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How to Delete List rows from SwiftUI List

 2 years ago
source link: https://sarunw.com/posts/swiftui-list-ondelete/
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How to Delete List rows from SwiftUI List

01 Dec 2022 ⋅ 4 min read ⋅ SwiftUI List

Table of Contents

SwiftUI List has many built-in features equipped. The way we enable these features is by attach a view modifier in a view hierarchy.

The view modifier that enable the delete function is onDelete(perform:).

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How to Delete List rows from SwiftUI List

To enable the delete function in SwiftUI List, you need to do the following steps.

The onDelete modifier only works with ForEach, so you need to change how you populate your List view to use ForEach.

Create Data Source

Since you want to delete an item in a List view, your data source must be mutable.

I use a @State variable as a data source in this example.

@State private var contacts = [
    "John",
    "Alice",
    "Bob",
    "Foo",
    "Bar"
]

Create a List view with ForEach

The onDelete modifier only works with ForEach, so we need to populate our List view using ForEach.

struct ContentView: View {
    @State private var contacts = [
        "John",
        "Alice",
        "Bob",
        "Foo",
        "Bar"
    ]

var body: some View {
        List {
            ForEach(contacts, id: \.self) { contact in
                Text(contact)
            }
        }
    }
}

Apply onDelete modifier on ForEach

Apply onDelete modifier on ForEach to enable the delete function.

struct ContentView: View {
    @State private var contacts = [
        "John",
        "Alice",
        "Bob",
        "Foo",
        "Bar"
    ]

var body: some View {
        List {
            ForEach(contacts, id: \.self) { contact in
                Text(contact)
            }.onDelete { indexSet in
                // TODO: delete items
            }
        }
    }
}

Delete items from the Data Source

The onDelete modifier doesn't automatically delete an item from your data source. You have to do it yourselves.

The onDelete perform action pass IndexSet as an argument. This is the set of indices of items about to be deleted.

.onDelete { deleteOffsets: IndexSet in

}

We use the passing indices to remove the item from our data source. Swift Array already has a remove(atOffsets:) method that takes an IndexSet as an argument.

struct ContentView: View {
    @State private var contacts = [
        "John",
        "Alice",
        "Bob",
        "Foo",
        "Bar"
    ]

var body: some View {
        List {
            ForEach(contacts, id: \.self) { contact in
                Text(contact)
            }.onDelete { indexSet in
                contacts.remove(atOffsets: indexSet)
            }
        }
    }
}

What does onDelete do

Adding an onDelete(perform:) modifier will enable the ability to delete items in that List view.

Users can delete the List item in two ways.

Swipe to delete

Users can swipe from right to left on any list row to delete that particular row.

Swipe to delete

Swipe to delete

Deleting items in EditMode

Another way to delete the list item is in the edit mode.

There are two options to enter the edit mode.

  1. Using the EditButton
  2. Setting the .editMode environment value

I will use EditButton in this case.

struct ContentView: View {
    @State private var contacts = [
        "John",
        "Alice",
        "Bob",
        "Foo",
        "Bar"
    ]

var body: some View {
        // 1
        NavigationView {
            List {
                ForEach(contacts, id: \.self) { contact in
                    Text(contact)
                }.onDelete { indexSet in
                    contacts.remove(atOffsets: indexSet)
                }
            }
            .toolbar {
                // 2
                EditButton()
            }
        }
    }
}

I wrap the List view inside NavigationView` 1 and add the Edit button there 2.

Once you enter the Edit mode by tapping the "Edit" button, you will see the delete button in front of each row.

Edit Mode.

Edit Mode.

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How to conditionally Disable the Delete ability

If you want to disable the delete ability based on some condition, you can do that by passing nil to the onDelete.

ForEach(contacts, id: \.self) { contact in
    Text(contact)
}
.onDelete(perform: nil)

Here is an example where we control reorder ability from the boolean value, enableDelete.

struct DeleteExample: View {
    @State private var contacts = [
        "John",
        "Alice",
        "Bob",
        "Foo",
        "Bar"
    ]

// 1
    @State private var enableDelete = true

var body: some View {
        NavigationView {
            List {
                Toggle("Enable Delete", isOn: $enableDelete)
                ForEach(contacts, id: \.self) { contact in
                    Text(contact)
                }
                // 2
                .onDelete(perform: enableDelete ? delete: nil)
            }
            .toolbar {
                EditButton()
            }
        }

}

// 3
    func delete(at offsets: IndexSet) {
        contacts.remove(atOffsets: offsets)
    }
}

1 A state variable use to control delete ability.
2 We use enableDelete to conditionally enable/disable the delete ability. We disable it by set perform closure as nil.
3 We extract a delete logic out as a separate function to improve readability.

Disable the delete ability by passing nil to the onDelete.

Disable the delete ability by passing nil to the onDelete.


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