在同一个项目的C函数中调用C ++类方法

Question

i have a Qt Gui project that formed mixed-language with C and C++. I must use a C++ class function in my C source. How to call it? Can u help me?

C++ function to call

 void MainWindow::putsDisplay(int Line, char *string)
{
    if(Line == 0)
    {
        ui->customerLine_1->setPlainText(string);
    }

    if(Line == 1)
    {
        ui->customerLine_2->setPlainText(string);
    }

    if(Line == 2)
    {
        ui->cashierLine_1->setPlainText(string);
    }

    if(Line == 3)
    {
        ui->cashierLine_2->setPlainText(string);
    }

    if(Line == 4)
    {
        ui->printerArea->setPlainText(string);
    }
}

Answer 1

You can not use a C++ method directly, you have to create a function in order to call your object's method. Here is an example (part of a C++ file):

extern C 
{

    void   example(int Line, char *string)
    {
       static MainWindow win;

       win.putsDisplay(Line, string); 
    }

}

C code:

int main()
{
    example(42, "it is an example");
    return 0;
}

extern C will disabled name mangling, so example() can be called from C code. You can keep static MainWindow win; , or made it global or whatever, but you will need an MainWindow object.

Answer 2

Remember, C is a subset of C++.

You can name the file that has the C code as xC or x.cpp and compile it with the rest of the files with c++ compiler. Then you will be able to call the C++ method from the C code.