Type mismatch between SwiftUI textFieldStyle modifiers RoundedBorderTextFieldStyle and PlainTextFieldStyle

Question

I'm attempting to change the .textFieldStyle modifier for a TextField based upon whether my View is editing. I declare var isEditing: Bool, set this in the parent View and check against this in the body. My code:

TextField("Type a Name", text: $name) {
    myManagedObjectObserved.attribute = name
}
.textFieldStyle(isEditing ? RoundedBorderTextFieldStyle() : PlainTextFieldStyle())

The compiler complains with the following build time error...

Result values in '? :' expression have mismatching types 'RoundedBorderTextFieldStyle' and 'PlainTextFieldStyle'

Don't understand why? Is anyone able to explain please?

Answer 1

They are different types, so swift type checking reports error.

Here is possible solution (tested with Xcode 12)

@ViewBuilder
var body: some View {
    if isEditing {
        TextField("Type a Name", text: $name) {
            myManagedObjectObserved = name
        }
        .textFieldStyle(RoundedBorderTextFieldStyle())
    } else {
        TextField("Type a Name", text: $name) {
            myManagedObjectObserved = name
        }
        .textFieldStyle(PlainTextFieldStyle())
    }
}

Update: more convenient variant (with same idea)

extension TextField {
    @ViewBuilder
    func editingStyle(if flag: Bool) -> some View {
        if flag {
            self.textFieldStyle(RoundedBorderTextFieldStyle())
        } else {
            self.textFieldStyle(PlainTextFieldStyle())
        }
    }
}

struct TestView: View {
    @State private var name = ""
    @State private var isEditing = false

    @ViewBuilder
    var body: some View {
        TextField("Type a Name", text: $name) {
            myManagedObjectObserved = name
        }
        .editingStyle(if: isEditing)
    }
}