C# generics, cross referencing classes for state pattern -

i trying c# generics , have created state machine state pattern , try refactor.

i have state, has reference object it's working on.

public abstract class abstractstate<t> t : statefulobject {      protected t statefulobject;      public abstractstate(t statefulobject) {         this.statefulobject = statefulobject;     }  } 

and have object has states, should have reference current state.

public abstract class statefulobject<t> : monobehaviour t : abstractstate<statefulobject<t>> {      public t state;  } 

but not work ("the type cannot used type parameter 't' in generic type or method").

what want achieve :

public class monster : statefulobject<monsterstate> {  }  public abstract class monsterstate : abstractstate<monster> {  } 

is possible? if it's not way, there another? thx.

you can abuse interfaces , variance achieve that:

public interface istate<out tobject, in tstate>     tobject : istatefulobject<tobject, tstate>     tstate : istate<tobject, tstate> { }  public interface istatefulobject<in tobject, out tstate>     tobject : istatefulobject<tobject, tstate>     tstate : istate<tobject, tstate> { }  public abstract class abstractstate<tobject> : istate<tobject, abstractstate<tobject>>     tobject : istatefulobject<tobject, abstractstate<tobject>> {     protected tobject object { get; private set; }      public abstractstate(tobject obj)     {         object = obj;     } }  public abstract class statefulobject<tstate> : istatefulobject<statefulobject<tstate>, tstate>     tstate : istate<statefulobject<tstate>, tstate> {     protected tstate state { get; set; } }  public class monster : statefulobject<monsterstate> {     public monster()     {         state = new idlemonsterstate(this);     } }  public abstract class monsterstate : abstractstate<monster> {     protected monsterstate(monster monster)         : base(monster)     {     } }  public class idlemonsterstate : monsterstate {     public idlemonsterstate(monster monster)         : base(monster)     {     } } 

whether it's idea dubious, such code may confusing.

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you go simpler (but less strongly-typed) approach:

public abstract class abstractstate { }  public abstract class statefulobject { }  public abstract class abstractstate<tobject> : abstractstate     tobject : statefulobject {     protected tobject object { get; private set; }      public abstractstate(tobject obj)     {         object = obj;     } }  public abstract class statefulobject<tstate> : statefulobject     tstate : abstractstate {     protected tstate state { get; set; } }  public class monster : statefulobject<monsterstate> { }  public abstract class monsterstate : abstractstate<monster> {     protected monsterstate(monster monster)         : base(monster)     {     } } 

this won't ensure won't able assign, playerstate monster, should check @ runtime.