添加到NSCompoundPredicate

Question

我想让我的代码更可重用于核心数据，我有一个带有谓词的fetchRequest，我总是必须使用它。然而，一些方法需要更多条件。我想将这些条件添加到谓词列表中，但我不确定如何执行此操作。我想要一个方法来返回带有基本查询的谓词，然后添加到那些查询。

 let fetchRequest = NSFetchRequest(entityName: "Stop")

        var currentTime = NSDate.getTime()

        var sort = NSSortDescriptor(key: "time", ascending: true) // sort by bus stop

        fetchRequest.sortDescriptors = [sort]

        let predicate = NSPredicate(format: "time >= %ld", currentTime)

        let predicate2 = NSPredicate(format: "stop_name == %@", stop)

        let predicate3 = NSPredicate(format: "busParent.direction == %@", direction)

        let predicate4 = NSPredicate(format: "busParent.name == %@", name)

        let predicate5 = NSPredicate(format: "busParent.schedule == %ld", schedule)

        fetchRequest.predicate = NSCompoundPredicate.andPredicateWithSubpredicates(
            [predicate, predicate2, predicate3, predicate4, predicate5])

        // EXAMPLE:  HOW WOULD I ADD TO THE COMPOUND PREDICATE ALREADY MADE?
        fetchRequest.predicate.????

Answer 1

您可以将NSCompoundPredicates与其他NSPredicates复合：

    let currentPredicate = fetchRequest.predicate!
    let additionalPredicate = NSPredicate(format: "whatever",...)
    let nextPredicate = NSCompoundPredicate(type: NSCompoundPredicateType.AndPredicateType, subpredicates: [currentPredicate, additionalPredicate])
    fetchRequest.predicate = nextPredicate

通过指定.AndPredicateType，您将＆＃34;缩小＆＃34;现有结果也适用于那些也符合额外谓词的结果。但您也可以指定OrPredicateType或NotPredicateType来添加或排除（分别）现有结果。