Building complex UIs with Vue
Tags: vue, xstate, statemachines, ui
Published: 2023-11-09 15:52:55

Ah, the joy of coding UIs: Where v-if labyrinths and switch mazes are just part of the daily puzzle. Just when you've smoothed out all the kinks, along comes an edge case, turning your neatly organized code into a mystery worthy of a detective novel.

Wouldn't it be something if we could anticipate these twists in the plot? State machines offer us a way to do just that. They're the understated heroes, ensuring that no matter how the story unfolds, each part of your application plays its role seamlessly.

As we set the stage to explore this concept further, remember: the right tools can turn even the most complex state logic into a narrative that's easy to follow and even easier to manage.



## Introduction.

In the quest to handle the myriad of user interactions, traditional approaches often lead us down a rabbit hole of nested if statements, switch cases, and numerous v-if directives. While these tools are essential in our developer toolkit, they can become unwieldy as the complexity of our application's UI grows. Each new user action or data change potentially adds another branch to our already tangled decision tree.

State machines introduce a different philosophy: rather than reacting to changes with conditional logic that needs to constantly check "What state am I in? What should I do now?", we define a finite set of states and the rules for transitioning between them upfront. Each state is an explicit representation of the UI with a defined set of possible transitions, reducing the chance of unexpected behavior.

Here's the kicker: state machines enforce a one-way ticket from one state to another. There's no jumping around or skipping steps. If the user does X, the UI reliably moves to state Y. It's declarative; it's deterministic. This means we can look at our UI's model and predict exactly how it will behave in any given state, which is something akin to having a crystal ball in the world of UI development.

So, as we embrace the discipline of state machines, we're not just coding; we're "architecting" our UI's behavior with precision. In the next section, we'll unpack how this looks in practice and why XState can be your ally in this architectural endeavor.



## What tools do you need?

In the Vue.js ecosystem, state management often revolves around Vuex or the Composition API, each with its own approach to handling reactive data and state. XState enters this scene as a state management solution that emphasizes predictability and maintainability, particularly for complex logic scenarios.

### How XState Complements Vue's Reactive Nature

Vue’s reactivity system is designed to update the UI in response to state changes. XState complements this by providing a finite state machine or statecharts mechanism to model application states. This partnership means Vue takes care of rendering and re-rendering components based on state changes that XState manages with precision.

First, we set up XState with Vue by installing the XState library:

```
npm install xstate
```

Then, we create a machine definition. For instance, if we're dealing with a document, our machine might look like this:


![Creation of the state machine](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/8l4ntx9raov3k4p49ekk.png)

In this documentMachine:

`inactive`: The state where no document is open; the application is not active.

`viewing`: A document is open for viewing; no editing is occurring.

`editing`: The document is currently being edited.


### Reactive Current State

In our Vue component, we can use the Composition API to make the current state of the machine reactive:


![Consumption and usage of the state machine](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/yhro78x0osrl5t6szsk5.png)


## Considerations for Using XState in Vue.js Applications.

### - When to Use XState

XState is most beneficial when your application faces complex state management challenges. Scenarios where multiple states interrelate with various events, side effects, and asynchronous processes are where XState truly shines. It's particularly advantageous when:

- You need to manage long-running processes like user authentication or payment flows.
- Your UI logic depends on multiple events and user interactions that could lead to a high number of possible states.
- You want to ensure a clear separation of concerns, making your code more maintainable and testable.

### - The Learning Curve

While the structured approach to state management that XState brings to the table is powerful, it does come with a learning curve. Developers accustomed to Vue's reactivity system may need some time to adapt to thinking in terms of finite state machines.

Here's a nuanced take:

For straightforward applications with simple state logic, the overhead of learning and implementing XState might not immediately pay off.

In contrast, for applications with complex state interactions or those that require future scaling, investing in learning XState can save considerable time and prevent bugs in the long run.

### - Embracing the Paradigm Shift

Adopting XState isn't just about learning a new library—it's about embracing a paradigm shift in how you handle state within your applications. This means:

Moving away from imperative checks and mutations to a more declarative state transition system.

Thinking about states in terms of possible events and transitions rather than just the current condition of the UI.



## Conclusion

Integrating XState into your Vue.js workflow is a strategic decision. It offers a robust solution for complex state management but requires a willingness to learn its principles. As with any technology, consider your project's specific needs and whether the benefits align with your goals. With XState, you're not just adding a library, but adopting a methodology that could lead to more predictable, maintainable, and scalable applications.