初始化后如何从函数中获取值？

Posted 2023-03-05

【中文标题】初始化后如何从函数中获取值？

【英文标题】：How to get value from function after it has already been initialised?

【发布时间】：2017-09-18 10:30:16

【问题描述】：

我从 Firebase 获取我的坐标，然后将它们放在我的地图上，但问题是我的 Firebase 获取指令发生在地图初始化标记之后，在我的坐标中给出 nil。

如何从 Firebase 中获取值并将它们作为标记？

var fetchLat: Double!
var fetchLong: Double!

我在这里从 Firebase 获取值

func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation])

    let camera = GMSCameraPosition.camera(withLatitude: latPass, longitude: longPass, zoom: 5)
    let mapView = GMSMapView.map(withFrame: CGRect.zero, camera: camera)
    view = mapView
    mapView.settings.scrollGestures = true
    mapView.settings.zoomGestures = true
    mapView.settings.myLocationButton = true

    let dataBaseRef=FIRDatabase.database().reference()
    dataBaseRef.child("LocationTest").queryOrderedByKey().observe(.childAdded, with: (snapshot) in

        let postDict = snapshot.value as? [String : AnyObject] ?? [:]
        var fetchLat = postDict["lat"] as! Double
        var fetchLong = postDict["long"] as! Double
)

我把它们放在地图上

    let friendLocator = [
        Locator(name: "Virat", long: fetchLong, lat: fetchLat),
    ]

    for friend in friendLocator

        let friendMarker = GMSMarker()
        friendMarker.position=CLLocationCoordinate2D(latitude: friend.lat, longitude: friend.long)
        friendMarker.title=friend.name
        friendMarker.map=mapView
        mapView.selectedMarker=friendMarker
    

因为地图初始化是在从 Firebase 获取值之前完成的，所以在获取值之后如何设置标记？

【问题讨论】：

为什么在 didUpdateLocations 中调用 firebase 获取请求。

@Pushpendra 因为我在didUpdateLocations中添加了我的标记

@naveen-saini : view = mapView 那里的视图是什么？ Self.view 或单独的 UIView 变量名为 view ??

@SandeepBhandari 只是self.view

@naveen-saini ：这意味着你的 self.view 是 GMSMapView 类型，那么你不需要在另一个函数中引用 mapView ，你可以简单地说 self.view.selectedMarker=friendMarker

【参考方案1】：

如果在地图上显示用户的 ViewController 与 LocationManager 的代理相同，那么，

在您的 ViewController 中创建一个属性，

var friendLocator : [Locator] = [Locator]()

创建一个在地图上绘制用户的函数

func locateFriends() 
        if self.view is GMSMapView 
            for friend in friendLocator 
                let friendMarker = GMSMarker()
                friendMarker.position=CLLocationCoordinate2D(latitude: friend.lat, longitude: friend.long)
                friendMarker.title=friend.name
                friendMarker.map= (self.view as! GMSMapView)
                (self.view as! GMSMapView).selectedMarker=friendMarker
            
        
    

最后将新找到的定位器实例追加到didUpdateLocationsdelegate中的数组

extension ViewController : UIPageViewControllerDelegate 
    func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation])
    

        let dataBaseRef=FIRDatabase.database().reference()
        dataBaseRef.child("LocationTest").queryOrderedByKey().observe(.childAdded, with: (snapshot) in

            let postDict = snapshot.value as? [String : AnyObject] ?? [:]
            var fetchLat = postDict["lat"] as! Double
            var fetchLong = postDict["long"] as! Double

            let locator = Locator(name: "Virat", long: fetchLong, lat: fetchLat)
            //do some sort of duplicate check before blindly adding new locator to array
            self.friendLocator.append(locator)
            self.locateFriends()
        )
    

如果在地图上显示用户的 ViewController 不同，则 UILocationManager 委托使用相同的逻辑，但使用delegate 模式通知 ViewController 新的定位器对象并重新加载地图。

编辑：

重新格式化 OP 的代码

import MapKit

import UIKit

import CoreLocation

import GoogleMaps

import GooglePlaces

import GoogleMapsCore

import Firebase

import FirebaseDatabase


struct postStruct

    let lat: Double!

    let long: Double!




class ViewController: UIViewController,MKMapViewDelegate, CLLocationManagerDelegate, UISearchBarDelegate


    var viratPin=CustomPointAnnotation()

    var posts=[postStruct]()
    var mapView : GMSMapView? = nil


    var friendLocator : [Locator] = [Locator]()



    @IBOutlet weak var searchBar: UISearchBar!

    @IBOutlet weak var searchSupporter: UIView!

