create a state machine in swift

To create a state machine in Swift, you can follow the steps below:

1. Define an enumeration to represent the states of the machine.
2. Define the events that can trigger a transition between states.
3. Implement state transition logic using switch statements that handle each state/event combination.
4. Create an instance of the state machine and expose a method to trigger events.

Here's an example of how to implement a simple state machine in Swift:

main.swift
enum State {
    case idle
    case running
    case paused
    case stopped
}

enum Event {
    case start
    case pause
    case resume
    case stop
}

class StateMachine {
    private var state: State = .idle
    
    func trigger(event: Event) {
        switch (state, event) {
        case (.idle, .start):
            state = .running
            print("Machine is now running")
        case (.running, .pause):
            state = .paused
            print("Machine is now paused")
        case (.paused, .resume):
            state = .running
            print("Machine has resumed running")
        case (.running, .stop):
            state = .stopped
            print("Machine has stopped")
        default:
            print("Invalid event for current state")
        }
    }
}

// example usage
let machine = StateMachine()

machine.trigger(event: .start) // Machine is now running
machine.trigger(event: .pause) // Machine is now paused
machine.trigger(event: .start) // Invalid event for current state
machine.trigger(event: .resume) // Machine has resumed running
machine.trigger(event: .stop) // Machine has stopped
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In the example above, we define a State enumeration with four possible values: idle, running, paused, and stopped. We also define an Event enumeration with four values that correspond to the different events that can trigger a transition between states. The StateMachine class has a trigger method that uses switch statements to handle each state/event combination and update the current state accordingly. We then create an instance of the StateMachine class and trigger some events to see the state transitions in action.

This is just a simple example of how to implement a state machine in Swift. Depending on the complexity of your application, you may need to use more advanced techniques like hierarchical state machines or state charts to model your state machine.