SwiftUI can't use navigationBarTitle modifier (deprecated) in iOS 13 versions, but can in iOS 14

Question

I lowered my minimum deployment target from iOS 14.0 to iOS 13.0. I then got this error:

'navigationBarTitle(_:displayMode:)' is only available in iOS 14.0 or newer

But, the documentation says it's available from iOS 13.0-14.2, and previous SO answers posted (back when iOS 13 was the newest) also used it.

Is it because it's "Deprecated" that I can't use it? But then why can I use it in iOS 14.0?

---

Edit:

After trying to reproduce, it seems to work only if I don't have title stored in a property.

import SwiftUI

struct ContentView: View {
    var body: some View {
        Text("Hi!")
            .navigationBarTitle("Title", displayMode: .inline)
    }
}
struct DetailView: View {
    var title: String = ""
    var body: some View {
        Text("Hi!")
            .navigationBarTitle(title, displayMode: .inline)
    }
}

Answer 1

If you look closely at what the navigationBarTitle call resolves to, it isn't the method you linked:

func navigationBarTitle(_ title: Text, displayMode: NavigationBarItem.TitleDisplayMode) -> some View

It is:

func navigationBarTitle<S>(_ title: S, displayMode: NavigationBarItem.TitleDisplayMode) -> some View where S : StringProtocol

It can't resolve to the first one because you are not passing a Text as the title, are you? You declared the argument title to be a String.

Here's the documentation for the second method. From the documentation we can clearly see that it is available from iOS 14.0 to 14.2.

The reason why using a string literal as the title works (such as in ContentView) is because you are calling yet another overload of navigationBarTitle:

func navigationBarTitle(_ titleKey: LocalizedStringKey, displayMode: NavigationBarItem.TitleDisplayMode) -> some View

LocalizedStringKey conforms to ExpressibleByStringLiteral, so string literals can be passed to an argument of type LocalizedStringKey, but not a variable like title.

Answer 2

Its because you are using a string for your title instead of a Text view.

I ran into this same issue as you.

Basically in iOS 14 they added the ability to just drop a string into your nav bar directly. Prior to that you had to use .navigationBarTitle(Text(yourString), displayMode: .inline)