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Dynamically compile classes


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#1 mk1x86   Members   -  Reputation: 442

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Posted 09 July 2013 - 07:52 AM

Hello there. Once again, thank you for this great scripting language.

As I understand adding script sections to a module is more or less the same as concatenating several code snippets (except for error messages). When building my code everything inside the module is discarded and replaced by the script sections I added. Is this correct?

 

Functions as well as global variables can be dynamically compiled into a module. What I need is adding class declarations on the fly, so I can add new classes while the game progresses and create instances of them. Is this is possible and if not, how difficult would it be to add such a feature?



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#2 Andreas Jonsson   Moderators   -  Reputation: 3450

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Posted 10 July 2013 - 07:49 AM

Hi,

 

yes, you're correct. When calling Build() on a module it will discard everything previously built in that module and compile the script sections that have been added since the last call to Build().

 

Support for adding class declarations to an already compiled module may not be too difficult to implement, since no other code is currently referring to the new class. The most difficult part, would be to make sure not changes to the module is made in case of any compilation errors in the new class declaration. Adding support for removing class declarations is much harder, because then it is necessary to guarantee consistency with any other code that may be referring to the class.

 

However, are you sure this is really what you need? Probably you can accomplish what you need by using multiple modules instead. Each module is independent, so you can add and remove modules on the fly as needed. Of course, depending on your needs you may need to implement some way to allow the code in the different modules to communicate with each other, possibly through some message queue or some similar manner.


AngelCode.com - game development and more - Reference DB - game developer references
AngelScript - free scripting library - BMFont - free bitmap font generator - Tower - free puzzle game

#3 mk1x86   Members   -  Reputation: 442

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Posted 10 July 2013 - 09:26 AM

I have a few different C++ classes in my game, that can interact. "Props" like exploding barrels, vending machines, "Doors", "Lights" and "SoundSources". Each object shall react on certain events (being clicked, being "used" by a player, ...). To describe the object's internal states and reactions I'd like to use an angelscript class. For a vending machine it can hold data for the cans left, and the amount of money it has received. It should also be able to add a coke can to the player's inventory, via a line like this: player.add(createItem("coke can"));

An instance of the angelscript class is assigned to the actual C++ instance. Events are processed by calling a method of the as instance, which can only access other as instances (the c++ classes are not exposed). AS classes are derived from a base class. For example class VendingMachine : Prop { ... }

Subclasses only need to interact with the base classes. During the course of the game new objects may be created. A flare "Item" class could for example spawn a new "Light" class. This light is loaded on the fly and it may use a sub class of "Light" that is not yet built into the module.

 

Currently adding new objects is only possible if ALL classes, that MAY be used, are built in a single build call. I'd like to add new classes only when an object is loaded that uses a class not yet built into the module.

 

I hope I could clarify my problem. If there is an easier way to achieve this, please enlighten me. :)



#4 Andreas Jonsson   Moderators   -  Reputation: 3450

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Posted 10 July 2013 - 10:59 AM

You should take a look at the 'game' sample in the AngelScript SDK. Even though it is a very simplified example, it should be able to show you how to separate your scripts in multiple modules. Alternatively you may take a look at my prototype game engine. A word of warning though, as it is a prototype, don't expect polished code. I only use it to experiment with ideas I have.

 

Basically, what you want is to have one script module for each type of entity in your game. This will allow you to load the scripts that contain the logic for that type of entity only when it will actually be used for the first time. 


AngelCode.com - game development and more - Reference DB - game developer references
AngelScript - free scripting library - BMFont - free bitmap font generator - Tower - free puzzle game




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