valueForKeyPath 的使用（真心不知道啊）

1	NSArray *testArray = [NSArray arrayWithObjects:@ "2.0" , @ "2.3" , @ "3.0" , @ "4.0" , nil];

2

3	NSNumber *sum = [testArray valueForKeyPath:@ "@sum.floatValue" ];

4

5	NSNumber *avg = [testArray valueForKeyPath:@ "@avg.floatValue" ];

6

7	NSNumber *avg = [testArray valueForKeyPath:@ "@max.floatValue" ];

8

9	NSNumber *avg = [testArray valueForKeyPath:@ "@min.floatValue" ];

valueForKeyPath计算求和、平均值、最大、最小

在检索NSArray的时候，通常可以利用循环把里面的对象一个一个比较找出目标。另外也可以通过Key-Value的方法找出对象。

例如有下面这么一个Array:

(

{

city = “Beijing”;

country = “China”;

},

{

city = “Tokyo”;

country = “Japan”;

},

{

city = “New York”;

country = “U.S.”;

}

)

通常可以通过循环来找出对象，如下:

NSDictionary *resultDic = nil;

for(NSDictionary *dic in array){

if([[dic objectForKey:@"city"] isEqualToString:@”Beijing”] ){

resultsDic = [dic retain];

break;

}

}

也可以通过key-value的方法来搜索:

[array valueForKeyPath:@"city"];

上述代码会返回:

(

“Beijing”,

“Tokyo”,

“New York”

)

然后利用如下的代码获取array的index:

[[array valueForKeyPath:@"city"] indexOfObject:@”Beijing”];

然后用取得的index获取对象就可以:

[array objectAtIndex:[[array valueForKeyPath:@"city"] indexOfObject:@”Beijing]];

------------------------------------------------------------------------------------------------------------------------------------

NSMutableDictionary *dic=[NSMutableDictionary dictionary];

[dic setObject:@"v1" forKey:@"k1"];

[dic setObject:@"v2" forKey:@"k2"];

[dic setObject:@"v3" forKey:@"k3"];

NSArray *array=[NSArray arrayWithObjects:@"2",@"3",@"4",@"5",nil];

[dic setObject:array forKey:@"k4"];

id obj=[dic valueForKeyPath:@"k4.@sum.floatValue"];

NSLog(@"%@",[obj description]);//==14

找不到出处 从此处的来：http://blog.csdn.net/binyanye1/article/details/43413333