EllanJiang/GameFramework · error · GameFrameworkException

State type ' ' is invalid.

Error message

State type '{0}' is invalid.

What it means

Fsm.Start(Type) throws this when the given type does not derive from FsmState<T>, the required state base class for this FSM's owner type. Start only accepts valid state types of the matching owner type.

Solutions

  1. Make the state class derive from FsmState<T> with the same owner type T as the FSM
  2. Use the strongly typed Start<TState>() overload so the compiler enforces the base class
  3. Fix the owner type T used in Fsm.Create/AddFsm if states were written for a different owner

Example fix

// before
fsm.Start(typeof(SomeClass)); // not an FsmState<T>
// after
public class SomeClass : FsmState<FsmOwner> { }
fsm.Start(typeof(SomeClass));
Defensive patterns

Strategy: type-guard

Validate before calling

if (stateType == null || !typeof(FsmState<T>).IsAssignableFrom(stateType))
    throw new ArgumentException("Type must derive from FsmState<T>");
fsm.Start(stateType);

Type guard

bool IsStateOfType<TOwner>(Type t) => t != null && typeof(FsmState<TOwner>).IsAssignableFrom(t);

Try / catch

try { fsm.Start(stateType); }
catch (GameFrameworkException ex) { Log.Error("State type {0} is not a valid FsmState<T>", stateType?.FullName); }

Prevention

When it happens

Trigger: Passing a Type that is not a subclass of FsmState<T> to Start(Type), e.g. a state registered for a different owner type FsmState<OtherOwner>, an unrelated class, or an interface.

Common situations: Mixing states from two FSMs with different owner types; using the wrong T generic parameter when creating the FSM; config-driven startup resolving a type name that points at the wrong class after a refactor.

Understand the failure class

Background: Type mismatch errors: IllegalArgumentException, TypeError and type guards across 150 open-source libraries — this error's family across 150 libraries.

Related errors

AI-assisted analysis of EllanJiang/GameFramework@d0c010b051 (2026-09-15). Data as JSON: /api/errors/30e6fa797fb53a95. Report an issue: GitHub.

Appendix: source

Thrown at GameFramework/Fsm/Fsm.cs:292

        /// <summary>
        /// 开始有限状态机。
        /// </summary>
        /// <param name="stateType">要开始的有限状态机状态类型。</param>
        public void Start(Type stateType)
        {
            if (IsRunning)
            {
                throw new GameFrameworkException("FSM is running, can not start again.");
            }

            if (stateType == null)
            {
                throw new GameFrameworkException("State type is invalid.");
            }

            if (!typeof(FsmState<T>).IsAssignableFrom(stateType))
            {
                throw new GameFrameworkException(Utility.Text.Format("State type '{0}' is invalid.", stateType.FullName));
            }

            FsmState<T> state = GetState(stateType);
            if (state == null)
            {
                throw new GameFrameworkException(Utility.Text.Format("FSM '{0}' can not start state '{1}' which is not exist.", new TypeNamePair(typeof(T), Name), stateType.FullName));
            }

            m_CurrentStateTime = 0f;
            m_CurrentState = state;
            m_CurrentState.OnEnter(this);
        }

        /// <summary>
        /// 是否存在有限状态机状态。
        /// </summary>
        /// <typeparam name="TState">要检查的有限状态机状态类型。</typeparam>
        /// <returns>是否存在有限状态机状态。</returns>

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