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;