    @IBAction func dismissKeyboard(_ sender: Any) 

        searchBar.resignFirstResponder()

    



    struct Locator 

        let name: String

        let long: CLLocationDegrees

        let lat: CLLocationDegrees

    



    class CustomPointAnnotation: MKPointAnnotation 

        var imageName: String!

    



    let manager = CLLocationManager()

    var myLocation: CLLocationCoordinate2D?

    var friend1: CLLocationCoordinate2D?

    var arbokPin = CustomPointAnnotation()

    var location=0

    var latPass: Double!

    var longPass: Double!

    var fetchLat: Double!

    var fetchLong: Double!



    func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation])

    

        var location=locations[0]

        let span:MKCoordinateSpan=MKCoordinateSpanMake(0.01, 0.01)

        var myLocation:CLLocationCoordinate2D=CLLocationCoordinate2DMake(location.coordinate.latitude, location.coordinate.longitude)

        let region:MKCoordinateRegion=MKCoordinateRegionMake(myLocation, span)

        latPass=location.coordinate.latitude

        longPass=location.coordinate.longitude


        post()

        self.configureMapView()

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

        dataBaseRef.child("LocationTest").queryOrderedByKey().observe(.childAdded, with: (snapshot) in



            let postDict = snapshot.value as? [String : AnyObject] ?? [:]

            var fetchLat = postDict["lat"] as! Double

            var fetchLong = postDict["long"] as! Double


            let locator = Locator(name: "You", long: fetchLong, lat: fetchLat)
            self.friendLocator.append(locator)
            self.locateFriend()
        )

        manager.stopUpdatingLocation()

        self.view = mapView
    


    func configureMapView() 
        let camera = GMSCameraPosition.camera(withLatitude: latPass, longitude: longPass, zoom: 5)

        self.mapView = GMSMapView.map(withFrame: CGRect.zero, camera: camera)

        view = mapView

        mapView.settings.scrollGestures = true

        mapView.settings.zoomGestures = true

        mapView.settings.myLocationButton = true

        mapView.addSubview(searchBar)

        mapView.addSubview(searchSupporter)

        mapView.bringSubview(toFront: searchBar)


        for gesture in mapView.gestureRecognizers! 

            mapView.removeGestureRecognizer(gesture)

        
    

    func locateFriend() 
        for friend in friendLocator
            let friendMarker = GMSMarker()

            friendMarker.position=CLLocationCoordinate2D(latitude: friend.lat, longitude: friend.long)

            friendMarker.title=friend.name

            friendMarker.map=mapView

            mapView.selectedMarker=friendMarker

            if friend.name=="Virat"

                friendMarker.icon=UIImage(named: "ViratPin.png")

            

            else if friend.name=="Naveen"

                friendMarker.icon=UIImage(named: "naveenPin.png")

            

            else if friend.name=="You"

                friendMarker.icon=UIImage(named: "currentLocation.png")

            

        

        do 

            mapView.mapStyle = try GMSMapStyle(jsonString: kMapStyle)

         catch 

            NSLog("One or more of the map styles failed to load. \(error)")

        
    

    override func viewDidLoad() 

        super.viewDidLoad()



        manager.delegate=self

        manager.desiredAccuracy=kCLLocationAccuracyBest

        manager.requestWhenInUseAuthorization()

        manager.startUpdatingLocation()

        searchBar.isUserInteractionEnabled=true

        searchBar.delegate=self

        searchSupporter.alpha=0



    





    func searchBarTextDidBeginEditing(_ searchBar : UISearchBar)

        self.searchSupporter.alpha=0.8

        print("yes")

    



    func searchBarTextDidEndEditing(_ searchBar: UISearchBar) 

        searchSupporter.alpha=0

        print("no")

    



    func searchBarSearchButtonClicked(_ searchBar: UISearchBar) 

        print(searchBar.text!)


    


    override var prefersStatusBarHidden: Bool

        return true

    

    func post()

        let post : [String: Double]=["lat":latPass, "long":longPass]

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

        //dataBaseRef.child("Location").childByAutoId().setValue(post)

        dataBaseRef.child("Location").child("id").setValue(post)


    

【讨论】：

我的mapView 是在didUpdateLocations 中初始化的，所以我不能在另一个函数中使用它。

@naveen-saini : 我在 didUpdateLocations 中没有看到任何地图初始化代码

@naveen-saini ：如果它在 didUpdateLocations 中初始化，您可以为 map 创建一个可选变量，并使其成为您的 ViewController 的实例属性，并在您的 didUpdateLocations 中将其用作 self.mapView，最后在locateFriends 函数在添加 GMSMarker 之前检查 self.mapView != nil thats all

@naveen-saini : 给我一秒钟

@naveen-saini : 立即查看