//字典 键值对的数据结构
NSDictionary *dic1 = @{@"name":@"chicai", @"age":@"18"};
NSDictionary *dic2 = [[NSDictionary alloc] init];
NSArray *keys = [dic1 allKeys];
for(NSString * key in keys)
{
    NSLog(@"key=%@,val=%@", key, dic1[key]);
}

//可变字典
NSMutableDictionary *mdic = [[NSMutableDictionary alloc] initWithCapacity:20];
[mdic setObject:@"chifan" forKey:@"name"];
[mdic setObject:@"18" forKey:@"age"];
[mdic removeObjectForKey:@"age"];
for(NSString *key in [mdic allKeys])
{
    NSLog(@"key=%@,val=%@", key, mdic[key]);
}