I have a SwiftUI project using MVVM structure but I have lots of variables in View now, is that right?How can I improve this?

For example, this is my add record view

    @State private var money: String = ""
    @State private var desc: String = ""
    @FocusState var isDescFieldFocused: Bool
    @State private var showDatePicker: Bool = false
    @State private var showingAlert: Bool = false
    @State private var showConstantlyAlert: Bool = false
    @State private var showKeyPad: Bool = false
    @State private var showCatesPanel: Bool = false
    @State private var selectedCate: String = ""

Should I put all these in View Models?

CodePudding user response：

Like you said, you could create a view model for that view, which would either be a @StateObject or @ObservedObject (depends on whether you want to create the view model within the view or inject it from outside).

I tend to create view models for my views if they require any logic and not only display information which is passed down from parent views.

Thus, you could do this:

final class YourNameViewModel: ObservableObject {

    @Published var money = ""
    // other properties

    init() {
        ...
    }

}

and use it within your view like so:

struct YourNameView: View {

     @StateObject var vm = YourNameViewModel()
     // or @ObservedObject var vm: YourNameViewModel (if you want to pass it down from a parent view)    

}

CodePudding user response：

Apple addresses this in Data Essentials in SwiftUI WWDC 2020 at 4:18

EditorConfig can maintain invariants on its properties and be tested independently. And because EditorConfig is a value type, any change to a property of EditorConfig, like its progress, is visible as a change to EditorConfig itself. 4:18

So in your case it would look like:

struct MyConfig {
    var money: String = ""
    var desc: String = ""
    var showDatePicker: Bool = false
    var showingAlert: Bool = false
    var showConstantlyAlert: Bool = false
    var showKeyPad: Bool = false
    var showCatesPanel: Bool = false
    var selectedCate: String = ""

    mutating func otherLogic() {}
}

struct MyView {

    @State var config = MyConfig()
    @FocusState var isDescFieldFocused: Bool

Just to let you know, MVVM (i.e. using objects for view data) is not suitable for SwiftUI because the View struct and property wrappers is equivalent to a view model object but faster and less error-prone. If you use actual objects instead of learning SwiftUI's features you'll have problems.

The time we use an ObservableObject in SwiftUI is for model data, i.e. the environment object/singleton that stores the arrays of model structs in @Published properties and is responsible for loading/saving/syncing etc. the model data etc. That is covered in the same video later on, from about 9mins 30secs.

For write-access to model data we use @Binding.

We used to also use @StateObject for handling networking or delegates but that is pretty much redundant now we have the task modifier which does the same thing but better.