qestion about passing the array of string into DLL

[FuliangQ]

hi,

  i encounter a question about passing string's array into a DLL ,

  first i declare the funtion in .mqh as follows : void f(string& array[]) ;  , but this failed .

  and then i  try to do this by declare the function : void f(string& str) ;

  with a for loop , i push string array into dll as follows :

                .......

               string str[5]= {"sddsa" , "ddass" , "dsdfasdwe" , "wwer2" , "e23"} ;

               for(int i = 0 ; i < 5 ; i ++)

                    f(str[i]) ;

  but   in the function f , i didn't get the right value of the str[i] , and  i print the address of str :   

                addr0  = 038C8D48

                addr1  = 038C8D54

                addr2  = 038C8D60

                addr3  = 038C8D6C

                addr4  = 038C8D78 

so , my question is how to access the element in a string's array .

 

thanks in advance . 

[Rashid Umarov]

Have you read article How to Exchange Data: A DLL for MQL5 in 10 Minutes?

[FuliangQ]

Rosh:
Have you read article How to Exchange Data: A DLL for MQL5 in 10 Minutes?

 

yes , i have read , and i know i can pass a string with the form f(string& str) ;

but i found i can not pass the array of strings , eff f(string& sting[]) ;

so if i can not  access the string's array of MT5 in DLL  .

thanks . 

[Andriy Voitenko]

In this section MQL5 Help is written:

Classes, string arrays or complex objects that contain strings and/or dynamic arrays of any types cannot be passed as a parameter to functions imported from DLL.

But you can use array of char for ANSI string declaration.

MQL5 script:

//+------------------------------------------------------------------+
//|                                                Array_strings.mq5 |
//|                        Copyright 2010, MetaQuotes Software Corp. |
//|                                              http://www.mql5.com |
//+------------------------------------------------------------------+
#property copyright "Copyright 2010, MetaQuotes Software Corp."
#property link      "http://www.mql5.com"
#property version   "1.00"

struct char_array
{
   char a[256];
   char b[256];
   char c[256];
};

char_array my_ar;


#import "mylib.dll"
   void f(char_array &my_ar); //pass structure which contains the ANSI strings
#import

//+------------------------------------------------------------------+
void OnStart()
//+------------------------------------------------------------------+
  {
   // initialize strings
   string str1="first string";
      StringToCharArray(str1, my_ar.a);
   str1="second string";     
      StringToCharArray(str1, my_ar.b);
   str1="third string";    
      StringToCharArray(str1, my_ar.c);
   
   
   func(my_ar);// print and change first string (my_ar.a) in MQL code 
   f(my_ar);   // change first string (my_ar.a) in DLL code 
   
   Print(CharArrayToString(my_ar.a));
     
  }

//+------------------------------------------------------------------+
void func(char_array &my_ar)
//+------------------------------------------------------------------+
{
   string str;
   str = CharArrayToString(my_ar.a);
   Print(str);                    // print string  
   str = str + " + add string";    // change string 
   StringToCharArray(str,my_ar.a); // save changes
}

DLL code

#include <windows.h>

struct char_array
{
   char a[256];
   char b[256];
   char c[256];
};

void __stdcall f(char_array &my_ar)
 {
         strcpy(&my_ar.a[0], "my new string");// change string
 }

 

 

 

[FuliangQ]

avoitenko:

In this section MQL5 Help is written:

But you can use array of char for ANSI string declaration.

MQL5 script:

DLL code

thank you very much , good !