SwiftUI/组合监听 ObservableObject 中的多个发布者

Question

我有一个ObservableObject，里面还有两个ObservableObjects。这两个ObservableObject 中的每一个在内部都有一个或多个@Published 属性。我的解决方案有效，但我 100% 确定必须有另一种方法。我必须复制/粘贴所有内容才能使其正常工作。我尝试了两个将这两个发布者放在视图中，但是我需要将很多参数传递给子视图。有什么想法可以简化吗？

class PackageService: ObservableObject {
    @Published var package: Package
    @Published var error: Error?
    
    @Published var distance: Double?
    @Published var expectedTravelTime: String?
    
    @Published var amount: Int = 0
    @Published var cost: Double = 0
    
    @Published var annotations = [MKPointAnnotation]()

    @Published var isCalculating = true
    @Published var route: MKRoute?
    
    var amountService = AmountService()
    var routeService = RouteService()
    
    private var cancellables = Set<AnyCancellable>()
    
    init(package: Package) {
        self.package = package
        routeService.calcDirections(source: package.source.toCLLocationCoordinate2D, destination: package.destination.toCLLocationCoordinate2D)
        
        routeService.$route.sink { [self] route in
            self.route = route
            
            amountService.calc(distance: route?.distance)
            calc(route: route)
        }
        .store(in: &cancellables)
        
        routeService.$isCalculating.sink { [self] isCalculating in
            self.isCalculating = isCalculating
        }
        .store(in: &cancellables)
        
        
        routeService.$error.sink { [self] error in
            self.error = error
        }
        .store(in: &cancellables)
        
        amountService.$amount.sink { [self] amount in
            self.amount = amount
        }
        .store(in: &cancellables)
        
        amountService.$cost.sink { [self] cost in
            self.cost = cost
        }
        .store(in: &cancellables)
        
        amountService.$error.sink { [self] error in
            self.error = error
        }
        .store(in: &cancellables)
    }

Answer 1

似乎PackageService 只是另外两个服务的薄包装。

使用计算属性而不是订阅和发布每个属性的更改是有意义的：

var isCalculating: Bool { routeService.isCalculating }

var amount: Int { amountService.amount }

// etc...

并订阅一次以通知视图的更改：

routeService.objectWillChange
            .merge(with: amountService.objectWillChange)
            .sink(receiveValue: self.objectWillChange.send)
            .store(in: &cancellables)

---

另外，考虑将各种属性打包在一个数据模型中，例如：

struct AmountModel {
   var amount: Int
   var cost: Double
}

并让AmountService 拥有一个属性。这可以是 Result<AmountModel, Error> 来捕获数据或错误，或者，如果需要，可以将 Error 作为属性包含在内。