Swift and C++ In The Same Project

Question

dpm OP

Created Jan ’24

Replies 3

Boosts 0

Views 1.4k

Participants 4

Hi --

I am attempting to use C++ and Swift in a single project but I am struggling with finding the proper way to do this. Ideally I want to have both my C++ and Swift code in the same project and not use a framework to keep them separate.

As an example, how would I create an object of the following C++ class:

class Foo {
  public:
    Foo() {
      // do stuff
    }
}

From what I read, it should be as simple as this:

let foo = Foo()

But Xcode says it Cannot find 'Foo' in scope. How do I import Foo into my Swift code? Is there a project setting that needs to be changed to automatically make my C++ classes available? Or do I need to create a Clang module (as described in this page: https://www.swift.org/documentation/cxx-interop/#importing-c-into-swift) to expose the C++ code to Swift? If so, where in my Xcode project should that go?

I am using Xcode 15.2 on macOS 14.2.1. I have also set the C++ and Objective-C Interoperability setting for my project to C++/Objective-C++.

Answered by DTS Engineer in 776551022

do I need to create a Clang module … to expose the C++ code to Swift?

No. While it’s likely that you will want to do that once you get deep into this, it’s possible to use C++ interoperability with a bridging header. Try this:

Using Xcode 15.2, create a new test project from the macOS > Command Line Tool template.
Set the C++ and Objective-C Interoperability build setting to C++ and Objective-C interoperability (objcxx).
Choose New > File and add a C++ file to your project. I called it Waffle.
Xcode will ask you whether you want to create a bridging header. Agree to that.
Add this to that bridging header:
```
#include "Waffle.hpp"
```

Edit Waffle.hpp to look like this:

#ifndef Waffle_hpp
#define Waffle_hpp

class Waffle {
public:
    Waffle() { }
    void varnish();
};

#endif

And Waffle.cpp to look like this:

#include "Waffle.hpp"

#include <iostream>

void Waffle::varnish() {
    std::cout << "Hello Cruel World!\n";
}

Finally, edit main.swift to look like this:

import Foundation

func main() {
    var w = Waffle()
    w.varnish()
}

main()

Choose Product > Run. The program prints:
```
Hello Cruel World!
```

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

Boost

Answer 1

DTS Engineer OP

Apple

Jan ’24

Accepted Answer

do I need to create a Clang module … to expose the C++ code to Swift?

No. While it’s likely that you will want to do that once you get deep into this, it’s possible to use C++ interoperability with a bridging header. Try this:

Using Xcode 15.2, create a new test project from the macOS > Command Line Tool template.
Set the C++ and Objective-C Interoperability build setting to C++ and Objective-C interoperability (objcxx).
Choose New > File and add a C++ file to your project. I called it Waffle.
Xcode will ask you whether you want to create a bridging header. Agree to that.
Add this to that bridging header:
```
#include "Waffle.hpp"
```

Edit Waffle.hpp to look like this:

#ifndef Waffle_hpp
#define Waffle_hpp

class Waffle {
public:
    Waffle() { }
    void varnish();
};

#endif

And Waffle.cpp to look like this:

#include "Waffle.hpp"

#include <iostream>

void Waffle::varnish() {
    std::cout << "Hello Cruel World!\n";
}

Finally, edit main.swift to look like this:

import Foundation

func main() {
    var w = Waffle()
    w.varnish()
}

main()

Choose Product > Run. The program prints:
```
Hello Cruel World!
```

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

2

Answer 2

dpm OP

Jan ’24

Thank you -- that was exactly what I needed to do.

0

Answer 3

DTS Engineer OP

Apple

May ’24

As we know we cannot have bridging header for a framework then how can I make these C++ files available to swift?

It’s probably best to start a new thread for this. Use the same tags as this thread so that I see it.

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

0