Question

下面是所有相关文件，这是用于开发swiftui项目的MVVM模式。

// ContentView.swift

import SwiftUI

struct ContentView: View {
    @ObservedObject var vm: ViewModel
    
    var body: some View {
        Rectangle().fill(Color.yellow).frame(width: 200, height: CGFloat(vm.model.height))
        Button("animate") {
                self.vm.changeHeight()
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView(vm: ViewModel())
    }
}

// model.swift
import SwiftUI
import Foundation


struct Model {
    var height = 100
    var width = 100
    
    mutating func changeHeight() {
        withAnimation {
            height = 300
        }
    }
}

//ViewModel.swift
import Foundation

class ViewModel: ObservableObject {
    @Published var model = Model()

    func changeHeight() {
        model.changeHeight()
    }
}

单击按钮后，高度将立即更改，而不会显示动画。如果我在viewModel或view中使用withAnimation，那么更改会被动画化，为什么？

swiftui的withAnimation如何工作？

0 个答案: