在地图加载 Swift 3 之前从 API 加载纬度和经度

Question

我正在尝试显示一张带有两个标记的地图，其中包含从 API 检索的经度和纬度。

获取经度和纬度的函数在 Viewdidload 中调用

 override func viewDidLoad() {
    super.viewDidLoad()
    getCurrent()

还有显示带有标记的地图的代码viewdidload所以我的完整代码如下所示：

var longFamily  = ""
let latFamily = ""
var latShop = "" 
var longShop = "" 

override func viewDidLoad() {
    super.viewDidLoad()
    getCurrent()
    let coordinate₀ = CLLocation(latitude: CLLocationDegrees(Int(latFamily)!), longitude: CLLocationDegrees(Int(longFamily)!))
    let coordinate₁ = CLLocation(latitude: (Int(latFamily)!, longitude: (Int(longFamily)!))
    let distanceInMeters = coordinate₀.distance(from: coordinate₁) // result is in meters
    let floatDistance = Float(distanceInMeters)

    // get two markers with shop and client locations

    map.delegate = self
    // 2.
    let sourceLocation = CLLocationCoordinate2D(latitude: (Int(latFamily)!, longitude: (Int(longFamily)!)
    let destinationLocation = CLLocationCoordinate2D(latitude: (Int(latShop)!, longitude: (Int(latShop)!)

我知道在地图加载之前我必须做一些事情来获取数据，但不确定在哪里。我将不胜感激你的帮助

获取当前函数调用 API：

 Alamofire.request(url!, method: .get, parameters: param,encoding: URLEncoding.default, headers: headers).responseJSON { response in

        if let value: AnyObject = response.result.value as AnyObject? {
            //Handle the results as JSON

            let data = JSON(value)
            self.LongShop = data["shopLong"] 
     // this is for family locations too  

Answer 1

如果要在加载地图之前获得坐标，则需要在加载视图之前(在调用viewDidLoad之前(进行 API 调用。您可以尝试viewWillAppear，但根据 API 的响应时间，这可能不可靠。我建议在获得数据后立即调用 API。事先从用户或所需源获取param(可能在不同的视图中(，并将其传递给 prepareForSegue 函数中的地图视图：

1. 将全局变量添加到地图视图(例如.swift地图视图控制器(

   class MapViewController {
       var param: Any?    // replace Any with the desired data type
       /* rest of MapView code */
   }
   

2. 进行 API 调用并传入上一个视图控制器并将其传递给 MapViewController

   class PreviousViewController {
       var param: Any?    // replace Any with the desired data type
       override func viewDidLoad() {
           super.viewDidLoad()
           getFromAPI()    // getFromAPI being a function that makes the API call and assigns the param variable
       }
       func prepare(for segue: UIStoryboardSegue, sender: Any?) {
           if let dest = segue.destination as? MapViewController {
               dest.param = self.param
           }
       }
   }
   

除此之外，您还可以添加在未param之前无法执行 MapViewController segue 的功能nil