Objective-C字典初识

字典中存放的是键值对   可通过键取得值

1.创建不可变字典

1 //         1  f(1)
2         NSDictionary * dic = [[NSDictionary alloc] initWithObjectsAndKeys:@"one",@"1",@"two",@"2",@"three",@"3", nil];
3         NSLog(@"%@",dic);
4
5         // 2 快速创建字典
6         NSDictionary * dic2 = @{@"1":@"one",@"2":@"two",@"3":@"three"};
7         NSLog(@"%@",dic2);

2.字典中的元素个数

1 NSUInteger count = [dic2 count];

2 NSLog(@"%lu",count);

3.字典中可以存放数组

1         NSArray * arr = @[@"one",@"two",@"three"];
2         NSDictionary * dic3 = @{@"1":@"one",@"array":arr,@"2":@"two"};
3         NSLog(@"%@",dic3);

4.字典中取值

1         // 5 从字典中取值
2         NSArray * arr2 = [dic3 objectForKey:@"array"];
3         NSLog(@"%@",arr2);
4         // 快速取法
5         NSArray * arr3 = dic3[@"array"];
6         NSLog(@"%@",arr3);  

5.可变字典

　　5.1 可变字典的创建

1  // 创建
2         NSMutableDictionary * muDic = [[NSMutableDictionary alloc] initWithObjectsAndKeys:@"one",@"1",@"two",@"2", nil];
3
4         NSDictionary * dic = @{@"1":@"one",@"2":@"two"};
5
6         NSMutableDictionary * muDic2 = [[NSMutableDictionary alloc] initWithDictionary:dic];
7
8         NSLog(@"%@",muDic2);

　　5.2 向字典中添加元素

1         [muDic2 setObject:@"three" forKey:@"3"];
2         NSLog(@"%@",muDic2);

　　5.3 重置字典（set方法）

1         [muDic2 setDictionary:@{@"a":@"one",@"b":@"two"}];
2         NSLog(@"%@",muDic2);

　　5.4 删除元素

　　　　删除key对应的键值对

1 [muDic2 removeObjectForKey:@"a"];

2 NSLog(@"%@",muDic2);

　　　　删除全部

1

2 [muDic2 removeAllObjects];

3 NSLog(@"%@",muDic2);

　　5.5打印字典中的元素

1         NSArray * arr = [muDic2 allKeys];
2         // arr存储字典中所有的key
3         NSLog(@"%@",arr);
4         // 用快速枚举的方式打印字典muDic中的值
5         for (NSString * str in arr) {
6 //            NSLog(@"%@",[muDic2 objectForKey:str]);
7             NSLog(@"%@",muDic2[str]);
8         }

扩展

- (BOOL)isKindOfClass:(Class)aClass;

判断是否是某种类型

example

[obj isKindOfClass:[NSString class]];

判断obj是否是NSString类型 返回值为BOOL类型