学习链接：https://www.cnblogs.com/-boy/archive/2004/01/13/4096453.html

//
//  learn_dic.m
//  learn_KVC
//
//  Created by 蔡佳明 on 2020/10/15.
//

#import <Foundation/Foundation.h>
int main()
{
    //创建字典 必须初始化 并且创建之后不能再变了
    
    // 没初始化 没意义
    NSDictionary *dic=[NSDictionary dictionary];
    
    //创建只有一个键值对的字典
    NSDictionary *dic1=[NSDictionary dictionaryWithObject:@"yaoming" forKey:@"ym"];
    
    //创建多个键值对字典
    NSDictionary *dic2=[NSDictionary dictionaryWithObjectsAndKeys:@"liuxiang",@"lx",@"jiaming",@"jm", nil];
    
    //快速创建方法
    NSDictionary *dic3=@{@"ym":@"yaoming",@"lx":@"liuxiang"};
    
    //字典访问
    
    //返回字典中键值个数
    NSUInteger len=dic3.count;
    NSLog(@"键值个数为：%lu",len);
    
    //根据键求值
    //方式1
    id str=[dic3 objectForKey:@"lx"];
    //方式2
    str=dic3[@"lx"];
    NSLog(@"str=%@",str);
    
    //字典的遍历
    //for循环
    id key=[dic3 allKeys];
    for(int i=0;i<dic3.count;i++)
    {
        str=dic3[key[i]];
        NSLog(@"%@:%@",key[i],str);
    }
    
    //for in遍历
    for(NSString *key in dic3)
    {
        str=dic3[key];
        NSLog(@"%@:%@",key,str);
    }
    
    //下面说一下可变的的字典
    //创建一个可变的空字典
    NSMutableDictionary *dicM = [NSMutableDictionary dictionary];
    [dicM setObject:@"zhangsan" forKey:@"zs"];
    [dicM setObject:@"lisi" forKey:@"ls"];
    
    
    for(NSString *key in dicM)
    {
        str=dicM[key];
        NSLog(@"%@:%@",key,str);
    }
    
    //删除指定的键值对
    [dicM removeObjectForKey:@"zs"];
    
    for(NSString *key in dicM)
    {
        str=dicM[key];
        NSLog(@"%@:%@",key,str);
    }
    //删除字典中所有的内容
    [dicM removeAllObjects];
    
    return 0;
}