黑马程序员 --- NSDictionary和NSMutableDictionary的用法

NSDictionary和NSMutableDictionary的用法

NSDictionary 翻译过来就是“字典”，键值对；日常生活中，“字典”的作用：通过一个拼音或者汉字，就能找到对应详细的解释。

NSDictionary 的作用类似：通过一个key（键），就能找到对应的value（值）；

NSDictionary是不可变的，一旦初始化完毕后，里面的内容就无法修改.

NSDictionary的创建：

NSDictionary *dict1 = [NSDictionary dictionary]; //空字典//含有多对键值对的数据NSDictionary *dict2 = [NSDictionary dictionaryWithObjectsAndKeys:@"value1",@"k1",@"value2",@"k2",nil];//将一个字典赋值给另一个字典NSDictionary *dict3 = [NSDictionary dictionaryWithDictionary:dict2];//只含有一对键值对的字典NSDictionary *dict4 = [NSdictionary ditctionaryWithObject:@"value1" forKey:@"k1"];//快速创建字典：NSDictionary *dict5 = @{@”k1”:@”value1”,@”k2”:@”value2”};

访问其中value 

NSString *str = [dict objectForKey :@”k1];NSString *str2 = dict[@”k2”];

读文件：

NSString *path = [[NSBundle mainBundle] pathForResource:@"dict.plist" ofType:nil];   //文件路径NSDictionary *dict2 = [NSDictionary dictionaryWithContentsOfFile:path];

写文件：

BOOL flag = [dict writeToFile:@”/users/zzf/Desktop/dict.plist” atomically:YES];if(flag){NSLog(@”写入成功”);}

字典遍历：

第一种方法：

NSDictionary *dict5 = @{@”k1”:@”value1”,@”k2”:@”value2”};for(NSString *str in dict5){<span style="white-space:pre"></span>NSLog(@"%@ --> %@",str,dict5[str]);}

第二种方法:

NSDictionary *dict5 = @{@”k1”:@”value1”,@”k2”:@”value2”};[dict5 enumerateKeysAndObjectsUsingBlock:^(id key ,id obj ,BOOL *stop){        NSLog(@"%@ --> %@",key,obj);}];

NSMutableDictionary是NSDictionary的子类；NSMutableDictionary是可变字典，随时可以往里面添加、更改和删除元素。

动态字典的创建:

NSMutableDictionary *dict1 = [NSMutableDictionary dictionary]; //空字典//含有多对键值对的数据NSMutableDictionary *dict2 = [NSMutableDictionary dictionaryWithObjectsAndKeys:@"value1",@"k1",@"value2",@"k2",nil];//将一个字典赋值给另一个字典NSMutableDictionary *dict3 = [NSMutableDictionary dictionaryWithDictionary:dict2];//创建一对键值对NSMutableDictionary *dict4 = [NSMutableDictionary ditctionaryWithObject:@"value1" forKey:@"k1"];

添加键值对：

[dict setValue:@”lisi” forKey:@”ls”];

 

删除键值对：

[dict removeObjectForKey:@”ls”];[dict removeAllObjects];

修改键值对：

[dict setObject:@”zhaosi” forKey:@”ls”];Dict[@”ls”] = @”zhaosi”;

查找键值对：

NSArray * arr = [dict allKeys];if(arr containsObject:@”ls”]){<span style="white-space:pre"></span>NSLog(@“含有这个键值对”);}

NSDictionary 的创建的类方法:

+(id)dictionary;

+(id)dictionaryWithContentsOfFile:(NSString *)path;

+(id)dictionaryWithContentsOfURL:(NSString *)path;

+(id)dictionaryWithDictionary:(NSDictionary*)dict;

+(id)dictionaryWithObjectsAndKeys;

+(id)ditctionaryWithObject:(id)data forKey:(id)key;