [items objectAtIndex:index];
}
-(ConcreteIterator *)createiterator
{
return [ConcreteIterator new];
}
-(void)insertItem:(id)item
{
[items addObject:item];
}
@end
Concreteiterator.h
//
// ConcreteIterator.h
// IterationDemo
//
// Created by zhanggui on 15/8/8.
// Copyright (c) 2015年 zhanggui. All rights reserved.
//
#import <Foundation/Foundation.h>
@class ConcreteSet;
@interface ConcreteIterator : NSObject
{
ConcreteSet *mySet;
int current;
}
-(id)FirstItem;
-(id)nextItem;
-(BOOL)isFinish;
-(id)currentItem;
-(id)initWithConcreteSet:(ConcreteSet *)concrete;
@end
Concreteiterator.m
//
// ConcreteIterator.m
// IterationDemo
//
// Created by zhanggui on 15/8/8.
// Copyright (c) 2015年 zhanggui. All rights reserved.
//
#import "ConcreteIterator.h"
#import "ConcreteSet.h"
@implementation ConcreteIterator
-(id)initWithConcreteSet:(ConcreteSet *)concrete
{
self = [super init];
if (self) {
mySet = concrete;
}
return self;
}
-(id)FirstItem
{
return [mySet getItemFromIndex:0];
}
-(id)nextItem
{
current ++;
if (current<[mySet getCount]) {
return [mySet getItemFromIndex:current];
}else
{
return nil;
}
}
-(BOOL)isFinish
{
return current>=[mySet getCount] ? YES : NO;
}
-(id)currentItem
{
return [mySet getItemFromIndex:current];
}
@end
然后在ViewController中测试
//
// ViewController.m
// IterationDemo
//
// Created by zhanggui on 15/8/8.
// Copyright (c) 2015年 zhanggui. All rights reserved.
//
#import "ViewController.h"
#import "ConcreteIterator.h"
#import "ConcreteSet.h"
@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// NSArray *arr = @[@"apple",@"banana",@"orange"];
//
// for(NSString *item in arr)
// {
// NSLog(@"%@",item);
// }
ConcreteSet *set = [[ConcreteSet alloc] init];
[set insertItem:@"apple"];
[set insertItem:@"banana"];
[set insertItem:@"orange"];
NSLog(@"Count is :%ld",(long)[set getCount]);
ConcreteIterator *iterator = [[ConcreteIterator alloc] initWithConcreteSet:set];
while (![iterator isFinish]) {
NSLog(@"%@",[iterator currentItem]);
[iterator nextItem];
}
}
@end
用自己定义的迭代器去输出元素和用苹果枚举效果类似。苹果推荐使用类似与viewDidLoad方法中的for循环来输出集合元素。