How to use the C++ classes in D
Overview
C++ classes are commonly used in D programs. D classes are incompatible with C++ classes, hence interfaces in D can be used to import C++ classes using extern(C++). The C++ program must have a function that creates an object of that class. To use C++ classes, we compile the .cpp file separately before the D program can use them.
Syntax
extern (C++) {interface Math {int multiply(int i, int j);}Math getMath();}
As mentioned earlier, extern (C++) is used and a D interface is created which contains the methods from the C++ class to be used in its program.
Note: The C++ class that is to be used by D must have virtual methods in order to be used by D.
Example
main.d
base.cpp
extern (C++) {interface Math {int multiply(int i, int j);}Math getMath();}void main() {Math a = getMath();a.multiply(2,3);}
Explanation
In the base.cpp file,
- Line 5: We create a class that contains one public method of multiplication.
- Line 14: We create function that creates the
Mathclass object so that the D program can initialize an instance of this class.
In the main.d file,
- Line 1: We use
extern(C++)to indicate that code from C++ will be used in this program. - Line 2: We create an interface that contains the same member function as the C++ class.
- Line 5: We add the
getMath()function from C++ because it will be used to create an object of the C++ class. - Line 9: We create the C++ class object.
- Line 10: We call the
multiplyfunction from the class.
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