//创建字典
        //注意:
        //1，元素个数是偶数
        //2，每两个元素是一个键值对
        //3，值在前，键在后
        NSDictionary *dic = [[NSDictionary alloc] initWithObjectsAndKeys:@"huang",@"name",@"30",@"age", nil];
        NSLog(@"%@",dic);
        
        //用一个字典来创建另外一个字典
        NSDictionary *dic2 = [[NSDictionary alloc] initWithDictionary:dic];
        
        //注意:
        //1,value和key的个数要相同
        //2,values和keys里面的元素的先后顺序要对应
        NSDictionary *dic3 = [[NSDictionary alloc] initWithObjects:[NSArray arrayWithObjects:@"huang",@"30", nil] forKeys:[NSArray arrayWithObjects:@"name",@"age", nil]];
        NSLog(@"%@",dic3);
        
        //创建数组的新方式
        NSArray *arr = @[@"1",@"2",@"3"];
        NSDictionary *dic4 = [NSDictionary dictionaryWithObjectsAndKeys:@"30",@"age",@"huang",@"name", nil];
        NSDictionary *dic5 = [NSDictionary dictionaryWithDictionary:dic4];
        NSDictionary *dic6 = [NSDictionary dictionaryWithObjects:@[@"huang",@"30"] forKeys:@[@"name",@"age"]];
        //创建字典的新方式
        NSDictionary *dic7 = @{@"name": @"huang",@"age":@"30"};

        //字典的常用操作
        NSInteger count = [dic7 count];
        NSLog(@"%ld",count);
        
        //根据键去获取值
        NSString *str = [dic7 valueForKey:@"name"];
        NSLog(@"%@",str);
        
        //获取所有的key
        NSArray *allKeys = [dic7 allKeys];
        NSLog(@"%@",allKeys);
        
        //获取所有的value
        NSArray *allValues = [dic7 allValues];
        
        //获取一个value对应的key
        NSDictionary *dic8 = @{@"name":@"huang",@"age":@"15",@"score":@"15"};
        NSArray *arr1 = [dic8 allKeysForObject:@"15"];
        NSLog(@"%@",arr1);
        
        NSDictionary *dic9 = @{@"dic8":dic8,@"dic7":dic7};
        NSLog(@"%@",dic9);
        
        //数组与字典的嵌套
        NSArray *array1 = @[@"1",@"2",@"3"];
        NSDictionary *dictionary1 = @{@"name":@"xiaoming",@"age":@"10"};
        
        NSDictionary *dictionary2 = @{@"array":array1,@"dictionary":dictionary1};
        NSLog(@"%@",dictionary2);
        
        NSArray *array2 = @[array1,dictionary1];
        NSLog(@"%@",array2);
        
        //字典的遍历
        NSDictionary *dictionary3 = @{@"name":@"huang",@"age":@"30",@"number":@"30"};
        NSArray *allKeys1 = [dictionary3 allKeys];
        for(NSString *key in allKeys1)
        {
            NSString *str = [dictionary3 objectForKey:key];
            NSLog(@"%@=%@",key,str);
        }

        NSDictionary *dic = @{@"name":@"xiaoming",@"age":@"10"};
        NSDictionary *dic1 = @{@"age":@"15",@"score":@"30"};
        
        NSMutableDictionary *muDic = [[NSMutableDictionary alloc] init];
        
        //从一个字典内添加元素到可变字典
        //注意:
        //当dic与可变字典有相同的key时,不添加这个key，但是会将key对应的value覆盖。
        [muDic addEntriesFromDictionary:dic];
        NSLog(@"%@",muDic);
        [muDic addEntriesFromDictionary:dic1];
        NSLog(@"%@",muDic);
        
        //添加一个元素
        //注意:
        //1，setObject:forKey:  当key不存在时就是添加元素，当key存在时就是修改元素值
        [muDic setObject:@"mingming" forKey:@"nickname"];
        [muDic setObject:@"xiaohua" forKey:@"name"];
        NSLog(@"%@",muDic);
        
        //删除一个元素
        [muDic removeObjectForKey:@"name"];
        NSLog(@"%@",muDic);
        
        //删除一个keys数组里面对应的所有元素
        [muDic removeObjectsForKeys:@[@"nickname",@"aaa"]];
        NSLog(@"%@",muDic);
        
        //删除字典内的所有元素
        [muDic removeAllObjects];
        NSLog(@"%@",muDic);
        
        //修改字典
        [muDic setDictionary:dic];
        NSLog(@"%@",muDic);