swift - 在另一个函数中使用一个函数的输出？

Question

我有一个获取请求，我想使用结果来通知其他函数。获取的是

   func getExercises() {

    guard let managedObjectContext = managedObjectContext else { return }
    let userExercise = UserExercise(context: managedObjectContext)

    let request: NSFetchRequest<UserExercise> = UserExercise.fetchRequest()
    request.predicate = NSPredicate(format: "usersroutine == %@", self.routineName)
    do {
        let appDelegate = UIApplication.shared.delegate as! AppDelegate
        let context = appDelegate.persistentContainer.viewContext
        let queryResults = try context.fetch(request)
        print ("num of results = \(queryResults.count)")
            for exercise in queryResults as [NSManagedObject] {
        print("Exercise NAME: \(exercise.value(forKey: "name"))")
        }
    } catch {
        print("Error with request: \(error)")
    }

其他功能是(在 id 希望输出的位置添加大写字母):

    func configure(_ cell: TodaysRoutineTableViewCell, at indexPath: IndexPath) {
    let userExercise = THE GET EXERCISE FUNCTIONS OUTPUT(at: indexPath)

还有另一个:

    fileprivate func updateView() {
    var hasUserExercises = false
    if let UserExercise = THE GET EXERCISE FUNCTIONS OUTPUT {
        hasUserExercises = UserExercise.count > 0
    }

我想也许 id 只是在其中添加 queryResults 就可以了，但由于那是该函数的本地函数，所以我只会收到错误。实现这一目标的正确方法是什么？

已更新以显示错误图像

    // MARK: - COREDATA FETCH

func getExercises(completion: (([NSManagedObject]?, NSError?) -> Void)?) {

    guard let managedObjectContext = managedObjectContext else { return }
    let userExercise = UserExercise(context: managedObjectContext)

    let request: NSFetchRequest<UserExercise> = UserExercise.fetchRequest()
    request.predicate = NSPredicate(format: "usersroutine == %@", self.routineName)

    do {
        let appDelegate = UIApplication.shared.delegate as! AppDelegate
        let context = appDelegate.persistentContainer.viewContext

        let exercises: [NSManagedObject]?

        do {
            let queryResults = try context.fetch(request)
            print(queryResults)

            for exercise in queryResults as [NSManagedObject] {
                print("Exercise NAME: \(exercise.value(forKey: "name"))")
            }
            completion(exercises, nil)

        } catch {
            print("Error with request: \(error)")
            completion(exercises, error)
        }
    }
}

Answer 1

1. Use of unresolved identifier 'exercises'

根据您在图像中显示的代码，您第一个错误的原因是，您使用了尚未声明的属性exercises。 completion 闭包参数中的 exercises 将无法在该函数中访问。它是一个需要传递给该闭包的参数。

当您调用完成 block 时，您必须将一个 NSManagedObject 数组传递给它，该数组是您在获取结果后构造的。在您的情况下，在 for..in 循环中构造一个数组，并在该循环之后调用完成 block 。

let exercises: [NSManagedObject]?

do {
    let queryResults = try context.fetch(request)
    print(queryResults)

    for exercise in queryResults as [NSManagedObject] {
        //Using the result, build the exercises array here
    }

    completion(exercises, nil)
} catch {
     print("Error with request: \(error)")
    completion(exercises, error)
}

2. Nil is not compatible with expected argument type '[NSManagedObject]'

这是因为 exercises 参数不是可选的，但您将 nil 传递给它。您必须将exercises参数设为可选，才能同时采用非nil和nil值。将您的方法签名更改为以下内容:

func getExercises(completion: ((exercises: [NSManagedObject]?, error: NSError?) -> Void)?)

注意:确保在传递给 getExercises 函数的完成闭包中正确处理 nil。