ios 如何使用字符串值获取 NSArray 中对象的索引？
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How do I get the index of an object in an NSArray using string value?
提问by jroyce
I want to get the index of an object within the NSMutableArray of categories.
我想在 NSMutableArray 的类别中获取对象的索引。
The category object has an attribute "category_title" and I want to be able to get the index by passing the value of category_title.
类别对象有一个属性“category_title”，我希望能够通过传递 category_title 的值来获取索引。
I have looked through the docs and can't find a simple way to go about this.
我已经浏览了文档，但找不到一个简单的方法来解决这个问题。
回答by Conrad Shultz
NSArraydoes not guarantee that you can only store one copy of a given object, so you have to make sure that you handle that yourself (or use NSOrderedSet).
NSArray不保证您只能存储给定对象的一个副本，因此您必须确保自己处理（或使用NSOrderedSet）。
That said, there are a couple approaches here. If your category objects implement isEqual:to match category_title, then you can just use -indexOfObject:.
也就是说，这里有几种方法。如果您的类别对象实现isEqual:匹配 category_title，那么您只需使用-indexOfObject:.
If you can't do that (because the category objects use a different definition of equality), use -indexOfObjectPassingTest:. It takes a block in which you can do whatever test you want to define your "test" - in this case, testing category_titlestring equality.
如果您不能这样做（因为类别对象使用不同的相等定义），请使用-indexOfObjectPassingTest:. 它需要一个块，您可以在其中执行您想要定义“测试”的任何测试 - 在这种情况下，测试category_title字符串相等性。
Note that these are all declared for NSArray, so you won't see them if you are only looking at the NSMutableArrayheader/documentation.
请注意，这些都是为 声明的NSArray，因此如果您只查看NSMutableArray标题/文档，则不会看到它们。
EDIT: Code sample. This assumes objects of class CASCategorywith an NSStringproperty categoryTitle(I can't bring myself to put underscores in an ivar name :-):
编辑：代码示例。这假定类的对象CASCategory具有NSString属性categoryTitle（我不能让自己在 ivar 名称中添加下划线 :-)：
CASCategory *cat1 = [[CASCategory alloc] init];
[cat1 setCategoryTitle:@"foo"];
CASCategory *cat2 = [[CASCategory alloc] init];
[cat2 setCategoryTitle:@"bar"];
CASCategory *cat3 = [[CASCategory alloc] init];
[cat3 setCategoryTitle:@"baz"];
NSMutableArray *array = [NSMutableArray arrayWithObjects:cat1, cat2, cat3, nil];
[cat1 release];
[cat2 release];
[cat3 release];
NSUInteger barIndex = [array indexOfObjectPassingTest:^BOOL(id obj, NSUInteger idx, BOOL *stop) {
if ([[(CASCategory *)obj categoryTitle] isEqualToString:@"bar"]) {
*stop = YES;
return YES;
}
return NO;
}];
if (barIndex != NSNotFound) {
NSLog(@"The title of category at index %lu is %@", barIndex, [[array objectAtIndex:barIndex] categoryTitle]);
}
else {
NSLog(@"Not found");
}
回答by Bruce Dean
Not sure that I understand the question but something like this might work (assuming the Mutable Array contains objects of Class "Category"):
不确定我是否理解这个问题，但这样的事情可能会起作用（假设可变数组包含“类别”类的对象）：
int indx;
bool chk;
for (Category *aCategory in theArray)
{
chk = ([[aCategory category_title] isEqualToString:@"valOfCategoryTitle"])
if ( chk )
indx = [theArray indexOfObject:aCategory];
}
回答by Leena
Try this code much more simpler:-
试试这个更简单的代码：-
int f = [yourArray indexOfObject:@"yourString"];
