How to guide:

Install Cmake

First install Homebrew using the following command:

/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"

Now install cmake:

brew install cmake
cmake --version

You should see an output like this:

cmake version 3.31.6

Build C++ Library with ios-cmake toolchain

Now create a folder to build your C++ library, in our case NLOPT, using ios-cmake toolchain.

mkdir nlopt_ios && cd nlopt_ios

# Clone the NLOPT repository
git clone https://github.com/stevengj/nlopt.git

# Clone the ios-cmake toolchain
git clone https://github.com/leetal/ios-cmake.git

Now build and install the NLOPT library for device (arm64)

mkdir build_device && cd build_device

cmake -G Xcode \
    -DCMAKE_TOOLCHAIN_FILE=../ios-cmake/ios.toolchain.cmake \
    -DPLATFORM=OS64 \
    -DCMAKE_INSTALL_PREFIX=../install_device \
    -DCMAKE_CONFIGURATION_TYPES="Release" \
    ../nlopt

cmake --build . --config Release --target install

Do the same for building and installing for the simulator (x86_64)

cd ..
mkdir build_simulator && cd build_simulator

cmake -G Xcode \
    -DCMAKE_TOOLCHAIN_FILE=../ios-cmake/ios.toolchain.cmake \
    -DPLATFORM=SIMULATOR64 \
    -DCMAKE_INSTALL_PREFIX=../install_simulator \
    -DCMAKE_CONFIGURATION_TYPES="Release" \
    ../nlopt

cmake --build . --config Release --target install

The install_device folder should have the following folder structure:

include/
├── nlopt.h
└── nlopt.hpp
lib/
├── cmake/
│   └── [CMake configuration files]
├── libnlopt.1.0.0.dylib
├── libnlopt.1.dylib
├── libnlopt.dylib
└── pkgconfig/
    └── [Package configuration files]
share/
└── man/
    └── [Man page files]

And similar for the install_simulator folder.

Creating the Framework file

We will use a script shared in the file create_nlopt_framework.sh to convert the compiled library files into a framework for Xcode.

In this script, change the following variables:

OUT_DIR="path/to/folder/nlopt_ios/framework"
DYLIB_DEVICE="path/to/file/nlopt_ios/install_device/lib/libnlopt.dylib"
DYLIB_SIMULATOR="path/to/file/nlopt_ios/install_simulator/lib/libnlopt.dylib"
HEADERS_DIR="path/to/folder/nlopt_ios/install/include"

We also need to get the codesigning identity to sign the framework. This you can get with the following command:

security find-identity -v -p codesigning

You should get a code of around 40 characters. Paste it to the variable CODESIGN_IDENTITY in the create_nlopt_framework.sh file as follows:

CODESIGN_IDENTITY="YOUR Codesign ID"

Also make sure to change the CFBundleIdentifier key in the Info.plist file code inside the create_nlopt_framework.sh file.

Set the correct permissions after editing the file and run the file:

chmod +x /path/to/nlopt_ios/create_nlopt_framework.sh
/path/to/nlopt_ios/create_nlopt_framework.sh

You should now see the framework file in the nlopt_ios/framework/nlopt.framework path. Lets verify if we have the succeeded in creating the framework file:

cd /path/to/nlopt_ios/framework/nlopt.framework
ls -l
lipo -info nlopt

You should see the following in your terminal output:

Architectures in the fat file: nlopt are: arm64 x86_64