How to print() to Xcode console in SwiftUI?

Question

So I tried to put a print statement while debugging in a SwiftUI View.

print(\"landmark: \\(landmark)\")

In the following body.

<         


        

Answer 1

At least in Xcode 12/Swift 5.3, you can easily add a print statement anywhere in a function builder by simply storing its return value in a wildcard, effectively ignoring it:

let _ = print("hi!")

No setup or other verbosity needed!

Answer 2

You can not print in body structure i.e. a structure which is some view type.For print you need to make function out of body structure and call it using button or something else.

Answer 3

You can't because you're in a computed property. You need for example a button and in the action you define the print. Or work with breakpoints

Answer 4

Here's a helper Print( ... ) View that acts like a print( ... ) function but within a View

Put this in any of your view files

extension View {
    func Print(_ vars: Any...) -> some View {
        for v in vars { print(v) }
        return EmptyView()
    }
}

and use inside of body like so

Print("Here I am", varOne, varTwo ...)

or inside a ForEach {} like so

self.Print("Inside ForEach", varOne, varTwo ...)

Note: you might need to put Print() into a Group {} when combining with existing views

Answer 5

Try right-clicking on the live preview play button and selecting 'Debug Preview from the popup

Answer 6

It is possible to use print() remembering that all SwiftUI View content are (a) implicit closures and (b) it is highly recommended to decompose views as much as possible to have simple structure, so it might look like the following...

struct Model: Identifiable {
    let value: String
    var id: String {
        value
    }
    init (_ value: String) {
        self.value = value
    }
}

struct TestView: View {
    @State var showFavoritesOnly = false
    @State var listData: [Model] = [Model("one"), Model("two"), Model("three")]

    var body: some View {
        NavigationView {
            List {
                Toggle(isOn: $showFavoritesOnly) {
                    Text("Favorite only")
                }
                ForEach(listData) { data in
                    self.rowView(data: data)
                }
            }
        }
    }

    private func rowView(data: Model) -> some View {
#if DEBUG
        print(">> \(data.value)")
#endif
        return NavigationLink(destination: Text("Details")) {
            Text("Go next from \(data.value)")
        }
    }
}

... and right clicking in Preview to select run as Debug Preview we get:

2019-10-31 14:28:03.467635+0200 Test[65344:11155167] [Agent] Received connection, creating agent
2019-10-31 14:28:04.472314+0200 Test[65344:11155168] [Agent] Received display message
>> one
>> two
>> three