如何使用NSPredicate返回整个集/数组？

Question

我正在构建一个carArray并希望有条件地过滤内容,使用NSPredicate如下:

NSPredicate *pred;
switch (carType) {
  case FreeCar:
    pred = [NSPredicate predicateWithFormat:@"premium = NO"];
    break;
  case PremiumCar:
    pred = [NSPredicate predicateWithFormat:@"premium = YES"];
    break;
  default:
    pred = [NSPredicate predicateWithFormat:@"SOME PREDICATE THAT RETURNS EVERYTHING"];
    break;
}
self.carArray = [aCarArrayIGotFromSomewhere filteredArrayUsingPredicate:pred];

我的问题是,我存在的值的正确语法是什么,SOME PREDICATE THAT RETURNS EVERYTHING它返回数组/集中的所有实例？

Answer 1

要返回给定数组/集的所有内容:

迅速:

NSPredicate(value: true)

例如:

let array : NSArray = ["a", "b", "c", "d", "e"] let predicate = NSPredicate(value: true) array.filteredArrayUsingPredicate(predicate)

收益率:

["a", "b", "c", "d", "e"]

要排除给定数组/集的所有内容:

迅速:

NSPredicate(value: false)

例如:

let array : NSArray = ["a", "b", "c", "d", "e"] let predicate = NSPredicate(value: false) array.filteredArrayUsingPredicate(predicate)

收益率:

[]