如何在NSSet或NSArray中搜索具有特定属性特定值的对象?

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"type == %@", @"standard"];
NSArray *filteredArray = [myArray filteredArrayUsingPredicate:predicate];
id firstFoundObject = nil;
firstFoundObject =  filteredArray.count > 0 ? filteredArray.firstObject : nil;

注意:这个概念

您可以得到Jason和Ole所描述的过滤数组,但是因为您只需要一个对象,所以我将使用 - indexOfObjectPassingTest: (如果在数组中)或 -objectPassingTest: (如果它在一个集合中)并避免创建第二个数组。

一般来说,我用 indexOfObjectPassingTest: 因为我发现用Objective-C代码表示测试比用 NSPredicate integerValue 实际上是一处房产):

NSArray *array = @[@0,@1,@2,@3];
NSUInteger indexOfTwo = [array indexOfObjectPassingTest:^BOOL(id obj, NSUInteger idx, BOOL *stop) {
    return ([(NSNumber *)obj integerValue] == 2);
}];
NSUInteger indexOfFour = [array indexOfObjectPassingTest:^BOOL(id obj, NSUInteger idx, BOOL *stop) {
    return ([(NSNumber *)obj integerValue] == 4);
}];
BOOL hasTwo = (indexOfTwo != NSNotFound);
BOOL hasFour = (indexOfFour != NSNotFound);
NSLog(@"hasTwo: %@ (index was %d)", hasTwo ? @"YES" : @"NO", indexOfTwo);
NSLog(@"hasFour: %@ (index was %d)", hasFour ? @"YES" : @"NO", indexOfFour);

此代码的输出为:

hasTwo: YES (index was 2)
hasFour: NO (index was 2147483647)

NSArray* results = [theFullArray filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@"SELF.type LIKE[cd] %@", @"standard"]];