从Objective C类调用C ++构造函数 [英] Call a C++ constructor from an Objective C class

问题描述

如何从Objective C类中调用C ++构造函数？

  class CppClass {
 public： 
 CppClass（int arg1，const std :: string& arg2）：_arg1（arg1），_arg2（arg2）{} 
 
 // ... 
 private：
 int _arg1; std :: string _arg2; 
}; 
 
 @interface ObjC：NSObject {
 CppClass _cppClass; 
} 
 @end 
 
 @implementation ObjC 
 
  - （id）init 
 {
 self = [super init] ; 
 if（self）
 {
 //在_cppClass上调用CppClass :: CppClass（5，hello）的语法是什么？ 
} 
 return self; 
} 
 @end 
  

解决方案

当我最终在一个情况下，默认构造函数不剪切它，我使实例变量一个指针，然后使用 init中的 new 方法中方法和删除。
$ b $ b

实际上，对于Objective-C实例变量，默认构造函数是相对最近调用的。

没有指定Objective- C语言，更不用说Objective-C ++扩展的规范。苹果公司发布了一份文档，名为 Objective-C编程语言，但它几乎没有提到C ++，所以你经常留在自己的时候，你需要澄清一些不明显的东西。 Clang 邮件列表通常知道更好。

How can I call a C++ constructor from inside an Objective C class?

class CppClass {
public:
    CppClass(int arg1, const std::string& arg2): _arg1(arg1), _arg2(arg2) { }

    // ...
private:
    int _arg1; std::string _arg2;
};

@interface ObjC: NSObject {
    CppClass _cppClass;
}
@end

@implementation ObjC

- (id)init
{
    self = [super init];
    if ( self )
    {
         // what is the syntax to call CppClass::CppClass(5, "hello") on _cppClass?
    }
    return self;
}
@end

解决方案

When I end up in a situation where the default constructor doesn't cut it, I make the instance variable a pointer and then use new in the init method and delete in the dealloc method.

It's a relatively recent thing that default constructors are called at all for Objective-C instance variables, actually.

There is no specification of the Objective-C language, let alone a specification of the Objective-C++ extension. Apple does publish a document called The Objective-C Programming Language, but it barely mentions C++, so you're often left on your own when you need to clarify something unobvious. The guys at the Clang mailing list often know better, though.

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