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.”;
}
)
{
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;
}
}
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”
)
“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
最后
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