又到晚上了，继续码代码。

正在此时，老爸一个电话”海阔凭鱼跃，天高任鸟飞“,老爸不在为老问题烦我了。

自由了，突然感觉压力好大啊。

将来混的太惨，可咋办啊～

第1个例子是，不可变集合。

Set集合，概念是通用的，无非是和Java中的java.util.Set语法不一致，方法的个数不一致罢了。

集合的核心特征，就是元素不会重复，是否重复根据元素的hashCode和equals方法来定。

代码

//
//  main.m
//  NSSetTest
//
//  Created by fansunion on 15/12/3.
//  Copyright (c) 2015年 demo. All rights reserved.
//#import <Foundation/Foundation.h>
//定义一个函数，可以把Array或者NSSet集合转换为字符串
NSString*  NSCollectionToString(id collection){NSMutableString* str = [NSMutableString stringWithString:@"["];//使用for-each循环语法，遍历集合for(id obj in collection){[str appendString:[obj description]];[str appendString:@", "];}//获取字符串长度，去掉最后2个多余的字符NSUInteger length = [str length];[str deleteCharactersInRange:NSMakeRange(length-2, 2)];[str appendString:@"]"];return str;
}//NSSet是不可变集合，可变集合是NSMutableSet。
//与NSArray，NSMutableArray一个鸟样
int main(int argc, const char * argv[]) {@autoreleasepool {//构造4个元素的集合，其中2个是重复的NSSet* set1 = [NSSet setWithObjects:@"A", @"B",@"C",@"B",nil];NSLog(@"The set1 count :%ld",[set1 count]);NSLog(@"The set1 :%@",NSCollectionToString(set1));//set1是不可变集合NSSet* set2 =[set1 setByAddingObject:@"D"];NSLog(@"The new set1 :%@",NSCollectionToString(set1));NSLog(@"The set2 :%@",NSCollectionToString(set1));BOOL isSubSet =[set1 isSubsetOfSet:set2];NSLog(@"The set1 is subSet of set2:%d",isSubSet);BOOL have = [set1 containsObject:@"C"];NSLog(@"The set1 has C:%d",have);}return 0;
}

运行结果

2015-12-03 20:16:52.049 NSSetTest[5903:419290] The set1 count :3

2015-12-03 20:16:52.050 NSSetTest[5903:419290] The set1 :[A, B, C]

2015-12-03 20:16:52.050 NSSetTest[5903:419290] The new set1 :[A, B, C]

2015-12-03 20:16:52.051 NSSetTest[5903:419290] The set2 :[A, B, C]

2015-12-03 20:16:52.051 NSSetTest[5903:419290] The set1 is subSet of set2:1

2015-12-03 20:16:52.051 NSSetTest[5903:419290] The set1 has C:1

Program ended with exit code: 0

照目前这个学习进度，2017年之前，初步掌握Object-C和iOS，是没啥问题的。