When to use state Design pattern?
State design pattern is used when an Object changes its behavior based on its internal state. If we have to change behavior of an object based on its state, we can have a state variable in the Object and use if-else condition block to perform different actions based on the state.
How to use state pattern?
In State pattern, we create objects which represent various states and a context object whose behavior varies as its state object changes.
- Implementation.
- Create an interface.
- Create concrete classes implementing the same interface.
- Create Context Class.
- Use the Context to see change in behaviour when State changes.
How can you tell if a state transition is invalid?
You can use State Table to determine invalid system transitions. In a State Table, all the valid states are listed on the left side of the table, and the events that cause them on the top. Each cell represents the state system will move to when the corresponding event occurs.
How are states represented in a state transition diagram?
Two main ways to represent or design state transition, State transition diagram, and State transition table. In state transition diagram the states are shown in boxed texts, and the transition is represented by arrows. In state transition table all the states are listed on the left side, and the events are described on the top.
Why do we need a state machine design pattern?
In the last post, we talked about using State Machine to build state-oriented systems to solve several business problems. Before we start building any proper state machine example, it’s better if we explore other alternatives & discuss their pros & cons. It will help us to properly realise the potential of State Machine design patterns.
Why do we need different transitions in state machine?
Since state machine is data driven, depending on different data/input parameter, your product team might ask you to execute different transitions from the same state. So this kind of requirements can cause having several transitions with messy precondition check. It completely depends on the product & the current implementation of the machine.