Create a Toggle to prefix text to a Text Input field

[ErikLa]

I am creating an App that will create Sites based on the information input into the App. The first Input Text field will be the Site Name field. Further down the App will be a Toggle input (to allow or not allow external users) that if selected would need to append "External - " into the first Input Text field for the name of the site. One caveat to this scenario is that the appended text needs to be uneditable so that the user doesn't try to bypass the naming convention for External capable sites.

So far This is what I've done.

I have a Text Input field: "InputSiteName" 

The "Default" setting is set to "EXT_Toggle & " " "

I have a Toggle input: "ToggleExternal"

The "OnCheck" value is set to "UpdateContext({EXT_Toggle: "External -"})"

The "OnUncheck" value is set to "UpdateContext({EXT_Toggle: ""})"

This works to add the "External - " into the Name field but it removes the previous text and does not append it. How can I get this to append to whatever text is already in the name input field?

[BrianS]

It seems like that default would ignore the text input.

I think the default should be something like "EXT_Toggle & ThisItem.InputSiteName"

that will add the toggle value to the user input without showing that value to the user

[ErikLa · Accepted solution]

I found solutions to my issues by using a Substitute and adding a readolny flag to the startup of the app.

These were modifications I used on the OnUncheck for the Toggle switch.

UpdateContext({EXT_Toggle: Substitute( "External - " & InputSiteName.Text, "External - ", "")});
Set(readOnlyFields,false);