How to define a constructor in a struct?

[Adam D. Ruppe]

On Sunday, 5 August 2012 at 16:05:54 UTC, Minas Mina wrote:
> I want to make a struct that defines a constructor:

You can't quite do it. A D struct is supposed to always be 
trivial to initialize. You can, however, do a static opCall(), 
constructors that take parameters, and/or disable default 
construction, forcing the user to use one of those other ones.

> I wrote a @disable next to it but same error. I don't 
> understand what the "no body" part means.

You'd write it

@disable this();


What this does is say this struct can't be default defined - the 
user would have to initialize it using one of its other 
constructors.

For example:


struct Test {
    @disable this(); // this makes it so Test t; won't work - you 
have to use a constructor of some sort

    this(int num) {
         // construct it using the number
    }

    // static opCall makes Test() work when you spell it out
    static Test opCall() {
         Test t = Test(1);
         return t;
    }
}

void main() {
	//Test t; // compile error - default construction is diabled

	Test t = Test(); // uses opCall

	Test t2 = Test(5); // uses the constructor with an int param
}