• =?iso-8859-1?Q?Robert_M._M=FCnch?= (21/21) Jan 04 2020 This following code gives an error: "constructor a.this missing
• H. S. Teoh (16/26) Jan 04 2020 [...]
• Paul Backus (9/26) Jan 05 2020 You could try something like this:

=?iso-8859-1?Q?Robert_M._M=FCnch?= <robert.muench saphirion.com> writes:

This following code gives an error: "constructor a.this missing 
initializer for const field myThing"

class a {
	const myThing*;

	init(){
		myThing = initMyThing();
	}
	
	this(){
		init();
	}
}

I have to explicitly set the const field inside this(). As long as I 
only have one constructor that's OK. I prefer to have an init() 
function to collect all things to setup an object.

Shouldn't the compiler find out that myThing is set during construction 
in this case?

-- 
Robert M. Münch
http://www.saphirion.com
smarter | better | faster

"H. S. Teoh" <hsteoh quickfur.ath.cx> writes:

On Sat, Jan 04, 2020 at 03:50:54PM +0100, Robert M. Münch via Digitalmars-d
wrote:
[...]
 class a {
 	const myThing*;
 
 	init(){
 		myThing = initMyThing();
 	}
 	
 	this(){
 		init();
 	}

[...]

In general, it's a very bad idea to name a member function or variable
.init, because .init is supposed to be a bitwise copy of the initial
state of a type. While the language currently doesn't regard it as an
error to redefine .init to be something else, IMO it should, because it
breaks a lot of assumptions in generic code, and in general just causes
too much trouble to be worth it. I wouldn't be surprised if you came
across compiler bugs if you redefine .init this way.

If you didn't intentionally override .init, the best solution is to
rename it to something that doesn't clash with the built-in expectations
of .init, like initialize() or some such. That should fix your problem.


T

-- 
It is not the employer who pays the wages. Employers only handle the money. It
is the customer who pays the wages. -- Henry Ford

Paul Backus <snarwin gmail.com> writes:

On Saturday, 4 January 2020 at 14:50:54 UTC, Robert M. Münch 
wrote:
 This following code gives an error: "constructor a.this missing 
 initializer for const field myThing"

 class a {
 	const myThing*;

 	init(){
 		myThing = initMyThing();
 	}
 	
 	this(){
 		init();
 	}
 }

 I have to explicitly set the const field inside this(). As long 
 as I only have one constructor that's OK. I prefer to have an 
 init() function to collect all things to setup an object.

 Shouldn't the compiler find out that myThing is set during 
 construction in this case?

You could try something like this:

enum string initThing = q{
     myThing = initMyThing();
};

this() {
     mixin(initThing);
}