Find which button is pressed in a Grid in SwiftUI

Question

Created Feb ’21

Replies 8

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Hello,

I'm trying to create sort of a menu view where buttons are paid out in a grid. Each menu button consists of an icon and a title. And I have multiple menus like this throughout the app.

So I decided to create a reusable button view like this.

Code Block swiftstruct MenuButton: View {
    let title: String
    let icon: Image
    var action: () -> Void
    var body: some View {
        Button(action: {
            action()
        }) {
            VStack {
                icon
                    .resizable()
                    .aspectRatio(contentMode: .fit)
                    .frame(minWidth: 40, idealWidth: 50, maxWidth: 60, minHeight: 40, idealHeight: 50, maxHeight: 60)
                    .padding(.bottom, 3)
                Text(title)
                    .foregroundColor(.black)
                    .font(.system(size: 15, weight: .bold))
                    .multilineTextAlignment(.center)
                    .minimumScaleFactor(0.7)
                    .lineLimit(2)
            }
            .padding(10)
        }
        .frame(maxWidth: .infinity, maxHeight: .infinity)
        .aspectRatio(1, contentMode: .fill)
        .overlay(RoundedRectangle(cornerRadius: 10).stroke(Color.blue, lineWidth: 0.6))
    }
}

To keep the Menus organised, I opted to use an enum.

Code Block swiftenum Menu {
    enum UserType: CaseIterable, CustomStringConvertible {
        case new
        case existing
        var description: String {
            switch self {
            case .new:
                return "New User"
            case .existing:
                return "Existing User"
            }
        }
        var icon: String {
            switch self {
            case .new:
                return "new_user"
            case .existing:
                return "existing_user"
            }
        }
    }
    enum Main: CaseIterable, CustomStringConvertible {
        case create
        case search
        case notifications
        var description: String {
            switch self {
            case .create:
                return "Create"
            case .search:
                return "Search"
            case .notifications:
                return "Notifications"
            }
        }
        var icon: String {
            switch self {
            case .create:
                return "create"
            case .search:
                return "search"
            case .notifications:
                return "notifications"
            }
        }
    }
}

And I display he menu grid like so.

Code Block swiftstruct ContentView: View {
    private let columns = [
        GridItem(.flexible(), spacing: 20),
        GridItem(.flexible(), spacing: 20)
    ]
    var body: some View {
        ScrollView {
            LazyVGrid(columns: columns, spacing: 20) {
                ForEach(Menu.UserType.allCases, id: \.self) { item in
                    MenuButton(title: item.description, icon: Image(item.icon), action: {})
                }
            }
            .padding(.horizontal)
            .padding([.top, .bottom], 20)
        }
    }
}

So far so good. The menu displays properly. But this is where I've hit a snag. I can't figure out a way to find which button user taps on.

I could include the menu type inside the MenuButton view itself and pass it back in the button tap closure.

Code Block swiftstruct MenuButton: View {
    let item: Menu.UserType
    var action: (_ item: Menu.UserType) -> Void
    
    var body: some View {
        Button(action: {
            action(item)
        }) {
            // ...
        }
        // ...
    }
}

But this makes the MenuButton view couple of one menu type and not reusable.

So I was wondering if there's another, better way to handle this. Any suggestions, ideas would be appreciated.

Thanks.

Answered by OOPer in 662610022

But it's giving me the following error.

In Swift, nested type does not work as a constraining something, but is just a namespace.

If you want to put some constraint for the generic argument, you may need to introduce another protocol:

Code Block protocol MenuItem {}
extension Menu.UserType: MenuItem {}
extension Menu.Main: MenuItem {}
struct MenuButton<ItemType: MenuItem>: View {
    //...
}

Boost

Answer 1

OOPer OP

Feb ’21

But this makes the MenuButton view couple of one menu type and not reusable.

Why don't you make your MenuButton generic?

Code Block struct MenuButton<ItemType>: View {
    let item: ItemType
    //...
    var action: (ItemType) -> Void
    var body: some View {
        Button(action: {
            action(item)
        }) {
            //...
        }
        //...
    }
}

0

Answer 2

isuru_cenango OP

Feb ’21

Thanks for the response @OOPer.

I'm struggling to figure out how to incorporate generics with how I've created my objects, enums inside enums. Would it still work in my case?

I tried this.

Code Block swiftstruct MenuButton<T: Menu>: View {
}

But it's giving me the following error.

Type 'T' constrained to non-protocol, non-class type 'Menu'

0

Answer 3

OOPer OP

Feb ’21

Accepted Answer

But it's giving me the following error.

In Swift, nested type does not work as a constraining something, but is just a namespace.

If you want to put some constraint for the generic argument, you may need to introduce another protocol:

Code Block protocol MenuItem {}
extension Menu.UserType: MenuItem {}
extension Menu.Main: MenuItem {}
struct MenuButton<ItemType: MenuItem>: View {
    //...
}

1

Answer 4

isuru_cenango OP

Feb ’21

Thanks a lot @OOPer. Made some good progress thanks to your guidance. One last question if I may.

