我正在结合两个发布者来确定地图视图的中心坐标应该是什么。这两家出版商是：
- 用户的初始位置由 a 确定（开始发送位置更新
CLLocationManager后报告的第一个位置）。CLLocationManager - 如果点击“当前位置的中心地图”按钮，用户的当前位置。
在代码中：
class LocationManager: NSObject, ObservableObject {
// The first location reported by the CLLocationManager.
@Published var initialUserCoordinate: CLLocationCoordinate2D?
// The latest location reported by the CLLocationManager.
@Published var currentUserCoordinate: CLLocationCoordinate2D?
// What the current map view center should be.
@Published var coordinate: CLLocationCoordinate2D = CLLocationCoordinate2D(latitude: 42.35843, longitude: -71.05977) // Default coordinate.
// A subject whose `send(_:)` method is being called elsewhere every time the user presses a button to center the map on the user's location.
var centerButtonTappedPublisher: PassthroughSubject<Bool, Never> = PassthroughSubject<Bool, Never>()
// The combined publisher that is where all my troubles lie.
var coordinatePublisher: AnyPublisher<CLLocationCoordinate2D, Never> {
Publishers.CombineLatest($initialUserCoordinate, centerButtonTappedPublisher)
.map { initialCoord, centerButtonTapped in
var latestCoord = initialCoord
if centerButtonTapped {
latestCoord = self.currentUserCoordinate
}
return latestCoord
}
.replaceNil(with: CLLocationCoordinate2D(latitude: 42.35843, longitude: -71.05977))
.eraseToAnyPublisher()
}
private var cancellableSet: Set<AnyCancellable> = []
//... Other irrelevant properties
private override init() {
super.init()
coordinatePublisher
.receive(on: RunLoop.main)
.assign(to: \.coordinate, on: self)
.store(in: &cancellableSet)
//... CLLocationManager set-up
}
}
extension LocationManager: CLLocationManagerDelegate {
//...
func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
// We are only interested in the user's most recent location.
guard let location = locations.last else { return }
let latestCoord = location.coordinate
if initialUserCoordinate == nil {
initialUserCoordinate = latestCoord
}
currentUserCoordinate = latestCoord
}
//...
}
出版商$initialUserCoordinate和都centerButtonTappedPublisher发布更新 - 我已经确认了这一点。但是，coordinatePublisher只有在点击“当前位置的中心地图”按钮时才会触发组合发布者。initialUserCoordinate首次设置属性时它永远不会触发。
这个问题建议在.receive(on: RunLoop.main)之后添加一个，Publishers.CombineLatest($initialUserCoordinate, centerButtonTappedPublisher)但这对我不起作用。
我究竟做错了什么？