objective-c基础语法之字典NSDIctionary、NSMutableDictionary

//创建一个空字典
NSDictionary *dic = [[NSDictionary alloc]init];
//根据本地文件创建一个字典
NSDictionary *dic = [[NSDictionary alloc]initWithContentsOfFile:(NSString *)];
//根据网址URL创建一个字典
NSDictionary *dic = [[NSDictionary alloc]initWithContentsOfURL:(NSURL *)];
//根据已知字典创建一个新的字典
NSDictionary *dic = [[NSDictionary alloc]initWithDictionary:(NSDictionary *)];

//根据值的集合数组与键的集合数组创建一个字典
NSDictionary *dic = [[NSDictionary alloc]initWithObjects:(NSArray *) forKeys:(NSArray *)];
//使用如下：
NSArray *arr_values = [[NSArray alloc]initWithObjects:@"Mary","female", nil];
    NSArray *arr_keys = [[NSArray alloc]initWithObjects:@"name","sex", nil];
    NSDictionary *dic = [[NSDictionary alloc]initWithObjects:arr_values forKeys:arr_keys];

//创建容量初始为多少的字典
NSMutableDictionary *mutable_dic = [[NSMutableDictionary alloc]initWithCapacity:(NSUInteger)];
//使用如下：

NSMutableDictionary *mutable_dic = [[NSMutableDictionary alloc]initWithCapacity:0];

//读取字典中的值
[mutable_dic objectForKey:(id)];
//读取键为@"name"对应的值
[mutable_dic objectForKey:@"name"];

//获取字典的长度
[mutable_dic count];

//获取字典中所有的键值
[mutable_dic allKeys];