States

Modified on 2010/12/10 18:37 by John — Categorized as: States

Overview

Workflow classes can define a set of states allowing a workflow object to be in one given state. The workflow changes state by excuting 'enterstate' operator. Operations can be performed upon entering and leaving a state. Instance methods and properties can dynamically change to public or private as the state of the workflow object changes by using the 'states ' construct.


Defining a State

A state is declared in Jetfire as method with no return type. For example:
public workflow MyFlow
{
// declare a state called 'Start'
Start(){}
}

Entering a State

To enter a state the 'enterstate statename() ' operator needs to be used. Until the 'enterstate ' operator is excuted the workflow is in a null state.
public workflow MyFlow
{
// 'Start' state
Start()
{
// place code to be executed when
// the state is entered.
}
// constructor
public MyFlow()
{
enterstate Start()
}
}

Using The 'states' Construct

Using the states construct the access modifier of a method or property can change dynamically as the state of the workflow changes. For example in the following code the method 'Submit' is public when the workflow is in the 'EnterData' state. When the workflow is no longer in the "EnterData" state the 'AddData' method access modifier is private.

private ArrayList dataList = new ArrayList();
//
//method 'AddData' has a dynamic access modifier
//
public void AddData(string data) :states(EnterData)
{
this.dataList.Add(data);
}
State AddData
EnterDatapublic
any other stateprivate


Examples


DVD Library

In this example each DVD in the library is represented by a workflow. The "Borrow" a DVD and "Return" a DVD methods are controlled by the 'states' construct.

Request Approval

This advanced example employs both states and roles in an request approval workflow. The 'state' of workflow ensures once a method is 'approved' that it can not be 'declined' at later date. The roles determine which users can 'approve' the request.