ios NSPredicate 测试 NULL 和空白字符串
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NSPredicate to test for NULL, and blank strings
提问by Doz
I have an NSArrayand need to filter out any strings that are null or rather, have ' ' (empty string). How do I do that? I have tried doing:
我有一个NSArray并且需要过滤掉任何为空的字符串，或者更确切地说，有 ' ' （空字符串）。我怎么做？我试过这样做：
NSPredicate *predicateName = [NSPredicate predicateWithFormat:@"(name!=nil)"];
but that doesn't seem to work. Or maybe it does but there are different kinds of null...
但这似乎不起作用。或者也许确实如此，但是有不同种类的空...
回答by Dave DeLong
If you don't use Core Data, you could do:
如果你不使用 Core Data，你可以这样做：
NSPredicate *predicateName = [NSPredicate predicateWithFormat:@"name.length > 0"];
If the string is empty, this will fail (because 0 == 0). Similarly, if nameis nil, it will also fail, because [nil length] == 0.
如果字符串为空，这将失败（因为0 == 0）。同样，如果name是nil，它也会失败，因为[nil length] == 0。
回答by José Manuel Sánchez
I think this should work:
我认为这应该有效：
NSPredicate *predicateName = [NSPredicate predicateWithFormat:@"name!=nil AND name!=''"];
回答by chroww
NSPredicate *predicateName = [NSPredicate predicateWithFormat:@"name!=NULL"];
回答by Josip B.
This predicate worked for me:
这个谓词对我有用：
[NSPredicate predicateWithFormat:@"(%K== nil) OR %K.length == 0", @"imageUrl", @"imageUrl"]
