SwiftBoostExample

I’m new to Swift and it wasn’t immediately clear how to easily import and use Boost Framework functions, so here’s a very basic example for anyone else wanting to do this.

Requirements

• Xcode
• Swift 5.7+

Additional Notes

• This method uses the -enable-experimental-cxx-interop flag which will likely be superseded by -cxx-interoperability-mode=swift-5.9 when Swift 5.9 is officially released

• For more information regarding experimental Swift C++ interoperability see archived README here: https://github.com/apple/swift/blob/05d44b128f1f45cdcf58ebb8df32d223390f6798/docs/CppInteroperability/GettingStartedWithC++Interop.md

• For more information regarding production-ready Swift C++ interopablility see current README here: https://github.com/apple/swift/blob/main/docs/CppInteroperability/GettingStartedWithC++Interop.md

• For details about Swift 5.9 see release announcement here: https://forums.swift.org/t/swift-5-9-release-process/63557

Quick Start

• Clone the repository
• Load the included Workspace in Xcode: ./SwiftBoostExample.xcworkspace
• Update signing & capabilities if needed
• Select destination
• And run!

Reference

Installing Boost via CocoaPods (optional)

I found it easiest to install Boost using CocoaPods since it automatically creates a Workspace and .xconfig file with the appropriate header search paths. Here’s how to do that:

• Install CocoaPods. See instructions here: https://cocoapods.org/
• Create a Podfile with the following contents:

target 'SwiftBoostExample' do
  use_frameworks!
  pod 'boost', '~> 1.51.0'
end

• Open terminal and run pod install in the repository root. It may take a very long time to complete the first time.

(Note: Boost 1.51 is rather old but other pod versions were throwing errors during compilation due to missing includes in the podspec. See https://github.com/CocoaPods/Specs/tree/master/Specs/9/9/d/boost for available podspec versions)

Updating compiler flags

• Add the following flags to Build Settings -> Other Swift Flags:

-enable-experimental-cxx-interop
-I./BoostFramework

• If you didn’t install with CocoaPods then you also need to add the Boost path to Build Settings -> Swift Compiler - Search Paths -> Import Paths

Create BoostFramework group, header and modulemap

BoostFramework.hpp example

#ifndef BoostFramework_hpp
#define BoostFramework_hpp

#define BOOST_NO_EXCEPTIONS

#include <stdio.h>
#include <boost/math/special_functions/prime.hpp>
#include <boost/math/special_functions/zeta.hpp>
#include <boost/throw_exception.hpp>

uint32_t prime(uint32_t n) {
    return boost::math::prime(n - 1);
}

double zeta(double z) {
    return boost::math::zeta(z);
}

void boost::throw_exception(std::exception const & e){
  //TODO: handle exception
}

#endif /* BoostFramework_hpp */

module.modulemap

module BoostFramework {
    header "BoostFramework.hpp"
    requires cplusplus
}

GitHub

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