防止 subarrayWithRange 中出现 NSRangeException

发布于 2024-10-04 16:09:43 字数 700 浏览 2 评论 0原文

我有这段代码，它允许我传入一个索引，并有选择地检索数组中一定范围长度的多个图像 - 取决于方向。

当处于纵向时，范围应该是每个索引 20 个项目，我总共有 43 个项目。但是，当我传入最后一个索引时，我收到索引 59 超出 [0..42] 范围的异常。

NSArray *tempArray = [self imageData];

UIDeviceOrientation devOr = [[UIDevice currentDevice] orientation];

int kItemsPerView;

if (UIDeviceOrientationIsPortrait(devOr)) {
    kItemsPerView = 20;
}else {
    kItemsPerView = 14;
}

NSRange rangeForView = NSMakeRange( index * kItemsPerView, kItemsPerView ); 

NSArray *subArray = [[tempArray subarrayWithRange:rangeForView] retain];
NSMutableArray *imagesForView = [NSMutableArray arrayWithArray:subArray];
[subArray release];

return imagesForView;

我怎样才能防止这种情况？

谢谢。

原文

I have this code which allows me to pass in an index, and selectively retrieve, a number of images in an array for a certain range length - depending on orientation.

When in portrait the range should be be 20 items per index, and i have 43 items altogether. However when i pass in the last index, i get an out of range exception for index 59 beyond bounds of [0..42].

NSArray *tempArray = [self imageData];

UIDeviceOrientation devOr = [[UIDevice currentDevice] orientation];

int kItemsPerView;

if (UIDeviceOrientationIsPortrait(devOr)) {
    kItemsPerView = 20;
}else {
    kItemsPerView = 14;
}

NSRange rangeForView = NSMakeRange( index * kItemsPerView, kItemsPerView ); 

NSArray *subArray = [[tempArray subarrayWithRange:rangeForView] retain];
NSMutableArray *imagesForView = [NSMutableArray arrayWithArray:subArray];
[subArray release];

return imagesForView;

How can i prevent this?

Thanks.

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以为你会在 2024-10-11 16:09:43

if ((index * kItemsPerView + kItemsPerView) >= tempArray.count)
     rangeForView = NSMakeRange( index * kItemsPerView, tempArray.count-index*kItemsPerView );

if ((index * kItemsPerView + kItemsPerView) >= tempArray.count)
     rangeForView = NSMakeRange( index * kItemsPerView, tempArray.count-index*kItemsPerView );

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哆啦不做梦 2024-10-11 16:09:43

另一种方法，只需使用 MIN() 函数来确定范围的结尾。

例子：

NSRange range;
range.location = index * kItemsPerView;
range.length = MIN(kItemsPerView, tempArray.count - range.location);
NSArray *imagesForView = [tempArray subarrayWithRange:range];

Alternate approach, just use MIN() function for determining the end of the range.

Example:

NSRange range;
range.location = index * kItemsPerView;
range.length = MIN(kItemsPerView, tempArray.count - range.location);
NSArray *imagesForView = [tempArray subarrayWithRange:range];

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