SwiftUI - 获取要在 API 调用中传递的用户坐标

Question

这个问题已经困扰我好几个月了，我相信这是因为我使用了错误的结构和过程。

我正在尝试对Yelp的API进行API调用，并为用户的lat/long传递变量。我可以根据我当前的LocationManager获取lat/long，但是，当lat/long似乎只有在API调用后才可用时，因此API将获得两个lat/long的默认值0.0。

说到这一点，我还是个初学者，但有没有办法设置一个加载屏幕，在后台抓取纬度/经度，当我的ExploreView显示时，真正的位置信息已经建立？

下面是我的LocationManager和ExploreView

LocationManager

import Foundation
import CoreLocation
class LocationManager: NSObject, ObservableObject {
private let locationManager = CLLocationManager()
let geoCoder = CLGeocoder()
@Published var location: CLLocation? = nil
@Published var placemark: CLPlacemark? = nil
override init() {
super.init()
self.locationManager.delegate = self
self.locationManager.desiredAccuracy = kCLLocationAccuracyBest
self.locationManager.distanceFilter = kCLDistanceFilterNone
self.locationManager.requestWhenInUseAuthorization()
self.locationManager.startUpdatingLocation()

}
func geoCode(with location: CLLocation) {
geoCoder.reverseGeocodeLocation(location) { (placemark, error) in
if error != nil {
print(error!.localizedDescription)
} else {
self.placemark = placemark?.first
}
}
}
func startUpdating() {
self.locationManager.delegate = self
self.locationManager.requestWhenInUseAuthorization()
self.locationManager.startUpdatingLocation()
}
}
extension LocationManager: CLLocationManagerDelegate {
func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
guard let location = locations.first else {
return
}
self.location = location
self.geoCode(with: location)
}
}

ExploreView(发射时显示的第一个视图(

import SwiftUI
import CoreLocation
import Foundation

struct ExploreView: View {
@ObservedObject  var location = LocationManager()
@ObservedObject var fetcher: RestaurantFetcher

init() {
let location = LocationManager()
self.location = location
self.fetcher = RestaurantFetcher(locationManager: location)
self.location.startUpdating()
}
var body: some View {
ScrollView (.vertical) {
VStack {
HStack {
Text("Discover ")
.font(.system(size: 28))
.fontWeight(.bold)
+  Text(" (location.placemark?.locality ?? "")")
.font(.system(size: 28))
.fontWeight(.bold)
Spacer()                       
}
HStack {
SearchBar(text: .constant(""))
}.padding(.top, 16)                
HStack {
Text("Featured Restaurants")
.font(.system(size: 24))
.fontWeight(.bold)
Spacer()                       
NavigationLink(
destination: FeaturedView(),
label: {
Text("View All")
})                        
}.padding(.vertical, 30)                 
HStack {
Text("All Cuisines")
.font(.system(size: 24))
.fontWeight(.bold)
Spacer()
}                
Spacer()
}.padding()
}      
}
}
public class RestaurantFetcher: ObservableObject {
@Published var businesses = [RestaurantResponse]()
@ObservedObject var locationManager: LocationManager
let location = LocationManager()
var lat: String {
return "(location.location?.coordinate.latitude ?? 0.0)"
}
var long: String {
return "(location.location?.coordinate.longitude ?? 0.0)"
}
init(locationManager: LocationManager) {
let location = LocationManager()
self.locationManager = location
self.location.startUpdating()

load()
}
func load() {
print("(location.location?.coordinate.latitude ?? 0.0)")
print("user latitude top of function")
//Returns default values of 0.0
let apikey = "APIKEY Here"
let url = URL(string: "https://api.yelp.com/v3/businesses/search?latitude=(lat)&longitude=(long)&radius=40000")!
var request = URLRequest(url: url)
request.setValue("Bearer (apikey)", forHTTPHeaderField: "Authorization")
request.httpMethod = "GET"

URLSession.shared.dataTask(with: request) { (data, response, error) in
do {
if let d = data {
print("(self.location.location?.coordinate.longitude ?? 0.0)")
let decodedLists = try JSONDecoder().decode(BusinessesResponse.self, from: d)

// Returns actual location coordinates
DispatchQueue.main.async {
self.businesses = decodedLists.restaurants
}
} else {
print("No Data")
}
} catch {
print ("Caught")
}
}.resume()
}
}

Answer 1

尝试以下修改后的代码(我需要进行一些复制，所以请注意——可能会出现一些拼写错误(。

主要思想是订阅LocationManager更新的位置发布器，以侦听位置的显式更改，并仅在位置真正更新而不是零之后执行下一次API加载。

struct ExploreView: View {
@ObservedObject  var location: LocationManager
@ObservedObject var fetcher: RestaurantFetcher

init() {
let location = LocationManager()  // << use only one instance
self.location = location
self.fetcher = RestaurantFetcher(locationManager: location)

self.location.startUpdating()   // << do this only once
}

var body: some View {
ScrollView (.vertical) {
VStack {
HStack {
Text("Discover ")
.font(.system(size: 28))
.fontWeight(.bold)
+  Text(" (location.placemark?.locality ?? "")")
.font(.system(size: 28))
.fontWeight(.bold)
Spacer()
}
HStack {
SearchBar(text: .constant(""))
}.padding(.top, 16)
HStack {
Text("Featured Restaurants")
.font(.system(size: 24))
.fontWeight(.bold)
Spacer()
NavigationLink(
destination: FeaturedView(),
label: {
Text("View All")
})
}.padding(.vertical, 30)
HStack {
Text("All Cuisines")
.font(.system(size: 24))
.fontWeight(.bold)
Spacer()
}
Spacer()
}.padding()
}
}
}
import Combine
public class RestaurantFetcher: ObservableObject {
@Published var businesses = [RestaurantResponse]()
private var locationManager: LocationManager

var lat: String {
return "(locationManager.location?.coordinate.latitude ?? 0.0)"
}

var long: String {
return "(locationManager.location?.coordinate.longitude ?? 0.0)"
}

private var subscriber: AnyCancellable?
init(locationManager: LocationManager) {
self.locationManager = locationManager

// listen for available location explicitly
subscriber = locationManager.$location
.debounce(for: 5, scheduler: DispatchQueue.main) // wait for 5 sec to avoid often reload
.receive(on: DispatchQueue.main)
.sink { [weak self] location in
guard location != nil else { return }
self?.load()
}
}

func load() {
print("(locationManager.location?.coordinate.latitude ?? 0.0)")
print("user latitude top of function")
//Returns default values of 0.0
let apikey = "APIKEY Here"
let url = URL(string: "https://api.yelp.com/v3/businesses/search?latitude=(lat)&longitude=(long)&radius=40000")!
var request = URLRequest(url: url)
request.setValue("Bearer (apikey)", forHTTPHeaderField: "Authorization")
request.httpMethod = "GET"

URLSession.shared.dataTask(with: request) { (data, response, error) in
do {
if let d = data {
print("(self.locationManager.location?.coordinate.longitude ?? 0.0)")
let decodedLists = try JSONDecoder().decode(BusinessesResponse.self, from: d)

// Returns actual location coordinates
DispatchQueue.main.async {
self.businesses = decodedLists.restaurants
}
} else {
print("No Data")
}
} catch {
print ("Caught")
}
}.resume()
}
}