分类：NSDictionary（不可变数据字典）和NSMutableDictionary（可变数据字典）

组成：

 1    //1、用一个或多个键值对初始化一个字典对象: 以值,建,值,键,...,nil的顺序
 2     NSDictionary *dict01=[[NSDictionary alloc] initWithObjectsAndKeys:@"key0",@"value0",@"key1",@"value1",@"key2",@"value2", nil];
 3     NSLog(@"dict01:%@",dict01);
 4     NSDictionary *dict1=[NSDictionary dictionaryWithObjectsAndKeys:@123,@"key0",@456,@"key1",@678,@"key2", nil];
 5     NSLog(@"dict1:%@",dict1);
 6     //2、用两个数组初始化一个字典，一个key数组，一个value数组，两个数组大小必须相等，否则Crash
 7     NSArray *keyArray=@[@"name0",@"name1",@"name2"];
 8     NSArray *valueArray=@[@"hong",@"wang",@"zhao"];
 9     NSDictionary *dict02=[[NSDictionary alloc] initWithObjects:keyArray forKeys:valueArray];
10     NSDictionary *dict2=[NSDictionary dictionaryWithObjects:valueArray forKeys:keyArray];
11     NSLog(@"dict02:%@",dict02);
12     NSLog(@"dict2:%@",dict2);
13     
14     //3、用一个数据字典初始化另一个数据字典
15     NSDictionary *dict03=[[NSDictionary alloc] initWithDictionary:dict1];
16     NSDictionary *dict3=[NSDictionary dictionaryWithDictionary:dict1];
17     NSLog(@"dict03:%@",dict03);
18     NSLog(@"dict3:%@",dict3);

（2）字典对象的创建和保存-文件

    //1、保存字典对象内容到文件
    [dict3 writeToFile:@"/Users/apple/Desktop/tesk.txt" atomically:YES];
    
    //2、从之前保存的文件读取数据到字典对象
    NSDictionary *dict4=[NSDictionary dictionaryWithContentsOfFile:@"/Users/apple/Desktop/tesk.txt"];
    NSLog(@"dict4:%@",dict4);

(3)字典对象元素的访问

 1     //1、分别获取字典的所有键、值
 2     NSArray *allkeys=[dict1 allKeys];
 3     NSLog(@"allkeys:%@",allkeys);
 4     NSArray *allvalues=[dict1 allValues];
 5     NSLog(@"allvalues:%@",allvalues);
 6     
 7     //2、通过指定的key取对应的value对象,没有这个key的话.返回nil
 8     NSNumber *num1 = [dict1 objectForKey:@"key1"];
 9     NSNumber *num2 = [dict1 objectForKey:@"key5"];
10     NSLog(@"%@",num1);
11     NSLog(@"%@",num2);
12     
13     //3、获取字典中键值对的个数
14     NSUInteger paircount=[dict2 count];
15     NSLog(@"%lu",paircount);

（4）字典的遍历

1     for (id key in dict1) {
2         id value=[dict1 objectForKey:key];
3         NSLog(@"%@=%@",key,value);
4     }

2015-04-07 21:17:53.933 NSDictionary[5465:226991] dict01:{
    value0 = key0;
    value1 = key1;
    value2 = key2;
}
2015-04-07 21:17:53.934 NSDictionary[5465:226991] dict1:{
    key0 = 123;
    key1 = 456;
    key2 = 678;
}
2015-04-07 21:17:53.934 NSDictionary[5465:226991] dict02:{
    hong = name0;
    wang = name1;
    zhao = name2;
}
2015-04-07 21:17:53.934 NSDictionary[5465:226991] dict2:{
    name0 = hong;
    name1 = wang;
    name2 = zhao;
}
2015-04-07 21:17:53.935 NSDictionary[5465:226991] dict03:{
    key0 = 123;
    key1 = 456;
    key2 = 678;
}
2015-04-07 21:17:53.935 NSDictionary[5465:226991] dict3:{
    key0 = 123;
    key1 = 456;
    key2 = 678;
}
2015-04-07 21:17:53.937 NSDictionary[5465:226991] dict4:{
    key0 = 123;
    key1 = 456;
    key2 = 678;
}
2015-04-07 21:17:53.938 NSDictionary[5465:226991] allkeys:(
    key1,
    key0,
    key2
)
2015-04-07 21:17:53.938 NSDictionary[5465:226991] allvalues:(
    456,
    123,
    678
)
2015-04-07 21:17:53.938 NSDictionary[5465:226991] num1:456
2015-04-07 21:17:53.938 NSDictionary[5465:226991] num2:(null)
2015-04-07 21:17:53.938 NSDictionary[5465:226991] 键值对个数：3
2015-04-07 21:17:53.938 NSDictionary[5465:226991] key1=456
2015-04-07 21:17:53.938 NSDictionary[5465:226991] key0=123
2015-04-07 21:17:53.938 NSDictionary[5465:226991] key2=678

二、可变数据字典

    //可变数据字典初始化

    NSMutableDictionary *mDict1=[NSMutableDictionary dictionaryWithObjectsAndKeys:@"aaa",@"name0",@"bbb",@"name1",@"ccc",@"name2", nil];

    NSLog(@"%@",mDict1);

    //1、加入元素到NSMutableDictionary中  （注意：当key值中存在要添加的键值对中的key值时，则添加，否则覆盖）

    [mDict1 setObject:@"ddd" forKey:@"name3"];

    [mDict1 setObject:@"eee" forKey:@"name1"];

    NSLog(@"add:  %@",mDict1);

    //2、查看 中所有元素个数：

    NSLog(@"%lu",mDict1.count);

    NSNumber *num3 =[mDict1 objectForKey:@"name1"];

    NSLog(@"%@",num3);

    NSNumber *num4 = [mDict1 objectForKey:@"name10"];

    NSLog(@"%@",num4);

    //3、添加其他NSMutableDictionary

    [mDict1 setValuesForKeysWithDictionary:dict1];

    NSLog(@"++++%@",mDict1);

    //4、根据key值删除

    [mDict1 removeObjectForKey:@"name1"];

    NSLog(@"---%@",mDict1);

    //5、删除所有

    [mDict1 removeAllObjects];

    NSLog(@"%@",mDict1);

2015-04-07 22:12:10.717 NSDictionary[5827:248322] add:  {
    name0 = aaa;
    name1 = eee;
    name2 = ccc;
    name3 = ddd;
}
2015-04-07 22:12:10.718 NSDictionary[5827:248322] 4
2015-04-07 22:12:10.718 NSDictionary[5827:248322] eee
2015-04-07 22:12:10.718 NSDictionary[5827:248322] (null)
2015-04-07 22:12:10.719 NSDictionary[5827:248322] ++++{
    key0 = 123;
    key1 = 456;
    key2 = 678;
    name0 = aaa;
    name1 = eee;
    name2 = ccc;
    name3 = ddd;
}
2015-04-07 22:12:10.719 NSDictionary[5827:248322] ---{
    key0 = 123;
    key1 = 456;
    key2 = 678;
    name0 = aaa;
    name2 = ccc;
    name3 = ddd;
}
2015-04-07 22:12:10.719 NSDictionary[5827:248322] {
}