上下文类型“Void”（又名“()”）不能与数组字面量一起使用

Question

我的代码中出现此错误：

Contextual type 'Void' (aka '()') cannot be used with array literal

我应该如何解决这个问题？谢谢！

我正在使用 MVC 模型。这是我的代码：

let users: [User] = {

    let ref = FIRDatabase.database().reference().child("position")
    ref.observeSingleEvent(of: .childAdded, with: { (snapshot) in

        if let locationDict = snapshot.value as? [String: AnyObject] {

            guard let lat = locationDict["latitude"] as? CLLocationDegrees,
                let long = locationDict["longitude"] as? CLLocationDegrees else { return }

            let position = CLLocationCoordinate2D(latitude: lat, longitude: long)
            let userPosition = User(name: "Name", position: position)

            return [userPosition] //Here is my error 


        }


    })

}()

 override func cellClasses() -> [DatasourceCell.Type] {
    return [UserCell.self]
}

override func item(_ indexPath: IndexPath) -> Any? {
    return users[indexPath.item]
}

override func numberOfItems(_ section: Int) -> Int {
    return users.count
}



}

我的用户属性：

import Foundation
import MapKit

struct User {

let name: String
let position: CLLocationCoordinate2D



}

还有我的细胞：

import LBTAComponents
import MapKit
import CoreLocation

class UserCell: DatasourceCell, CLLocationManagerDelegate, MKMapViewDelegate  {

let distanceSpan: Double = 500


override var datasourceItem: Any? {
    didSet {
        guard let user = datasourceItem as? User else { return }
        nameLabel.text = user.name
        MapView.setCenter(user.position, animated: false)

        MapView.region = MKCoordinateRegion(center: user.position, span: MKCoordinateSpan(latitudeDelta: 0.01, longitudeDelta: 0.01))

        let locationPin = user.position
        let annotation = MKPointAnnotation()
        annotation.coordinate = locationPin

        MapView.addAnnotation(annotation)
        MapView.showAnnotations([annotation], animated: true)     

        }

   }

Answer 1

您正在为users 分配一个闭包，它被声明为[User] 类型（带有User 类型元素的数组）。

当您使用 MVC 时，我假设代码在 UIViewController 中使用这个（未经测试，但您明白了）：

import CoreLocation

struct User {
    var name:String
    var position:CLLocationCoordinate
}

class MyViewController: UIViewController {
    var ref = FIRDatabase.database().reference().child("position")
    var users: [User]?

    override func viewDidLoad() {
        super.viewDidLoad()
        setupRefObserver()
    }

    private func setupRefObserver() {
        ref.observeSingleEvent(of: .childAdded, with: { (snapshot) in
            if let locationDict = snapshot.value as? [String: AnyObject] {

                guard let lat = locationDict["latitude"] as? CLLocationDegrees,
                    let long = locationDict["longitude"] as? CLLocationDegrees else { return }

                let position = CLLocationCoordinate2D(latitude: lat, longitude: long)
                let userPosition = User(name: "Name", position: position)

                users = [userPosition]
            }
        })
    }
}