Objective-C语法之NSDictionary和NSMutableDictionary

Java有Map，可以把数据以键值对的形式储存起来，取值的时候通过key就可以直接拿到对应的值，方便快捷。在Objective-C语言中，词典就是做这样的事情的，和NSArray一样，一个词典对象也能保存不同类型的值，词典也分别有不可变词典和可变的词典（NSDictionary与NSMutableDictionary），前者是线程安全的，后者不是 。



1、不可变词典NSDictionary的主要用法：

[NSDictionary dictionaryWithObjectsAndKeys:..] : 使用键值对直接创建词典对象，结尾必需使用nil标志结束。

[dictionary count]: 得到词典的键值对数量。

[dictionary keyEnumerator]: 将词典的所有key储存在NSEnumerator中，类似于Java语言中的迭代器

[dictionary objectEnumerator]: 将词典的所有value储存在NSEnumerator中

[dictionary objectForKey:key]: 通过传入key对象可以拿到当前key对应储存的值。

代码示例：

[cpp]
view plaincopyprint?

int main(int argc, const char * argv[])
{
@autoreleasepool {
NSDictionary *dictionary = [NSDictionary dictionaryWithObjectsAndKeys:@"25",@"age",@"张三",@"name",@"男",@"性别",nil];
NSLog(@"%lu", [dictionary count]);
NSEnumerator *enumeratorKey = [dictionary keyEnumerator];
for (NSObject *object in enumeratorKey) {
NSLog(@"key:%@", object);
}

NSEnumerator *enumeratorObject = [dictionary objectEnumerator];
for (NSObject *object in enumeratorObject) {
NSLog(@"value:%@", object);
}
NSLog(@"key name的值是:%@", [dictionary objectForKey:@"name"]);

}
return 0;
}

int main(int argc, const char * argv[])
{
    @autoreleasepool {
        NSDictionary *dictionary = [NSDictionary dictionaryWithObjectsAndKeys:@"25",@"age",@"张三",@"name",@"男",@"性别",nil];
        NSLog(@"%lu", [dictionary count]);
        NSEnumerator *enumeratorKey = [dictionary keyEnumerator];
        for (NSObject *object in enumeratorKey) {
            NSLog(@"key:%@", object);
        }
        
        NSEnumerator *enumeratorObject = [dictionary objectEnumerator];
        for (NSObject *object in enumeratorObject) {
            NSLog(@"value:%@", object);
        }
        NSLog(@"key name的值是:%@", [dictionary objectForKey:@"name"]);
        
    }
    return 0;
}

打印结果；

2012-07-09 16:31:18.276 objectiveC[2965:403] 3
2012-07-09 16:31:18.282 objectiveC[2965:403] key:age
2012-07-09 16:31:18.282 objectiveC[2965:403] key:name
2012-07-09 16:31:18.283 objectiveC[2965:403] key:性别
2012-07-09 16:31:18.283 objectiveC[2965:403] value:25
2012-07-09 16:31:18.284 objectiveC[2965:403] value:张三
2012-07-09 16:31:18.284 objectiveC[2965:403] value:男
2012-07-09 16:31:18.285 objectiveC[2965:403] key name的值是:张三

2、可变的词典NSMutableDictionary。

NSMutableDictionary是NSDictionary的子类，所以继承了NSDictionary的方法, 以上的代码对NSMutableDictionary来说完全可用。我们试试不一样的地方

增删键值数据。

[dictionary setObject: forKey:] :向可变的词典动态的添加数据

[dictionary removeAllObjects..] : 删除掉词典中的所有数据。

[dictionary removeObjectForKey..] :删除掉词典中指定key的数据

代码示例：

[cpp]
view plaincopyprint?

int main(int argc, const char * argv[])
{
@autoreleasepool {
NSMutableDictionary *dictionary = [NSMutableDictionary dictionaryWithObjectsAndKeys:@"25",@"age",@"张三",@"name",@"男",@"性别",nil];
[dictionary setObject:@"30名" forKey:@"名次"];

NSLog(@"%lu", [dictionary count]);
NSEnumerator *enumeratorKey = [dictionary keyEnumerator];
for (NSObject *object in enumeratorKey) {
NSLog(@"key:%@", object);
}

NSEnumerator *enumeratorObject = [dictionary objectEnumerator];
for (NSObject *object in enumeratorObject) {
NSLog(@"value:%@", object);
}
NSLog(@"key 名次的值是:%@", [dictionary objectForKey:@"名次"]);
[dictionary removeObjectForKey:@"名词"];
NSLog(@"%lu", [dictionary count]);
}
return 0;
}

int main(int argc, const char * argv[])
{
    @autoreleasepool {
        NSMutableDictionary *dictionary = [NSMutableDictionary dictionaryWithObjectsAndKeys:@"25",@"age",@"张三",@"name",@"男",@"性别",nil];
        [dictionary setObject:@"30名" forKey:@"名次"];
        
        NSLog(@"%lu", [dictionary count]);
        NSEnumerator *enumeratorKey = [dictionary keyEnumerator];
        for (NSObject *object in enumeratorKey) {
            NSLog(@"key:%@", object);
        }
        
        NSEnumerator *enumeratorObject = [dictionary objectEnumerator];
        for (NSObject *object in enumeratorObject) {
            NSLog(@"value:%@", object);
        }
        NSLog(@"key 名次的值是:%@", [dictionary objectForKey:@"名次"]);
        [dictionary removeObjectForKey:@"名词"];
        NSLog(@"%lu", [dictionary count]);
    }
    return 0;
}

打印结果：

2012-07-09 16:37:07.037 objectiveC[3053:403] 4
2012-07-09 16:37:07.042 objectiveC[3053:403] key:age
2012-07-09 16:37:07.043 objectiveC[3053:403] key:性别
2012-07-09 16:37:07.043 objectiveC[3053:403] key:name
2012-07-09 16:37:07.044 objectiveC[3053:403] key:名次
2012-07-09 16:37:07.044 objectiveC[3053:403] value:25
2012-07-09 16:37:07.045 objectiveC[3053:403] value:男
2012-07-09 16:37:07.045 objectiveC[3053:403] value:张三
2012-07-09 16:37:07.046 objectiveC[3053:403] value:30名
2012-07-09 16:37:07.046 objectiveC[3053:403] key 名次的值是:30名

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