NSSet 的 NSArray 在 NSLog 中没有显示任何内容

发布于 2024-12-18 09:00:52 字数 572 浏览 1 评论 0原文

NSMutableSet *intersection = [NSMutableSet setWithArray:newsmall];

//this shows an array of newsmall as expected
NSLog(@"intersection %@", intersection);

[intersection intersectSet:[NSSet setWithArray:newnewbig]];

//this shows nothing
NSLog(@"intersection %@", intersection);

//this shows an array of newnewbig as expected
NSLog(@"newnewbig %@", newnewbig);

NSArray *arrayfour = [intersection allObjects];

//this shows nothing
NSLog(@"arrayfour %@", arrayfour);

newsmall 和 newnewbig 有一些匹配的字符串，因此我希望 arrayfour 显示几个字符串。

我做错了什么？

原文

NSMutableSet *intersection = [NSMutableSet setWithArray:newsmall];

//this shows an array of newsmall as expected
NSLog(@"intersection %@", intersection);

[intersection intersectSet:[NSSet setWithArray:newnewbig]];

//this shows nothing
NSLog(@"intersection %@", intersection);

//this shows an array of newnewbig as expected
NSLog(@"newnewbig %@", newnewbig);

NSArray *arrayfour = [intersection allObjects];

//this shows nothing
NSLog(@"arrayfour %@", arrayfour);

newsmall and newnewbig have some matched strings, so I expect arrayfour to show a couple of strings.

What did I do wrong?

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感性 2024-12-25 09:00:52

问题在于您对 intersectSet 工作原理的理解。

我认为您期望它比较 newsmall 和 newnewbig 的字符串内容，但它真正做的是比较对象地址。

在执行 intersectSet 调用之前执行此操作：

NSUInteger index = 0;
for(NSString * aString in newsmall)
{
    NSLog( @"newsmall string %d is %p %@", index++, aString, aString );
} 

index = 0;
for(NSString * aString in newnewbig)
{
    NSLog( @"newnewbig string %d is %p %@", index++, aString, aString );
}

只有当地址（格式中的 %p）匹配时，intersectSet 才会起作用。字符串内容可能匹配，但 intersectSet 关心的是字符串地址。

所以实际上，您的解决方案是您需要采用不同的方式来比较集合之间的字符串。

The problem is in your understanding of how intersectSet works.

I think you are expecting it to compare contents of the strings from newsmall and newnewbig, but what it's really doing is comparing object addresses.

Do this before you do the intersectSet call:

NSUInteger index = 0;
for(NSString * aString in newsmall)
{
    NSLog( @"newsmall string %d is %p %@", index++, aString, aString );
} 

index = 0;
for(NSString * aString in newnewbig)
{
    NSLog( @"newnewbig string %d is %p %@", index++, aString, aString );
}

intersectSet will only work if the address (the %p in the formatting up there) matches. The string contents might match, but what intersectSet cares about is the string address.

So really, your solution is that you need to do a different way of comparing strings between sets.

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