一、NSDictionary基本概念

• NSDictionary的作用類似：通過一個key，就能找到對應的Value

• NSDictionary是一個不可變的，一旦初始化后，就無法修改

二、NSDictionary的創(chuàng)建

• 方法一：
• 創(chuàng)建一個dictionaryWithObject
• 創(chuàng)建多個dictionaryWithObjects

NSDictionary *dict = [NSDictionary dictionaryWithObject:@"lm" forKey:@"name"];
NSString *name = [dict objectForKey:@"name"];

• 方法二：簡單方法
• NSDictionary *dict = @{key1:value1,key2:value2};

NSDictionary *dict = @{@"lm":@"name",@"25":@"age",@"160":@"height"};

三、如何獲取

• 方法一：objectForKey

NSString *name = [dict objectForKey:@"name"];

• 方法二：NSLog(@"%@", dict[@"name"]);

四、字典的遍歷

• 如何獲取字典中key和value的個數(shù),

• 在字典中key稱之為鍵, value稱之為值

• NSLog(@"count = %lu", [dict count]);

• 方法一：for循環(huán)【不用】

 for (int i = 0; i < dict.count; ++i) {
        // 獲取字典中所有的key
        NSArray *keys = [dict allKeys];
        // 取出當前位置對應的key
//        NSLog(@"%@", keys[i]);
        NSString *key = keys[i];
        NSString *value = dict[key];
        NSLog(@"key = %@, value = %@", key, value);
    }

• 方法二：forin遍歷字典【不用】

for (NSString *key in dict) {
//        NSLog(@"%@", key);
        NSString *value = dict[key];
        NSLog(@"key = %@, value = %@", key, value);
    }

• 方法三：迭代器遍歷enumerateKeysAndObjectsUsingBlock

    NSDictionary *dict = @{@"lm":@"name",@"25":@"age",@"160":@"height"};
    [dict enumerateKeysAndObjectsUsingBlock:^(id  _Nonnull key, id  _Nonnull obj, BOOL * _Nonnull stop) {
        NSLog(@"obj:%@, key:%@", obj, key);
    }];

五、字典文件讀寫

• 字典讀取writeToFile
• 字典寫入dictionaryWithContentsOfFile

[dict writeToFile:@"/Users/jeffrey/Desktop/php.plist" atomically:YES];
NSDictionary * dict = [NSDictionary dictionaryWithContentsOfFile:@"/Users/jeffrey/Desktop/php.plist"];

六、NSMutableDictionary

• 1.創(chuàng)建一個空的字典

NSMutableDictionary *dictM = [NSMutableDictionary  dictionary];
```objc
- 2.如何添加
```objc
[dictM setObject:@"lm" forKey:@"name"];
// 會將傳入字典中所有的鍵值對取出來添加到dictM中
    [dictM setValuesForKeysWithDictionary:@{@"age":@"30", @"height":@"1.75"}]
```objc
- 3.如何獲取
```objc
NSLog(@"%@", dictM[@"lm"]);

• 4.如何刪除

[dictM removeObjectForKey:@"lm"];

• 5.如何修改
  • 如果利用setObject方法給同名的key賦值, 那么新值會覆蓋舊值

[dictM setObject:@"88" forKey:@"age"];
     dictM[@"age"] = @"88";