Calling Objective C from C++
Calling Objective C from C++
Asset Veranda, the media asset manager I'm working on, uses largely platform-independent code. However, there are some specific functions that need to be called that are platform-specific.
For instance, there is a way to display a file in its native file browser (Finder for macOS or Windows Explorer for Windows). In the case of Windows, this is easy. Include the Windows header file and make a few COM calls. But in the case of macOS, you need to call either their Swift or Objective-C APIs.
Below, I've outlined the simplest way to do this using the CMake build system.
main.cpp
#include <iostream>
#include "ApplePlatformOps.h"
int main() {
// wait for user input
std::cout << "Press Enter to continue..." << std::endl;
std::string filePath;
ASelectFolder(filePath);
std::cout << "Selected: " + filePath << std::endl;
std::cin.get();
return 0;
}
ApplePlatformOps.h
#include
void ASelectFolder(std::string& filePath);
ApplePlatformOps.mm
#include "ApplePlatformOps.h"
#include <Cocoa/Cocoa.h>
void ASelectFolder(std::string& filePath) {
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
NSOpenPanel *openPanel = [NSOpenPanel openPanel];
[openPanel setCanChooseFiles:NO];
[openPanel setCanChooseDirectories:YES];
[openPanel setAllowsMultipleSelection:NO];
NSInteger result = [openPanel runModal];
if (result == NSModalResponseOK) {
NSURL *url = [openPanel URL];
NSString *pathString = [url path];
const char *utf8String = [pathString UTF8String];
filePath = std::string(utf8String);
}
[pool release];
}
CMake file
cmake_minimum_required(VERSION 3.10)
project(MyProject)
set(CMAKE_CXX_STANDARD 17)
# Add the path to the FindCocoa.cmake module
set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_SOURCE_DIR}/cmake/")
# Specify the source files
set(SOURCE_FILES
main.cpp
)
set(HEADER_FILES
)
if(APPLE)
# Add the platform specific files
list(APPEND SOURCE_FILES
ApplePlatformOps.mm
ApplePlatformOps.h
)
# Add the platform specific headers
list(APPEND HEADER_FILES
ApplePlatformOps.h
)
find_library(COCOA_LIBRARY Cocoa)
endif()
add_executable(MyProject ${SOURCE_FILES} ${HEADER_FILES})
if(APPLE)
# Link the necessary libraries
target_link_libraries(MyProject ${COCOA_LIBRARY})
endif()