从Objective-C调用C ++ [英] Calling C++ from Objective-C

问题描述

对于那些已经能够成功从Objective-C调用C ++代码的人，请给我启发?

For those of you who have successfully been able to call C++ code from Objective-C, will you please enlighten me?

此链接表示您需要使用他在文章中描述的技术来包装C ++代码.看起来不错，但我仍然有问题.

This link says you need to wrap your C++ code using a technique he describes in his article. It looks good but I still have problems.

此链接说只要将调用C ++类的Objective-C类转换为.mm(Objective-C ++)类，那么这两个类就可以很好地协同工作.

This link says that as long as the Objective-C class calling the C++ class has been converted to a .mm (Objective-C++) class then the two should work nicely together.

这些方法中的每一种都使我在尝试添加方法调用的那一刻感到悲痛.有人可以给我提供一个简单的Hello World iOS应用程序的代码，该应用程序将Objective-C用于"Hello"部分，将C ++类用于"World"部分，中间使用Objective-C ++类吗?还是我仍然对整个概念有误?

Each of these approaches are causing me grief the minute I try to add a method call. Can somebody please give me code for a simple Hello World iOS app that uses Objective-C for the "Hello" part and a C++ class for the "World" part with an Objective-C++ class in the middle? Or do I still have the entire concept wrong?

推荐答案

基本上，您需要一个扩展名为.mm的ObjC类，并调用一个扩展名为.mm的ObjC类.第二个将用作C ++包装器类.包装器类将调用您的实际.cpp类.这有点棘手，所以我将给您一些冗长的代码.这是该项目的概述:

Essentially you need an ObjC class with .mm extension that calls an ObjC class with .mm extension. The second one will be used as a C++ wrapper class. The wrapper class will call your actual .cpp class. It's a little tricky, so I'm going to give you some verbose code. Here is an overview of the project:

在您的ObjC代码(ViewController)中，您将调用CplusplusMMClass

In your ObjC code (ViewController) you would call the CplusplusMMClass

- (IBAction)buttonPushed:(UIButton *)sender {
    self.mmclass = [[CplusplusMMClass alloc]init];  // bad practice; but showing code
    NSString *str = [self.mmclass fetchStringFromCplusplus];
    [self populateLabel:str];
}

这是CplusplusMMClass .h和.mm

Here is the CplusplusMMClass .h and .mm

#import <Foundation/Foundation.h>
#import "WrapperClass.h"

@interface CplusplusMMClass : NSObject
@end

@interface CplusplusMMClass()
@property (nonatomic, strong) WrapperClass *wrapper;
- (NSString*)fetchStringFromCplusplus;
@end

---

#import "CplusplusMMClass.h"
#import "WrapperClass.h"

@implementation CplusplusMMClass

- (NSString*)fetchStringFromCplusplus {
    self.wrapper = [[WrapperClass alloc] init];
    NSString * result = [self.wrapper getHelloString];
    return result;
}

@end

这里是WrapperClass .h和.mm

Here is WrapperClass .h and .mm

#ifndef HEADERFILE_H
#define HEADERFILE_H

#import <Foundation/Foundation.h>

#if __cplusplus

#include "PureCplusplusClass.h"

@interface WrapperClass : NSObject
@end

@interface WrapperClass ()
- (NSString *)getHelloString;
@end


#endif
#endif

---

#import "WrapperClass.h"

#include "WrapperClass.h"
#include "PureCplusplusClass.h"

using namespace test;

@interface WrapperClass ()
@property (nonatomic) HelloTest helloTest;
@end

@implementation WrapperClass

- (NSString *)getHelloString {
    self.helloTest = *(new HelloTest);
    std::string str = self.helloTest.getHelloString();
    NSString* result = [[NSString alloc] initWithUTF8String:str.c_str()];
    return result;
}

@end

这是PureCplusplusClass .h和.cpp

Here is the PureCplusplusClass .h and .cpp

#ifndef __HelloWorld__PureCplusplusClass__
#define __HelloWorld__PureCplusplusClass__

#include <stdio.h>
#include <string>

using namespace std;

namespace test {
    class HelloTest
    {
    public:
        std::string getHelloString();
    };
}

#endif /* defined(__HelloWorld__PureCplusplusClass__) */

---

#include <stdio.h>
#include <string>

std::string test::HelloTest::getHelloString() {
    std::string outString = "Hello World";
    return outString;
}

此代码并不完美！我无法识别名称空间测试.我会在可能的时候更新.

This code is not perfect! I'm having trouble with the namespace test being recognized. I'll update when I can.

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