Can I have Swift, Objective-C, C and C++ files in the same Xcode project?
YES.
You can mix Swift
, C
, C++
, Objective-C
& Objective-C++
files in the same Xcode project.
C
// Declaration: C.h#ifndef C_h#define C_h#ifdef __cplusplusextern "C" {#endif void hello_c(const char * name);#ifdef __cplusplus}#endif#endif /* C_h */// Definition: C.c#include "C.h"#include <stdio.h>void hello_c(const char * name) { printf("Hello %s in C\n", name);}
C++
// Declaration: CPP.hpp#pragma once#include <string>class CPP {public: void hello_cpp(const std::string& name);};// Definition: CPP.cpp#include "CPP.hpp"#include <iostream>using namespace std;void CPP::hello_cpp(const std::string& name) { cout << "Hello " << name << " in C++" << endl;}
Objective-C wrapper for C++
// Declaration: CPP-Wrapper.h#import <Foundation/Foundation.h>@interface CPP_Wrapper : NSObject- (void)hello_cpp_wrapped:(NSString *)name;@end// Definition: CPP-Wrapper.mm#import "CPP-Wrapper.h"#include "CPP.hpp"@implementation CPP_Wrapper- (void)hello_cpp_wrapped:(NSString *)name { CPP cpp; cpp.hello_cpp([name cStringUsingEncoding:NSUTF8StringEncoding]);}@end
Objective-C
// Declaration: Objective-C.h#import <Foundation/Foundation.h>@interface Objective_C : NSObject- (void)hello_objectiveC:(NSString *)name;@end// Definition: Objective-C.m#import "Objective-C.h"@implementation Objective_C- (void)hello_objectiveC:(NSString*)name { printf("Hello %s in Objective-C\n", [name cStringUsingEncoding:NSUTF8StringEncoding]);}@end
Objective-C++
// Declaration: Objective-CPP.h#import <Foundation/Foundation.h>@interface Objective_CPP : NSObject- (void)hello_objectiveCpp:(NSString *)name;@end// Definition: Objective-CPP.mm#include <iostream>#import "Objective-CPP.h"using namespace std;@implementation Objective_CPP- (void)hello_objectiveCpp:(NSString *)name { cout << "Hello " << [name cStringUsingEncoding:NSUTF8StringEncoding] << " in Objective-C++\n";}@end
Swift
// Declaration & definition: Swift.swiftfunc hello_swift(_ name: String) { print("Hello \(name) in Swift")}
Bridging-Header.h
Cannot import CPP.hpp
header file, not because of it's naming convention, but because it contains the class
keyword.
#import "C.h"#import "CPP-Wrapper.h"#import "Objective-C.h"#import "Objective-CPP.h"
Invocation from Swift
// Invoke Chello_c("World".cStringUsingEncoding(NSUTF8StringEncoding))// Can't Invoke C++ without a wrapper// CPP().hello_cpp("World".cStringUsingEncoding(NSUTF8StringEncoding))// Invoke C++ through Objective-CCPP_Wrapper().hello_cpp_wrapped("World")// Invoke Objective-CObjective_C().hello_objectiveC("World")// Invoke Objective-C++Objective_CPP().hello_objectiveCpp("World")// Invoke SwiftSwift().hello_swift("World")
.h (Headers)
(See item 3 in this Stack Overflow answer)
.h: this is the tricky part, since they are ambiguously used for all flavors of C, ++ or not, Objective or not. When a .h does not contain a single C++ keyword, like class, it can be added to the ...Bridging-Header.h, and will expose whatever function the corresponding .c or .cpp functionalities it declares. Otherwise, that header must be wrapped in either a pure C or Objective-C API.
Output
Hello World in CHello World in C++Hello World in Objective-CHello World in Objective-C++Hello World in Swift
Comments
Yes. You only need wrap C++
into C
or Objective-C
to use in Swift
.
Indeed, I have a project that does exactly that. C++
for the thrust of the abstract cross-platform model stuff with some C
parts underneath; Objective-C
to wrap the C++
classes for Swift
purposes, Swift
to bind all that to a subclass of NSDocument
, with some custom views that interrogate the C
stuff.
Added the extern "C"
wrapper as per your excellent suggestion. To invoke the C method void hello_c(const char * name)
from C++ method hello_cpp(const std::string& name)
, add #include "C.h"
and call hello_c(name.c_str());
.
The new SO-32541268: Now with parameters!
► Find this solution on GitHub and additional details on Swift Recipes.