SwiftUI Tips

import SwiftUI

struct DemoModel {
    var title: String = "Demo Title"
}

class DemoViewModel: ObservableObject {
    @Published var model: DemoModel = DemoModel()
}

struct DemoView: View {
    /// 视图的声明周期内，SwiftUI 不会创建新实例 viewModel，viewModel 的生命周期被自动管理。
    @StateObject private var viewModel: DemoViewModel = DemoViewModel()
    var body: some View {
        Text(viewModel.model.title)
    }
}

#Preview {
    DemoView()
}

import SwiftUI

struct DemoModel {
    var title: String = "Demo Title"
}

class DemoViewModel: ObservableObject {
    @Published var model: DemoModel = DemoModel()
}

struct DemoView: View {
    /// 视图不拥有对象，只是引用和观察外部提供的对象
    @ObservedObject private var viewModel: DemoViewModel

    init(viewModel: DemoViewModel) {
        self.viewModel = viewModel
    }

    var body: some View {
        Text(viewModel.model.title)
    }
}

#Preview {
    let viewModel = DemoViewModel()
    return DemoView(viewModel: viewModel)
    /// 在 Xcode 中是不需要 return 显式返回值的
}