OC语言基础之NSDictionary

1.NSDictionary字典的创建

// key value
    // key -==> value
    NSDictionary *dict = [NSDictionary dictionaryWithObject:@"v" forKey:@"key"];

    NSArray *keys = [NSArray arrayWithObjects:@"k1", @"k2", nil];
    NSArray *values = [NSArray arrayWithObjects:@"v1", @"v2", nil];
    NSDictionary *dict1 = [NSDictionary dictionaryWithObjects:values
                                                      forKeys:keys];
    NSDictionary *dict2 = [NSDictionary dictionaryWithObjectsAndKeys:@"v", @"key",
                           @"v1", @"key1",
                           nil];
    NSLog(@"%@", dict2);


    //    BOOL isSuccess = [dict writeToFile:@"/Users/apple/Desktop/1.txt"
    //           atomically:YES];
    //    if (isSuccess) {
    //        NSLog(@"成功");
    //    }else{
    //        NSLog(@"写入失败");
    //    }

    NSDictionary *dict3 = [NSDictionary dictionaryWithContentsOfFile:@"/Users/apple/Desktop/1.txt"];
    NSLog(@"%@", dict3);

字典的遍历

NSDictionary *pDict = [NSDictionary dictionaryWithObjectsAndKeys:@"abc", @"name",
                          @"11", @"age",
                          @"男", @"gender",
                          nil];
   //    NSArray *keys = [pDict allKeys];
   //    for (int i = 0; i<[pDict count]; i++) {
   //        NSString *key = [keys objectAtIndex:i];
   //        NSString *value = [pDict objectForKey:key];
   //        NSLog(@"%@: value= %@", key, value);
   //    }

   //    for (id key in pDict) {
   //        NSLog(@"%@", key);
   //    }
   //

   [pDict enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
       NSLog(@"%@", key);

       // 修改stop指向内存的值
       *stop = YES;
   }];

2.可变字典

    NSMutableDictionary *dictM = [NSMutableDictionary dictionaryWithObjectsAndKeys:@"v", @"key",
                                  nil];
    [dictM setObject:@"1" forKey:@"key"];
    NSLog(@"%@", dictM);

3.具体使用的例子

// 名字
    // 年龄
    // 性别
    NSDictionary *pDict = [NSDictionary dictionaryWithObjectsAndKeys:
                           @"11", @"age",
                           @"abc", @"name",
                           @"男", @"gender",
                           nil];


    //    NSMutableArray *array = [NSMutableArray array];
    //    [array addObject:pDict];

    id name = [pDict objectForKey:@"name"];
    NSLog(@"%@", name);

4.各常用类对比

/*
 集合
 1.NSArrayNSMutableArray
 * 有序
 * 快速创建（不可变）：@[obj1, obj2, obj3]
 * 快速访问元素：数组名[i]

 2.NSSetNSMutableSet
 * 无序

 3.NSDictionaryNSMutableDictionary
 * 无序
 * 快速创建（不可变）：@{key1 : value1,  key2 : value2}
 * 快速访问元素：字典名[key]
 */

例子

/*
    字典：

    key ----> value
    索引 ----> 文字内容

    里面存储的东西都是键值对


    */

   // NSDictionary *dict = [NSDictionary dictionaryWithObject:@"jack" forKey:@"name"];


   // NSArray *keys = @[@"name", @"address"];
   // NSArray *objects = @[@"jack", @"北京"];

   // NSDictionary *dict = [NSDictionary dictionaryWithObjects:objects forKeys:keys];


   /*
    NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:
    @"jack", @"name",
    @"北京", @"address",
    @"32423434", @"qq", nil];*/


   NSDictionary *dict = @{@"name" : @"jack", @"address" : @"北京"};

   // id obj = [dict objectForKey:@"name"];

   id obj = dict[@"name"];

   NSLog(@"%@", obj);



   // 返回的是键值对的个数
   NSLog(@"%ld", dict.count);