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Override native C++ method with squirrel?
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lapayo
#1 Posted : Wednesday, March 28, 2012 5:04:11 PM(UTC)
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Hello,
I have a short questions:
Is it possible to override native c++ methods within a squirrel script?

I tried the following:
Code:
class TestClass
{
public:
    void doEcho()
    {
        echo();
    }
    virtual void echo()
    {
        std::cout << "parent" << std::endl;
    }
};

in C++ and
Code:
class ExtraClass extends TestClass
{
    function echo()
    {
        ::print("Child")
    }
}

instance <- ExtraClass()
instance.doEcho()

in Squirrel.
But the call in Squirrel still calls the parent echo method.
Is this possible without porting the TestClass to Squirrel?

Thanks in advance,

Simon
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cue
#2 Posted : Wednesday, March 28, 2012 6:06:20 PM(UTC)
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Of course it's not possible. There is no way a Squirrel function can make it into the virtual table of a C++ class. This doesn't make any sense, C++ is compiled, Squirrel is interpreted at run time.
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lapayo on 3/28/2012(UTC)
lapayo
#3 Posted : Wednesday, March 28, 2012 6:23:05 PM(UTC)
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Thanks for your answer.
Do you have an idea how to get a similar result?

What I wanted to do:
Extend the nativ Entity implementation with squirrel and push it to an native EntityManager which updates the entities every frame. For this I wanted to override the update method, so the entity can implement his own update method.


Thanks in advance,

Simon
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flipper
#4 Posted : Wednesday, March 28, 2012 6:30:45 PM(UTC)
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beware, i'm a squirrel noob

maybe you could sq_call a closure and return at the top in virtual void echo, if the closure (echo/update) is in the squirrel class table (or meta table etc)
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cue
#5 Posted : Wednesday, March 28, 2012 7:00:40 PM(UTC)
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lapayo: I don't think this sort of coupling (as you describe it) is possible, at least I can't think of a way to implement it. If you want a C++ manager class to be able to handle both, C++ entity classes and Squirrel entity classes, you need to make an entity interface and two implementations. The first implementation is the C++ entity and the second is a wrapper around a Squirrel class instance which simply calls the respective squirrel functions of the wrapped squirrel instance.
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lapayo on 3/28/2012(UTC)
lapayo
#6 Posted : Wednesday, March 28, 2012 7:58:37 PM(UTC)
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Thanks for your idea.
I am currently trying to implement it but have some problems.

How can I check if there is an class with the name an the create an instance from within c++ from the class?
And how can I then check if method xyz exists in the squirrel class?

I am using Sqrat for this.

Thanks in advance,

Simon
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cue
#7 Posted : Thursday, March 29, 2012 11:12:31 PM(UTC)
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Sorry, I don't use Sqrat, so I can't help you on that.

If you were to use Squirrel's C API: sq_get() retrieves a slot from a table/class/array and sq_createinstance() creates a new instance of a class, look them up in the documentation.
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lapayo
#8 Posted : Saturday, March 31, 2012 12:53:54 PM(UTC)
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Thanks for your help.
With trail-and-error I found a way to do it with Sqrat
The following works:
Code:
Function func(RootTable(vm), L"ExtraClass");

        if(!func.IsNull())
        {

            Object obj = func.Evaluate<Object>();
            Function func2(obj, L"echo");
            if(!func2.IsNull())
            {
                func2.Execute();
            }

        }

ExtraClass is my class I am creating.
echo() is the method I want to call.
Everything works as expected. :)
(I don´t know how "dirty" this solution is :D
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