Type-problem aargh!
Blitz3D Forums/Blitz3D Programming/Type-problem aargh!
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| Hi there, I have two different types: .player, and .enemy, and I want to be able to use the same function for controlling either .player or .enemy. example: (theoretical) type player field gfx end type type enemy field gfx end type e.enemy = new enemy p.player = new player function movePerson(person) positionEntity person\gfx,10,10,10 end function ...And then I want to say something like: movePerson(e.enemy) or movePerson(p.player) But this is not possible!!! Isn't there a way to solve this so that I can use the same function for more than one type of type (hehe..)?? Best regards, Jesper Colding - Jørgensen |
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| Not really. You're asking for overloaded functions and after the last bruhaha over that I don't think you want to go there. Object Orientation is a four letter word around here. |
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There is a way to solve it, and I used the method in my GUI system.Type GUI_Object Field ObjectType Field ObjectHandle EndType ObjectType is a number which defines which type the object is. ObjectHandle is a pointer to that type. This is how I create a new object: ThisGUIObject.GUI_Object = New GUI_Object ThisText.GUI_Text = New GUI_Text ThisGUIObject\ObjectType = GUI_OBJECTTYPE_TEXT ThisGUIObject\ObjectHandle = Handle(ThisText) Note how ObjectType is set to a constant that tells it that the pointer converted to an int and stored in ObjectHandle is of type TEXT. And this is a function which returns the entity stored in any one of my types: Function GUI_GetObjectEntity(ThisGUIObject.GUI_Object) ObjectType = ThisGUIObject\ObjectType ObjectHandle = ThisGUIObject\ObjectHandle Select ObjectType Case GUI_OBJECTTYPE_DATABAR ThisDataBar.GUI_DataBar = Object.GUI_DataBar(ObjectHandle) Avatar = ThisDataBar\Avatar Case GUI_OBJECTTYPE_DATAARC ThisDataArc.GUI_DataArc = Object.GUI_DataArc(ObjectHandle) Avatar = ThisDataArc\Avatar Case GUI_OBJECTTYPE_TEXT ThisText.GUI_Text = Object.GUI_Text(ObjectHandle) Avatar = ThisText\Avatar Case GUI_OBJECTTYPE_SPRITE ThisSprite.GUI_Sprite = Object.GUI_Sprite(ObjectHandle) Avatar = ThisSprite\Avatar End Select Return Avatar End Function Some of my functions, like "set value" need a case statement in them like this to handle the different object types. Others however, like a function to position the object, just call this function for whatever object is passed to them and then operate on the entity. It's not perfect but it does allow me to have one set of funcitons to position and set the properties of any GUI object, without having to have all properties that all objects may use contained in one huge type. Of course, is it worthwhile to muck up your code in this way just so that you don't have one huge type that encapsulates all possible objects? I dunno. It saves ram of course, but most games will have so few objects that it's not even remotely worth concerning yourself about. The types are a little cleaner, but the rest of the code tends to be more difficult to understand because of all the case statements. And just having all the objects in one type would not get rid of all case statements, because a databar and a dataarc both need different code to execute when their appearance changes, because their meshes are constructed differently. So you'll still have some case statements in there. All in all, I'm not convinced it was worthwhile to do. It took more time to implement, is more prone to bugs, and doesn't result in simpler, more easily maintained code. But it made me feel good to get it working at the time anyhow. The only situation where I could truly reccomend this is a VERY large and complex project, perferably one with more than one programmer working on the same code. For 90% of Blitz games I just don't think there's a significant benefit to using this method... if any benefit at all. |
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| Another way (I know not exactly what you're after, but it's simple) type player field gfx end type type enemy field gfx end type e.enemy = new enemy p.player = new player movegfx(e\gfx) movegfx(p\gfx) function movegfx(gfxhandle) positionEntity gfxhandle,10,10,10 end function |
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| sswift, Thanks for your detailed solution, actually I have tried something similar, but just got sooo tired of all those damn CASE-lists, that made med think: so I really save time doing it like that?, anyways thanks for your help. Odfex, I have been thinking about it, and I think I go for your solution, but then there is the risk of having to derrive alot of type-"fields" before sending them to a function. On the other hand, making the functions "stupid", by not containing any type-code, can also have its benefits. Well, Thank you very much. Thanks guys, Best regards, Jesper |
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| Well, if they have common components you can break them apart into three types: Type Player field gfx field o.obj end type Type Enemy field gfx field o.obj end type Type obj field x#,dx# field y#,dy# end type This way for movement and the like you just pass the "obj" to the function rather than what the object is |
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| _skully, could you please show how you would create a player then? I mean how do you then access the o.obj? I do not think you can write: Player\o\x#,dx# for example.. else, please prove me wrong :-) Best regards, JEsper |
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| _skully, Correction, correction, I DID find out the syntax. Thanks for your solution to the problem. Best regards, Jesper |
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