On 18/10/2014 1:40 am, Michael Heuer wrote:
Gonzalo wrote:
I have this (unexpected?) behaviour when casting. I can cast a object to its
parent class, but the methods that get executed are still their own (and
viceversa). I.e.:
----------------------------------
public class Parent {
fun void test() {
<<< "Parent" >>>;
}
}
class Child extends Parent {
fun void test() {
<<< "Child" >>>;
}
}
Parent p;
Child @ ch;
p $ Child @=> ch;
ch.test(); // prints Parent
This shouldn't work, because p !instanceof Child, the cast should be a
compiler error.
Thanks Michael. You're right, and in fact it doesn't work at all. Now
that I've tried, ch can not call methods exclusive to Child either
(Assertion failed: (m_offset < obj->vtable->funcs.size()), function
execute, file chuck_instr.cpp, line 4765).
Is this intended behavior? What's the point of casting then?
I typically only use casting when pulling object references out of
data structures that hold arrays of Object references, e.g. an
ArrayList
https://github.com/heuermh/lick/blob/master/Freeze.ck#L73
Of course, I see. I was trying to use casting to bypass the lack of
constructors, bad misuse.
I might describe too what I'm trying to do, maybe there's a better approach.
I have a .create method in Parent that returns a Parent object, and I wanted
to create that same method in Child, but I can't do it because the arguments
are the same, and it won't let me overwrite the method when only the return
type changes. So to create a child with the .create method, I do this:
Parent.create(...) $ Child @=> Child ch;
Which works, but then it still behaves as a parent, so it defeats the whole
purpose.
Having proper constructors in ChucK would help here
https://github.com/spencersalazar/chuck/issues/32
A workaround might be to include the classname in your create methods
class Parent {
fun static Parent createParent(...) { }
}
class Child extends Parent {
fun static Child createChild(...) { }
}
Yes, that might be the way to go. I use init() methods as a workaround
for constructors, so my normal instantiations look like:
MyClass c;
c.init(...);
Not very nice, which is why I was trying to have the static 'create'
methods. I'm thinking of having a global Make class, and put all my
static initializers there. Which would look something like:
class Make {
fun static Parent Parent(args) {
Parent p;
p.init(args);
return p;
}
....
}
Make.Parent(...) @=> Parent p;
Ugly class, but nicer to call than Parent.createParent(args) ?
michael
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