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POSingleton & Inheritance C#
 

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  1. POSingleton & Inheritance C#
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    <p>First i'll just state that I'm using singletons that won't actually be around throughout the entire app life time. It's more a way of encapsulating what is going on from the user.</p> <p>I have several GameStates, eg InGame or MainMenu, and these have some quite similar function calls so I thought to use inheritence to stop copy / pasting. The following code is what I have, but it does not work as I intend. Here it is:</p> <p>BaseState.cs</p> <pre><code>abstract class BaseState { protected static BaseState mHandle = null; protected static BaseState Handle { get { return mHandle; } set { mHandle = value; } } public static GameState UpdateState(GameTime gameTime) { GameState g = GameState.MainMenu; try { Handle.Update(gameTime); } catch (Exception e) { } return g; } public static void DrawState(GameTime gameTime, SpriteBatch spriteBatch) { Handle.Draw(gameTime, spriteBatch); } public static void Release() { mHandle = null; } protected abstract GameState Update(GameTime gameTime); protected abstract void Draw(GameTime gameTime, SpriteBatch spriteBatch); } </code></pre> <p>InGame.cs</p> <pre><code>class InGame : BaseState { private InGame() { } protected static new BaseState Handle { get { if (mHandle == null) { mHandle = new InGame(); } return mHandle; } set { mHandle = value; } } protected override GameState Update(GameTime gameTime) { return GameState.Quit; } protected override void Draw(GameTime gameTime, SpriteBatch spriteBatch) { } } </code></pre> <p>You can probably tell that I want to be able to use the <code>get</code> and <code>set</code> of <code>InGame</code> in the <code>BaseState</code> so I can simply call Handle.Update() and no matter if I called it from InGame or Menu or whatever it would know which code to use.</p> <p>Obviously I need to brush up on my OO skills. But if anyone could suggest a way to get this to do what I would like it to, or to suggest a different way of going about it I would be grateful. Thanks.</p>
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    1. USLuke
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    1. COWhere is GameState defined ? And you have to make a function virtual to be able to call it from a base class, but trigger derived class behavior (polymorphism). So your setter/getter should be virtual. Also, InGame.Update simply returns GameState.Quit, was that intended ?
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      1. USJulien Lebot
    2. COGameState is a simple enum. Yes it returns GameState.Quit intentionally for now They can't be virtual as they are static, the two are opposites of each other I think? It gives compile errors at least; I tried the `new` keyword as it seemed like it's what I wanted and it compiled. Didn't do what I expect though.
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    3. COI don't think you need a Singleton in your case, but plain and simple polymorphism. A singleton implies only one instance of a type can exist at any point, but in your case I believe multiple states can co-exist. Think about it, when you go from the game state to the menu state and back, you don't expect your game instance to be destroyed, but with a singleton you would have to.
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