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6375 :: Inheritance vs composition

• mantielero (orginal) [2020-05-24T19:47:46+02:00] view original

  With all this experiments with OOP, I have read in several places that Nim encourage composition against inheritance. I have read this which is very clear, but I don't know how this translates well into Nim. The inheritance is pretty clear to me, thanks to previous posts. It is more the composition bit.

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• Stefan_Salewski (orginal) [2020-05-24T20:23:16+02:00] view original

  Composition is more flexible than inheritance. You can put many objects into another object with composition, while with inheritance you only subclass. Note that another option are the sum types, also called ADT or objects variants. They can have advantages for performance, as you can have value types in a seq then, also mentioned in my book.

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• mantielero (orginal) [2020-05-24T20:46:52+02:00] view original

  Ahhh. I though it would be something more complicated. It is just a matter of adding objects into another object.

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• cantanima (orginal) [2020-05-25T14:57:56+02:00] view original

  That can be done in a lot of languages (I first saw it in Eiffel), but then you have a Dog that can't poop(), and that causes problems.

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• Pixeye (orginal) [2020-05-26T07:22:53+02:00] view original

  use best of two worlds! Those are only concepts and tools in your work. I usually prefer using simple inheritance no more then 1-2 level deep and totally fine and ok with it. Basically it's good for thin abstraction layer, implementing really common and basic routines.

  
  UIButton  -> UIButtonUpgrade
  UIButton  -> UIButtonConfirm
  UIMenu -> UIMenuSkills
  Run

  Composition requires more mental work and planning. I'm writing a game on ecs and we have more than 60 components right now ( in C# ) and average setup for an object looks like this

  protected override void Setup()
      {
        entity.Set(tags.ally);
        
        var cobject     = entity.Set<ComponentObject>();
        var cmotion    = entity.Set<ComponentMotion>();
        var canimator = entity.Set<ComponentAnimator>();
        var crender     = entity.Set<ComponentRender>();
        var ccollider   = entity.Set<ComponentCollider>();
        var cplayer     = entity.Set<ComponentPlayer>();
        var chealth     = entity.Set<ComponentHealth>();
        var carea        = entity.Set<ComponentArea>();
        
        //// Weapon
        cplayer.weapon.source          = db.weapon[db.weapons.gun];
        cplayer.weapon.muzzle         = math.pixels3(29, -3, 0);
        cplayer.weapon.clip               = 16;
  Run

  Personally I DO prefer composition over inheritance but preferring is not versus, it's that I use composition for the most tasks and it took time for this mind shift.

  So compositions aspects :

  • you need plan more and carefully
  • you will often write more code then with inheritance
  • sometimes the code is more abstract
  • it's harder in the beginning of the project
  • your code will become more modular and flexible ( while its preferable in the most cases sometimes you don't care )
  • easier to refactor
  • easier to toy around, remove, add new parts without breaking the project

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• Pixeye (orginal) [2020-05-26T07:42:30+02:00] view original

  Nim. Nim is puuuuurrrrfect for all of this stuff. Really. Every day I cry for joy after finding this language. It reduces so much noise and boilerplate for me.

  I've already implemented my c# ecs in nim ( and it took way less work ) and my workflow looks like this:

  type ComponentHealth = object
    val: int
  type ComponentAI = object
  type ComponentBurning = object
  type ComponentAnimal = object
  type TagAlpaca = object
  
  ecs.add ComponentHealth
  ecs.add ComponentAI
  ecs.add ComponentBurning
  ecs.add ComponentAnimal
  
  proc newAnimal(): ent
    result = entity()
    result.add ComponentHealth
    result.add ComponentAI
    result.add ComponentBurning
    result.add ComponentAnimal
  
  var alpaca = newAnimal()
  alpaca.add TagAlpaca
  
  ecs.group burning_animals:
    comps: (ComponentHealth,ComponentAI,ComponentBurning,ComponentAnimal)
  
  app.start:
     echo "blazing"
  
  app.run:
    for entity in burning_animals:
      entity.chealth.val -= 10 * dt
    if input.down escape:
      app.quit()
  
  app.close:
    echo "alpaca"
  Run

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