在subarrayWithRange中防止NSRangeException [英] Prevent NSRangeException in subarrayWithRange

问题描述

我有这个代码，它允许我传入索引，并有选择地检索数组中的一些图像一定的范围长度 - 取决于方向。

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.

当在纵向时，范围应该是每个索引20个项目，并且我总共有43个项目。但是当我传入最后一个索引时，我得到超出[0..42]范围的索引59超出范围的异常。

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;

我如何防止这种情况？

谢谢。

推荐答案

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

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