iOS - 使用谓词过滤集的性能

Question

我在一些较旧的设备上遇到UI口吃/暂停（例如ipod touch 4th gen），我将其缩小到这段代码：

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"gender != %@ && catId != %@", [NSNumber numberWithInt:0], [NSNumber numberWithInt:7]];
NSSet *filteredCats = [cats filteredSetUsingPredicate:predicate]; //cats is an NSSet

如果我注释掉这两行代码并改为执行此操作：

NSSet *filteredCats = cats;

表现非常流畅。那么如何在不引起屏幕更新的短暂停顿的情况下改进此过滤呢？

Answer 1

您可以异步进行过滤，这有助于提高性能：

 __weak ViewController *bSelf = self;
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0ul),^{

    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"gender != %@ && catId != %@", [NSNumber numberWithInt:0], [NSNumber numberWithInt:7]];

    NSSet *filteredCats = [cats filteredSetUsingPredicate:predicate]; 

    dispatch_async(dispatch_get_main_queue(), ^{ 
        [bSelf updateMyViewWithFilteredSet:filteredCats]; 
    }
}