Swift 5 version and CPP interoperability in Qt application. How?

[bogong]

Hello all!

Got success in implementing Swift-CPP interoperability in plain CMake project https://youtu.be/mUpvDT03cw8 For now trying to implement the same functionality in Qt/QML application for iOS. Got few questions.

First question.
By default in Qt 6 application with CMake, when added Swift language to project by something like this:

project(${A_NAME_TARGET} VERSION 0.1 LANGUAGES CXX Swift)

The Swift version is 4.0 in automatically generated XCode project. Why so? If it will be changed on 5.0 or higher will it be affecting Qt application itself?

Second question.
Is the difference for Qt/QML application when using Ninja or XCode for building application in case of using Swift? When in principal do better to use XCode and when do better Ninja? By default in Qt Creator using Ninja, why?