So I made a MenuItem protocol, made the sub-enums under Menu conform to it, made the MenuButton accept it as a generic parameter.

Code Block swift/* MenuItem */
protocol MenuItem {
    var title: String { get }
    var image: String { get }
}
/* Menu */
enum Menu {
	enum UserType: CaseIterable, MenuItem {
        case new
        case existing
        
        var title: String {
            / / ..
        }
        
        var image: String {
            / / ..
        }
    }
}
/* MenuViewObservable */
class MenuViewObservable: ObservableObject {
    var onButtonTap: ((MenuItem) -> Void)!
}
/* UserTypeMenuView */
struct UserTypeMenuView: View {
    @ObservedObject var observable: MenuViewObservable
    
    / / ..
    
    var body: some View {
        ScrollView {
            LazyVGrid(columns: columns) {
                ForEach(Menu.UserType.allCases, id: \.self) { item in
                    MenuButton<Menu.UserType>(item: item, action: observable.onButtonTap)
                }
            }
        }
    }
}
/* MenuButton */
struct MenuButton<T: MenuItem>: View {
    let item: T
    var action: (T) -> Void
    
    var body: some View {
        Button(action: {
            action(item)
        }) {
            / / ..
        }
    }
}

Everything works great. Now I can get the title of the menu from where I'm subscribing to the closure.

Code Block swiftobservable.onButtonTap = { item in
    print(item.title)
}

Is there a way to actually get the type of the enum here? So I can do something like this.

Code Block swiftobservable.onButtonTap = { item in
    switch item {
    case .new:
        / / ..
    case .existing:
        / / ..
    }
}

When I print out the type of it like this print(type(of: item)), I see the UserType in the console. But I can't access it.

0

Answer 5

OOPer OP

Feb ’21

Is there a way to actually get the type of the enum here? So I can do something like this.

Unfortunately, with declaring var onButtonTap: ((MenuItem) -> Void)!, you are disposing the type info to tell to Swift compiler.
(By the way, you should not use implicitly unwrapped Optional here. Better use explicit Optional or non-Optional.)

You can make MenuViewObservable generic:

Code Block class MenuViewObservable<ItemType: MenuItem>: ObservableObject {
    var onButtonTap: ((ItemType) -> Void) = {_ in}
}

But this may or may not work depending on the actual usage of observable.

1

Answer 6

isuru_cenango OP

Feb ’21

Oh I see. That's unfortunate but I can work around it by comparing the title property values. Thanks a ton for all your help.

btw I changed the ObservableObjects to use generics. It doesn't seem to have an effect on functionality-wise. Everything works ok.

However (this issue actually persisted before changing it to generics too), the SwiftUI preview for this view doesn't get rendered.

Code Block swiftclass MenuViewObservable<T: MenuItem>: ObservableObject {
    var onButtonTap: ((MenuItem) -> Void) = { _ in }
}
struct UserTypeMenuView: View {
    @ObservedObject var observable: MenuViewObservable<Menu.UserType>
    
    private let columns = [
        GridItem(.flexible(), spacing: 20),
        GridItem(.flexible(), spacing: 20)
    ]
    
    var body: some View {
        ScrollView {
            LazyVGrid(columns: columns, spacing: 20) {
                ForEach(Menu.UserType.allCases, id: \.self) { item in
                    MenuButton<Menu.UserType>(item: item, action: observable.onButtonTap)
                }
            }
            .padding(.horizontal)
            .padding([.top, .bottom], 20)
        }
    }
}
struct UserTypeMenuView_Previews: PreviewProvider {
    static var previews: some View {
        UserTypeMenuView(observable: MenuViewObservable<Menu.UserType>())
    }
}

Shows the following error.

'Menu' is ambiguous for type lookup in this context

0

Answer 7

OOPer OP

Feb ’21

btw I changed the ObservableObjects to use generics. It doesn't seem to have an effect on functionality-wise.

When you make MenuViewObservable generic, better use the generic type as the argument type of the closure:

Code Block class MenuViewObservable<T: MenuItem>: ObservableObject {
    var onButtonTap: ((T) -> Void) = { _ in } //<- Use `T`, not `MenuItem`
}

Shows the following error.

I cannot reproduce the same error with your currently shown code. Something hidden in your project may be affecting.
For example, don't you have another Menu type in you project, including imported modules?

0

Answer 8

isuru_cenango OP

Feb ’21

For example, don't you have another Menu type in you project, including imported modules?

This is a brand new project I'm working on and I'm still creating the UIs. So no other modules/third-party frameworks or anything added yet. And no other objects named Menu either. Very strange. I'm going to replicate this menu part only on another project and see what happens.

0