SwiftUI中如何控制ViewModel里@Published属性更新的API调用次数？

我有一个遵循ObservableObject协议的ViewModel类：

class AddPassaround : ObservableObject {
    @Published var name: String = ""
    @Published var reversed : String = ""
    @Published var password: String = ""
    @Published var age: String = ""
    @Published var address: String = ""
    @Published var oneAnotherProperty: String = ""

    init() {
    }
}

每当任一@Published属性更新时，我都会调用一个API。但当通过代码批量更新多个属性时（如下示例），会触发多次API调用和视图重绘：

viewModel.name = "test"
viewModel.password = "newPassword"
viewModel.oneAnotherProperty = "notUpdateAll"

如何在这种批量更新场景下让API只调用一次，同时保持单个属性更新时的正常行为？

方法1：手动控制变更通知与批量更新 #

给ViewModel添加一个批量更新方法，手动发送一次objectWillChange通知，一次性修改目标属性后统一调用API：

import Combine

class AddPassaround : ObservableObject {
    @Published var name: String = ""
    @Published var reversed : String = ""
    @Published var password: String = ""
    @Published var age: String = ""
    @Published var address: String = ""
    @Published var oneAnotherProperty: String = ""

    private var cancellables = Set<AnyCancellable>()
    
    init() {
        // 单个属性更新时自动触发API
        setupPropertySubscriptions()
    }
    
    private func setupPropertySubscriptions() {
        let propertyPublishers = [
            $name, $reversed, $password, $age, $address, $oneAnotherProperty
        ]
        
        Publishers.MergeMany(propertyPublishers)
            .sink { [weak self] _ in
                self?.callAPI()
            }
            .store(in: &cancellables)
    }
    
    // 批量更新专用方法
    func batchUpdate(name: String? = nil, password: String? = nil, oneAnotherProperty: String? = nil) {
        // 手动发送变更通知，合并视图更新
        objectWillChange.send()
        
        // 批量修改属性
        if let name = name { self.name = name }
        if let password = password { self.password = password }
        if let oneAnotherProperty = oneAnotherProperty { self.oneAnotherProperty = oneAnotherProperty }
        
        // 重置订阅并手动调用一次API
        cancellables.removeAll()
        setupPropertySubscriptions()
        callAPI()
    }
    
    private func callAPI() {
        // 你的API调用逻辑
    }
}

使用时直接调用批量方法：

viewModel.batchUpdate(name: "test", password: "newPassword", oneAnotherProperty: "notUpdateAll")

方法2：用标志位跳过批量更新时的重复API调用 #

给ViewModel加一个临时标志，批量更新时开启标志阻止属性变更触发API，完成后手动调用一次API并关闭标志：

import Combine

class AddPassaround : ObservableObject {
    @Published var name: String = ""
    @Published var reversed : String = ""
    @Published var password: String = ""
    @Published var age: String = ""
    @Published var address: String = ""
    @Published var oneAnotherProperty: String = ""

    private var isBatchUpdating = false
    private var cancellables = Set<AnyCancellable>()
    
    init() {
        setupPropertySubscriptions()
    }
    
    private func setupPropertySubscriptions() {
        let propertyPublishers = [
            $name, $reversed, $password, $age, $address, $oneAnotherProperty
        ]
        
        Publishers.MergeMany(propertyPublishers)
            .sink { [weak self] _ in
                guard let self = self else { return }
                // 批量更新时跳过API调用
                if !self.isBatchUpdating {
                    self.callAPI()
                }
            }
            .store(in: &cancellables)
    }
    
    func batchUpdate(name: String, password: String, oneAnotherProperty: String) {
        isBatchUpdating = true
        
        // 批量修改属性
        self.name = name
        self.password = password
        self.oneAnotherProperty = oneAnotherProperty
        
        isBatchUpdating = false
        // 批量完成后手动调用一次API
        callAPI()
    }
    
    private func callAPI() {
        // 你的API调用逻辑
    }
}

这种方法不修改原有订阅逻辑，单个属性更新时仍正常触发API，仅批量更新时合并调用。

方法3：利用withAnimation合并变更（极简方案） #

如果API调用是通过视图onChange或objectWillChange订阅触发的，可将批量更新代码放在withAnimation闭包里（无需实际动画），SwiftUI会自动合并所有变更为一次通知：

withAnimation {
    viewModel.name = "test"
    viewModel.password = "newPassword"
    viewModel.oneAnotherProperty = "notUpdateAll"
}

注意：若API是在属性didSet中调用的，此方法无效，因为didSet仍会在每次属性修改时执行。

内容的提问来源于stack exchange，提问作者arun siva