Cannot pass by reference in D language

Question

I have a constructor inside the class testclass

@safe public nothrow this(ref Socket socket) {
    // Inside class modulename.classname
    this.socket = socket;
}

When I initialize an object of this type in my main method however, I got a few compile errors.

void main() {
    auto variablename = new modulename.classname(
        cast(Socket) new TcpSocket() // main.d line 5
    );
}

Errors:

main.d(5): Error: constructor testmodule.testclass.this (ref 
Socket socket) is not callable using argument types (Socket)
main.d(5): Error: no constructor for testclass

Why cannot I pass the socket by reference?

Answer 1

you shouldn't need to pass classes by ref

classes are kept by reference by default (to avoid the slicing problem when inheriting) so you are only passing a pointer in both cases anyway

the problem in your code is that cast(Socket) new TcpSocket() is a rvalue which can't be assigned to and thus cannot be passed by ref