Basic c++xcodeproj call to swift code

I use Xcode 26. I like to use the modern mix from 2023 of c++ & swift. there is the fibonacci example that is swift app call to c++. here is the CppCallSwiftCommandLine check that fails:

I’m not sure what’s going on in your case, but I’ve been meaning to play around with C++ interoperability for a while so I sat down to test this today. I started out by testing the case where Swift calls C++:

1. In Xcode 26.0.1, I created a new project from the macOS > Command Line template, selecting Swift as the language.

2. I changed the C++ and Objective-C Interoperability build setting to C++ / Objective-C++.

3. I created a new file and its header from the macOS > C++ File template.

4. That asked me whether I want to create a bridging header, which I agreed to.

5. In that bridging header I added:

   #include "CppSide.hpp"
   

6. In CppSide.hpp I added a prototype of a function:

   extern int cppAdd(int a, int b);
   

   and in CppSide.cpp I added the implementation:

   extern int cppAdd(int a, int b) {
       return a + b;
   }
   

7. In main.swift, I added code to call that:

   let c = cppAdd(40, 2)
   print("Hello, World! \(42)")
   

8. I built and ran the tool. It printed:

   Hello, World! 42
   

Next I testing the other direction:

1. I created a new file from the macOS > Swift template.

2. I populated it like so:

   public class SwiftSide {
       public static func swiftAdd(_ a: CInt, _ b: CInt) -> CInt {
           return a + b
       }
   }
   

3. In CppSide.cpp, I added an include of the Swift header:

   #include "Test805433-Swift.h"
   

   then modified cppAdd(…) to call Swift:

   extern int cppAdd(int a, int b) {
       return Test805433::SwiftSide::swiftAdd(a, b);
   }
   

   Note that Test805433 is the C++ namespace associated with my Swift module, and because this is a command-line tool the module name is the name of my tool target.

4. I re-ran the tool and it produced the same result.

Nice!

Please repeat these steps at your end and see if I can make it work. If so, you have a working example that you can crib from for your real project.

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

1. keep swift code in different target(framework type)
2. set swift target build settings:

2.1. SWIFT_INSTALL_OBJC_HEADER to yes. 2.2. C++ and Objective-C Interoperability to C++ / Objective-C++

1. add swift target as Embed in c++ target
2. include <swift target name>-Swift.h where you need to use. and use it.
3. set c++ target :: build settings:: HEADER_SEARCH_PATHS to $(BUILT_PRODUCTS_DIR)/<Swift target name>.framework/Headers

I not see how to update my prevue comment. so I fix it.

1. keep swift code in different target(framework type)
2. set swift target build settings:

2.1. SWIFT_INSTALL_OBJC_HEADER to yes. 2.2. C++ and Objective-C Interoperability to C++ / Objective-C++ 3. add swift target as Embed in c++ target(this automatically add it to be linked) 4. include <swift target name>-Swift.h where you need to use. and use it. 5. set c++ target :: build settings:: HEADER_SEARCH_PATHS to $(BUILT_PRODUCTS_DIR)/<Swift target name>.framework/Headers

abut part 5, I sure someone can give better path or way, but this work.

I not see how to update my prevue comment. so I fix it.

1. keep swift code in different target(framework type)
2. set swift target build settings:
   1. SWIFT_INSTALL_OBJC_HEADER to yes.
   2. C++ and Objective-C Interoperability to C++ / Objective-C++
3. add swift target as Embed in c++ target(this automatically add it to be linked)
4. include <swift target name>-Swift.h where you need to use. and use it.
5. set c++ target :: build settings:: HEADER_SEARCH_PATHS to $(BUILT_PRODUCTS_DIR)/<Swift target name>.framework/Headers

abut part 5, I sure someone can give better path or way, but this work.