在完成块之外使用变量 [英] using variables outside of completion block

问题描述

我目前正在从 firebase 检索数据，数据被放入一个 NSObject 然后是一个完成块.完成块内的项目存储为变量 userBinfos.变量 userBinfos 只在完成块内工作我想在完成之外使用它

Im currently retrieving data from firebase the data is put inside an NSObject and then a completion block. The item inside of the completion block is store as a variable userBinfos. Variable userBinfos only work inside of the completion block i want to use this outside of the completion

var userBinfos = userObject()
    override func viewDidLoad() {
        super.viewDidLoad()

        userBinfo { (user) in
        self.userBinfos = user

        }  
//I want to use to variable here but it does not work 
        print(self.userBinfos.email)

    }


    func userBinfo(completion: (userObject) -> ()) {

        let dbFir = FIRDatabase.database().reference()

        let firRef = dbFir.child("frontEnd/users/(userId)")

        firRef.observeEventType(.Value, withBlock: { snapshot in

            let userDict = snapshot.value as! [String: AnyObject]
            self.name.text = userDict["firstname"] as? String
            self.userBio.text = userDict["userBio"] as! String

            var user = userObject()

            user.firstName = userDict["firstname"]
            user.lastName = userDict["lastname"]
            user.email = userDict["email"]
            user.profileImageUrl = userDict["profileImageUrl"]
            user.userBio = userDict["firstname"]
            user.userId = userDict["firstname"]

                   dispatch_async(dispatch_get_main_queue(), {
            completion(user)

            })

        }) { (error) in
            print(error)
        }

    }

推荐答案

userBinfo 的 completion 参数的全部目的是提供一种机制，当异步 observeEventType 被调用.因此，将代码取决于异步方法的完成inside userBinfo { user in ... } 闭包.

The entire purpose of the completion parameter of userBinfo is to provide a mechanism for being informed when the asynchronous observeEventType is called. So put code contingent upon the completion of that asynchronous method inside the userBinfo { user in ... } closure.

如果在调用异步 completion 闭包之前部分 UI 没有意义，则让 viewDidLoad 配置 UI 以使其显式(可能显示UIActivityIndi​​catorView 或其他)，然后在完成处理程序中删除那些东西.

And if part of the UI doesn't make sense until that asynchronous completion closure is called, then have viewDidLoad configure the UI to make that explicit (perhaps show a UIActivityIndicatorView or whatever) and then remove that stuff inside the completion handler.

override func viewDidLoad() {
    super.viewDidLoad()

    // do whatever you want to let the user know that something asynchronous
    // is happening, e.g. add a spinning `UIActivityIndicatorView` or whatever

    userBinfo { user in
        self.userBinfos = user

        // Update the UI here, including removing anything we presented to let
        // the user know that the asynchronous process was underway. If you were
        // dealing with UITableView`, you'd call `tableView.reloadData()` here.
    }  

    // but not here
}

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