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How do you organize your business logic with finite-state machines? Here is a brief introduction to the concept applied to e-commerce:

🚦 What is a State Machine?

Imagine an intersection with traffic lights to regulate the passage of cars and pedestrians. The light can be:

– Red 🔴 ⇒ In this state, cars must stop, and pedestrians can cross.

– Yellow 🟡 ⇒ In this state, cars should prepare to stop, and pedestrians should not start crossing.

– Green 🟢 ⇒ In this state, cars can proceed, and pedestrians can't cross.

In a state machine, finite states represent specific conditions and transitions between them must follow a logical sequence. You can't jump directly from 🔴 (stop) to 🟢 (go), or from 🟢 to 🟡 (prepare to stop).

💡 Why Use State Machines?

– Clarity: State machines break down your application into manageable states, making the logic easier to read and understand.

– Reliability: Transitions between states are explicit, which reduces the likelihood of bugs.

– Scalability: Introducing a new feature or state becomes simpler, making your codebase more maintainable.

Actually, finite-state machines are not just for software engineers but a useful framework for thinking about processes and systems.

🛒 A Detailed Example with an E-Commerce Cart

Loading State: When the cart is accessed, it's in a ‘loading' state. Here, an ‘invoke' fetches items 📦 from a service. Upon success, the cart transitions to the ‘idle' state and updates its context (think of it as a mini-store) with the fetched items.

Idle State: Think of ‘idle' as a state of readiness. The cart has finished loading, has its data, and is waiting for the user to initiate events.

 – Actions: When an item is added, removed, or its quantity updated, actions are executed to mutate the context 🔄, thanks to events that trigger these actions. (The event ‘REMOVE_ITEM' triggers the action ‘removeItem' that mutates the context.)

 – Context: The context stores the cart items and a flag to indicate whether the terms and conditions are accepted ✅.

goToCheckout State: To transition to ‘goToCheckout,' a guard condition checks if the terms are accepted 🚫. If yes, the cart moves to this state to complete the purchase 🛍️.

In the end, we can represent all the logic of our cart within a machine in a single place with a formalized and highly deterministic approach. This minimizes side effects. Also, this is just a glimpse of what an FSM can do, followed by parallel state logic, actor model, parent-to-child communication, and so on.

A detailed example of a FSM with an e-commerce cart


September 11, 2023 - 4:32 am

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