ios - Calling C++ from Objective-C -

for of have been able call c++ code objective-c, please enlighten me?

this link says need wrap c++ code using technique describes in article. looks still have problems.

this link says long objective-c class calling c++ class has been converted .mm (objective-c++) class 2 should work nicely together.

each of these approaches causing me grief minute try add method call. can please give me code simple hello world ios app uses objective-c "hello" part , c++ class "world" part objective-c++ class in middle? or still have entire concept wrong?

essentially need objc class .mm extension calls objc class .mm extension. second 1 used c++ wrapper class. wrapper class call actual .cpp class. it's little tricky, i'm going give verbose code. here overview of project:

in objc code (viewcontroller) call cplusplusmmclass

- (ibaction)buttonpushed:(uibutton *)sender {     self.mmclass = [[cplusplusmmclass alloc]init];  // bad practice; showing code     nsstring *str = [self.mmclass fetchstringfromcplusplus];     [self populatelabel:str]; } 

here cplusplusmmclass .h , .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 

here wrapperclass .h , .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 

here purecplusplusclass .h , .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; } 

this code not perfect! i'm having trouble namespace test being recognized. i'll update when can.

but should there!!!!