尝试 return 函数中的数组时收到未解析的标识符

Question

我收到一个错误：“在尝试 return 数据数组时使用了未解析的标识符 'data'。我的代码列在下面。有人可以告诉我为什么会这样吗？

    public func loadData()->[Q] {
    let publicData = CKContainer.default().publicCloudDatabase
    let pred = NSPredicate(value: true)
    let query = CKQuery(recordType: "question", predicate: pred)
    publicData.perform(query, inZoneWith: nil, completionHandler: ({results, error in
        if(error != nil) {
            print(error?.localizedDescription)
        } else {
            if results!.count > 0 {
                var data = [Q]()
                for result in results!{
                    let quest = result.object(forKey: "question_name") as! String!
                    let a = result.object(forKey: "a") as! String!
                    let b = result.object(forKey: "b") as! String!
                    let c = result.object(forKey: "c") as! String!
                    let d = result.object(forKey: "d") as! String!
                    let answer = result.object(forKey: "answer") as! String!
                    let category = result.object(forKey: "category") as! String!
                    let final = Q(quest: quest!, A:a!, B: b!, C: c!, D: d!, answer: answer!, category: category!)
                    data.append(final)
                }
            }
        }
    }))
    return data
}

Answer 1

不！不！不！，永远不会使用sleep解决异步任务！太可怕了。

为方便起见，使用 success 和 failure 个案例和关联类型创建枚举
```
enum Result {
  case success([Q]), failure(Error)
}
```

在loadDatareturndata或error中完成处理程序。我删除了一堆多余的括号、感叹号和数组的空检查。在没有错误且没有匹配数据的情况下，Q 的空数组被 returned.

public func loadData(completion: @escaping (Result)->() ) {
  let publicData = CKContainer.default().publicCloudDatabase
  let pred = NSPredicate(value: true)
  let query = CKQuery(recordType: "question", predicate: pred)
  publicData.perform(query, inZoneWith: nil, completionHandler: {results, error in
    if error != nil {
     completion(.failure(error!))
    } else {
      var data = [Q]()
      for result in results! {
        let quest = result.object(forKey: "question_name") as! String
        let a = result.object(forKey: "a") as! String
        let b = result.object(forKey: "b") as! String
        let c = result.object(forKey: "c") as! String
        let d = result.object(forKey: "d") as! String
        let answer = result.object(forKey: "answer") as! String
        let category = result.object(forKey: "category") as! String
        let final = Q(quest: quest, A:a, B: b, C: c, D: d, answer: answer, category: category)
        data.append(final)
      }
      completion(.success(data))
    }
  })
}

调用函数

loadData { result in
  switch result {
  case .success(let data): print(data) // do something with the result
  case .failure(let error): print(error)
  }
}

尝试 return 函数中的数组时收到未解析的标识符

unresolved identifier received when trying to return an array in function

swift

cloudkit