Constructor and Destructor for Types

BlitzMax Forums/BlitzMax Programming/Constructor and Destructor for Types

Mirko

(Posted 2005) [#1]

After looking through the documentation and searching the forum i am still not sure.

Is it true that BM does not have some kind of destructor and constructor which is automatically called when creating a type.

I mean something like classes in C++ have.

If so it would be nice to have them like a
OnCreate and OnDestroy function for every type. So that this functions are automatically called when a type is created with new or when a type is destroyed by the garbagecollector.

Mirko

PS: OK, the OnCreate can be called by my programm after it creates a type using new, but the OnDestroy should occure when the type is killed by the gb, as i might not know how long the type is used. Still, having both would be nice.

PowerPC603

(Posted 2005) [#2]

Those do exist, but you have to declare them and you'll have to specify what they should do when they are created/destroyed:

Type test
	Method New() ' Constructor method
		Print "Hey, you've just created a new test-instance"
	End Method

	Method Delete() ' Destructor method
		Print "You've just destroyed a test-instance"
	End Method
End Type

a:test = New test ' Create a new instance of "test"

a = Null ' Set "a" to point to nothing (so it can be destroyed at the next FlushMem)
FlushMem ' Destroy all unreferenced objects

Bot Builder

(Posted 2005) [#3]

On destroy can be don with a Delete method automatically caled by the gc.

N	(Posted 2005) [#4]

A few things to note: you can't have arguments in the 'constructor' (it's not really a constructor, in my opinion), and you can't call the destructor. Or you shouldn't be able to, anyways.

If you want to have a pseudo-constructor, create a static function in the class and call it Create, that way it's pretty obvious what it does. For example, my entity classes have a static function Spawn that, well, spawns one of them at a given point.

Probably already knew that, but I figured I'd mention it.

Mirko

(Posted 2005) [#5]

Hey, thanx to all of you. I did not know that.
Is it documentet somewhere or how do you know about New and Delete Methods?

N	(Posted 2005) [#6]

It's under the language reference for user defined types.