How to use D classes from C++
Mohe Ud Din SheikhOverview
The D programming language is compatible with C++, which allows us to connect the two by simply using external(C++) interface C. We can use classes defined in D program files in our C++ programs.
To use the class in our C++ program, we need to compile the D program file separately, and by using this compiled file, we can use the class in D in our C++ program.
Let's look at the syntax.
Syntax
extern (C++) void call(C);
To use the D class, we have to use extern(C++). Then we add the call() function, the function we used in the C++ program file.
Example
import std.stdio ;
extern (C++) void call(C);
extern (C++) interface C
{
void show();
}
//inheriting D class from c++ class
class D : C
{
extern (C++) void show()
{
writeln("I came from D class");
}
}
void main()
{ //Declaring d obeject of d class
D d = new D();
call(d);
}Explanation
In the call.cpp file, we do the following actions:
- Line 4: We declare a
virtualfunction that overrides theclassfunction. - Line 8: We declare a
callfunction in which we passclass cand a pointer-type variable,p, as parameters. - Line 9: We use the
ppointer to point to theshowfunction overridden by the Dshow()function.
In the main.d file, we write the following:
- Line 2: We use
extern(C++)and then add thecall ()function which we used in the C++ program file. - Line 3: We used
extern(C++)interface Cto use the class defined within a D program file in our C++ program. - Line 8: We inherit the D program class from the C class defined in our C++ program.
- Line 10: We use
extern(C++)void show(), in which we useextern(C++)to show that it's from an external C++ program file. We usevoid show()to inherit the show member function of that program,g++ -c sum.cppdmd main.d sum.o -L-lstdc++ && ./main.
Note: To run this program locally, we have to compile the D file separately by using the
dmd -c main.dcommand in the terminal, and after the compilation, we need to use the commandg++ call.cpp main.o -lphobos2 -pthread -o call && ./callto run the program.
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