State Check Smart Contract function modifiers

States.sol

contract StateMachine {
    enum Stages {
        AcceptingBlindedBids,
        RevealBids,
        AnotherStage,
        AreWeDoneYet,
        Finished
    }
    // This is the current stage.
    Stages public stage = Stages.AcceptingBlindedBids;

    uint public creationTime = now;

    modifier atStage(Stages _stage) {
        if (stage != _stage) throw;
        _
    }
    function nextStage() internal {
        stage = Stages(uint(stage) + 1);
    }
    // Perform timed transitions. Be sure to mention
    // this modifier first, otherwise the guards
    // will not take the new stage into account.
    modifier timedTransitions() {
        if (stage == Stages.AcceptingBlindedBids &&
                    now >= creationTime + 10 days)
            nextStage();
        if (stage == Stages.RevealBids &&
                now >= creationTime + 12 days)
            nextStage();
        // The other stages transition by transaction
    }
    
    // Order of the modifiers matters here!
    function bid()
        timedTransitions
        atStage(Stages.AcceptingBlindedBids)
    {
        // We will not implement that here
    }
    function reveal()
        timedTransitions
        atStage(Stages.RevealBids)
    {
    }

    // This modifier goes to the next stage
    // after the function is done.
    // If you use `return` in the function,
    // `nextStage` will not be called
    // automatically.
    modifier transitionNext()
    {
        _
        nextStage();
    }
    function g()
        timedTransitions
        atStage(Stages.AnotherStage)
        transitionNext
    {
        // If you want to use `return` here,
        // you have to call `nextStage()` manually.
    }
    function h()
        timedTransitions
        atStage(Stages.AreWeDoneYet)
        transitionNext
    {
    }
    function i()
        timedTransitions
        atStage(Stages.Finished)
    {
    }
}