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Methods in my IComponentData struct

Discussion in 'Data Oriented Technology Stack' started by supermoof, Apr 29, 2018.

  1. supermoof

    supermoof

    Joined:
    Sep 24, 2015
    Posts:
    45
    Hello, I'm having trouble trying to get something to work, probably something I don't know about C# so it would be nice to learn from this.

    I have a method in my IComponentData struct, which turns a bool1 to true.

    Example:
    Code (CSharp):
    1.  
    2. public struct Test: IComponentData
    3. {
    4.     public bool1 testBool;
    5.  
    6.     public void MakeTrue()
    7.     {
    8.         testBool = true;
    9.     }
    10. }
    11.  
    So in my system, I have it calling:
    Code (CSharp):
    1.     protected override void OnUpdate()
    2.     {
    3.         for (var i = 0; i < data.Length; i++)
    4.         {
    5.             data.Test[i].MakeTrue();
    6.             Debug.Log(data.Test[i].testBool);
    7.         }
    8.     }
    but it doesn't seem to work, still returns false. If anyone can lecture me on why this doesn't work, it would be awesome :)
     
  2. tertle

    tertle

    Joined:
    Jan 25, 2011
    Posts:
    1,722
    It's late, I'm tired and lying in bed but I think the problem is you're misunderstanding how structs work.

    Structs are copied so if you break it up this is what you're code is doing is

    Code (CSharp):
    1.             var test = data.Test[i];
    2.             test.MakeTrue();
    3.             Debug.Log(data.Test[i].testBool); // false
    4.             Debug.Log(test.testBool); // true
    To get the behaviour you want you have to apply it back.

    Code (CSharp):
    1.             var test = data.Test[i];
    2.             test.MakeTrue();
    3.             data.Test[i]  = test;
    4.             Debug.Log(data.Test[i].testBool); // true
    This is why mutable structs are considered evil and something you should avoid in general
     
    supermoof likes this.
  3. supermoof

    supermoof

    Joined:
    Sep 24, 2015
    Posts:
    45
    Thank you! Yeah, it was just my misunderstanding on how structs work. If mutable structs should be avoided, as an alternative solution, if I want my values to be changed through a method, should I use a monobehaviour instead?
     
    Last edited: Apr 29, 2018
  4. Kender

    Kender

    Joined:
    Nov 16, 2012
    Posts:
    163
    You shouldn't have any methods in your components. Use systems only
     
  5. supermoof

    supermoof

    Joined:
    Sep 24, 2015
    Posts:
    45
    So instead of having a method in my struct, for example, changing 3 booleans to true, I would have the method in my system change the variables instead.

    Like this?
    Code (CSharp):
    1.     void Test(int index)
    2.     {
    3.         Test t = data.Test[index];
    4.         t.testBool1 = true;
    5.         t.testBool2 = true;
    6.         t.testBool3 = true;
    7.         data.Test[index] = t;
    8.     }
     
  6. Kender

    Kender

    Joined:
    Nov 16, 2012
    Posts:
    163
    Yep. Or you may even not use a separate method - simply embed this code in your struct's loop