不可變字典
一 創(chuàng)建字典對象
1） NSDictionary *dic1 = [[NSDictionary alloc] initWithObjectsAndKeys:@100,@"老 談",@"two",@"2",@"three",@"3", nil];

2） NSDictionary *dic2 = [[NSDictionary alloc] initWithObjects:@[@"qf",@"1603"]          forKeys:@[@"name",@"className"]];

3）NSDictionary *dic3 = @{@"1":@"one",@"2":@"two",@"3":@"three"};     【重點(diǎn)】

二 字典的常用方法
1）通過key取得對應(yīng)的value 【重點(diǎn)】
NSNumber *nm = [dic1 objectForKey:@"老談"];
int a = [nm intValue];
NSLog(@"a = %d",a);
//方法嵌套使用
NSLog(@"%d",[[dic1 objectForKey:@"老談"] intValue]);

    新語法 NSString *str = dic3[@"3"];    //取出鍵為3的值                 【新語法】

2）返回所有的key
    NSArray *keys = [dic3 allKeys];
    
    
3）返回所有的value
    NSArray *values = [dic3 allValues];

4）返回鍵值對的個數(shù)
     NSLog(@"count = %ld", dic3.count);
5）字典的遍歷                                       【***重中之重***】
    //快速枚舉遍歷字典
    //in的右邊所遍歷的那個字典對象
    //in的左邊字典中key的類型            key要有意義，所以一般都用字符串來寫
    for (NSString *keyStr in dic1) {
        NSLog(@"key = %@ ---- value = %@",keyStr,dic1[keyStr]);
    }

可變字典
一 創(chuàng)建可變字典
1)創(chuàng)建一個空的可變字典 【***常見】
NSMutableDictionary *mDict1 = [[NSMutableDictionary alloc] init];
NSMutableDictionary *mDict2 = [NSMutableDictionary dictionary];

2)創(chuàng)建帶多個鍵值對的可變字典

NSMutableDictionary *mDict3 = [[NSMutableDictionary allo] initWithObjectsAndKeys:, nil];
NSMutableDictionary *mDict4 = [NSMutableDictionary dictionaryWithObjectsAndKeys:, nil];

3)把一個不可變字典轉(zhuǎn)換成可變字典                                 【***常見】
    NSDictionary *dict = @{@"1":@"one",@"2":@"two",@"3":@"three"};

NSMutableDictionary *mDict5 = [[NSMutableDictionary alloc] initWithDictionary:dict];
NSMutableDictionary *mDict6 = [NSMutableDictionary dictionaryWithDictionary:dict];

二 添加鍵值對
[mDict6 setObject:@"four" forKey:@"4"];
NSLog(@"mDict6 = %@", mDict6);

    [mDict6 setObject:@"A" forKey:@"1"];
    NSLog(@"mDict6 = %@", mDict6);

三 刪除鍵值對
//1.根據(jù)key刪除對應(yīng)的鍵值對
[mDict6 removeObjectForKey:@"2"];
NSLog(@"mDict6 = %@", mDict6);

    //2.刪除多個鍵值對
    [mDict6 removeObjectsForKeys:@[@"1",@"4"]];         //一次刪除多個用數(shù)組
    NSLog(@"mDict6 = %@", mDict6);
    
    
    //3.刪除所有的鍵值對
    [mDict6 removeAllObjects];
    NSLog(@"mDict6 = %@", mDict6);

四 重置鍵值對
//1.重置鍵值對
[mDict6 setDictionary:@{@"1":@"A",@"2":@"B",@"3":@"C"}];
NSLog(@"mDict6 = %@", mDict6);