Introduction to the newline guide to building a React App with MobX State Tree

Application Overview

State Management on the JavaScript ecosystem

State Management

What is MobX State Tree?

What will you learn in this course?

Will this course be for you?

Introduction

Introduction to the mental model of MobX State Tree

The Tree in MobX State Tree

Introduction to the store model of MobX State Tree

The Store Model

Introduction to the types in MobX State Tree

Types

Introduction to the model actions of MobX State Tree

Model Actions

Introduction to the model views of MobX State Tree

Model Views

Introduction to the store snapshots of MobX State Tree

Snapshots

Identifiers and references of MobX State Tree

Identifiers and References

Asynchronous Actions

Lifecycle Hooks

Concepts

Arrays in MobX State Tree

Maps

Working with nested stores in MobX State Tree

Nesting Stores

Optimistic Updates

Time Travel

Advanced Concepts

Overview of React and MobX State Tree

Combining MobX State Tree with React via Context and a custom Hook

Context and Hooks

Observable

React

Overview

Building Voyager

mobx-state-tree

In this course, we will create a complete React Application with the state management handled by MobX State Tree, a state container system that is built on MobX, a functional reactive state library.

MobX State Tree will give your application a solid structure and foundation for large-scale applications and for small applications that are expected to scale rapidly. In comparison to Redux, MobX State Tree outstands it in performance with much less boilerplate. MobX is one of the most popular Redux alternatives and it's used by companies all over the world, including Netflix, Grow, IBM, DAZN, Baidu, and more.

During this course, you'll learn:

* Types in MobX State Tree.
* How to create the architecture of a centralized store.
* How to mutate the state via actions that could be asynchronous or not, depending on if we need to perform network requests to persist data into a database via GraphQL.
* Understanding snapshots and how we can benefit from them to time-travel if a network request fails.
* Understanding how MobX State Tree makes use of observable properties and observers.
* Leveraging re-renders in your React Application to MobX observers for better performance optimizations.

By the end of this course, you will have the knowledge and skills that it takes to build a real-world, production-level React Application with a State Management with top-notch performance that can scale with ease.

In this course, we'll show you how to build a React App with MobX State Tree.

The newline Guide to Building a React App with MobX State Tree

How to integrate MobX State Tree within your React App

Dealing with asynchronous flows and time travel to preserve state on networking errors

How to create a scalable store using MobX State Tree

---
title: Model Views
slug: model-views-in-mobx-state-tree
description: Introduction to the model views of MobX State Tree
role: "LESSON"
isPublicLesson: false
---

# Model Views in MobX State Tree

Anything that can be derived from your state in MobX State Tree is called a "view" or "derivation".

There are two types of views:

1.  With arguments.
2.  Without arguments.

The latter (2) are called **computed values**, based on the [computed](https://mobx.js.org/refguide/computed-decorator.html) concept in MobX. Don't worry if you don't understand this right now, because we will see a quick example that will make it click in your mind easily.

## Defining views

```js { actualFilename=src/views.js endChar=679 endLine=33 startChar=0 startLine=1 statedFilename=src/views.js url=https&#x3A;//gitlab.com/fullstackio/books/newline-guide-to-building-a-react-app-with-mobx-state-tree/module_01/lesson_01.05/src/views.js }
import { types } from "mobx-state-tree";

const User = types
  .model("User", {
    name: types.string,
    lastName: "Casillas",
    age: types.number,
  })
  // 1
  .views((self) => ({
    // 2
    get fullName() {
      return `${self.name} ${self.lastName}`;
    },
  }));

const RootStore = types
  .model("RootStore", {
    users: types.array(User), // 3
  })
  .views((self) => ({
    // 4
    usersOlderThan(age) {
      return self.users.filter((user) => user.age > age);
    },
    usersYoungerThan(age) {
      return self.users.filter((user) => user.age < age);
    },
    usersWithAge(age) {
      return self.users.filter((user) => user.age === age);
    },
  }));
```

Let's explain the code above. As we can see, we now have two separate stores:

1.  `User` that was returned from `types.model`.
2.  `RootStore` that was returned from `types.model` and is going to be used as the main entry point of our state tree.

Now let's get into detail going by the numbered lines we've marked on your code:

1.  `views` method call takes a function. In this case, `self` is the main and only argument to that function and references the model itself, allowing you to access its properties and other views and actions within this scope, and returning an object literal that contains all of the views that have been created for this model.
2.  Defining a view (function) called `fullName` without arguments will turn this view into a computed property and you'll be able to access it as if you were just accessing a regular property from an object: `User.fullName`.
3.  In this step, we're defining a property for the `RootStore` called users, which is going to be an array of `User` store. This means that through `RootStore.users`, we will have access to all of the properties and views and actions of each user that we store within this array.
4.  `usersOlderThan(age)` is a view that will take a number and return a list of users that are older than the given age.

As per the example above, views are extremely useful because you can generate computed properties that will always be automatically up-to-date with the latest data from your store. This is one of the key benefits of MobX State Tree and MobX.
