使用对象和键迭代 NSArray 的最快方法

发布于 2024-08-27 08:28:01 字数 332 浏览 5 评论 0原文

我有一个名为“objects”的 NSArray，其 arrayCount = 1000。迭代该数组大约需要 10 秒。有谁有更快的方法来迭代这个数组？

for (int i = 0; i <= arrayCount; i++) {
    event.latitude = [[[objects valueForKey:@"CLatitude"] objectAtIndex:i] floatValue];
    event.longitude = [[[objects valueForKey:@"CLongitude"] objectAtIndex:i] floatValue];
}

原文

I have an NSArray called 'objects' below with arrayCount = 1000. It takes about 10 secs to iterate through this array. Does anyone have a faster method of iterating through this array?

for (int i = 0; i <= arrayCount; i++) {
    event.latitude = [[[objects valueForKey:@"CLatitude"] objectAtIndex:i] floatValue];
    event.longitude = [[[objects valueForKey:@"CLongitude"] objectAtIndex:i] floatValue];
}

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池予 2024-09-03 08:28:01

迭代 NSArray 的最快方法是使用快速枚举。我的情况是：

for (id object in objects) {
    event.latitude = [[object valueForKey:@"CLatitude"] floatValue];
    event.longitude = [[object valueForKey:@"CLongitude"] floatValue]
}

The fastest way to iterate over an NSArray would be to use fast enumeration. I your case this would be:

for (id object in objects) {
    event.latitude = [[object valueForKey:@"CLatitude"] floatValue];
    event.longitude = [[object valueForKey:@"CLongitude"] floatValue]
}

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幽梦紫曦～ 2024-09-03 08:28:01

看起来 valueForKey 返回的数组在每次迭代中都是相同的，因此尝试在循环外获取对它们的引用：

NSArray *latitudes = [objects valueForKey:@"CLatitude"];
NSArray *longitudes = [objects valueForKey:@"CLongitude"];
for (int i = 0; i <= arrayCount; i++) {
    event.latitude = [[latitudes objectAtIndex:i] floatValue];
    event.longitude = [[longitudes objectAtIndex:i] floatValue];
}

但是循环的意义何在？最后，它不只是将事件属性设置为两个数组中的最后一个值吗？另外，如果 arrayCount 是元素数量，则循环应达到 i i i i i i i i i i i i i i i arrayCount 而不是 i <= arrayCount。

It looks like the arrays returned by valueForKey will be the same at every iteration so try obtaining a reference to them once outside the loop:

NSArray *latitudes = [objects valueForKey:@"CLatitude"];
NSArray *longitudes = [objects valueForKey:@"CLongitude"];
for (int i = 0; i <= arrayCount; i++) {
    event.latitude = [[latitudes objectAtIndex:i] floatValue];
    event.longitude = [[longitudes objectAtIndex:i] floatValue];
}

But what is the point of the loop? In the end, doesn't it just set the event properties to the last values in the two arrays? Also, if arrayCount is the number of elements then the loop should be up to i < arrayCount instead of i <= arrayCount.

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