Validation Setup in Firebase

1. Introduction

In this tutorial, we will be learning about setting up data validation in Firebase. We'll define validation rules to ensure the data being sent to our database meets certain criteria.

By the end of this tutorial, you will be able to:

• Understand what data validation is and why it is important.
• Set up validation rules in Firebase.
• Test your validation rules to ensure they work as expected.

Prerequisites:

• Basic knowledge of JavaScript.
• Familiarity with Firebase and its database (Firestore or Realtime Database).
• A Firebase project to work with.

2. Step-by-Step Guide

Data validation is a crucial part of any application. It ensures that only valid data gets stored in your database. In Firebase, we use security rules to validate data.

Firebase Security Rules:

Firebase Security Rules stand between your data and malicious users. They can validate the shape and size of your data, as well as authenticate users.

Setting Up Validation Rules:

In Firebase, you can write security rules in the Firebase console, under the 'Rules' tab of the Database section. You can also write and deploy them from the Firebase CLI.

Here's a basic example of what a Firebase rule looks like:

{
  "rules": {
    ".read": "auth != null",
    ".write": "auth != null"
  }
}

This rule ensures that only authenticated users can read or write data.

Best Practices:

• Always test your rules in the Firebase Emulator Suite before deploying them.
• Keep your rules as specific as possible.
• Use Firebase Admin SDK to bypass these rules when necessary.

3. Code Examples

Example 1:

Validating the structure of a document in Firestore:

{
  "rules": {
    "users": {
      "$uid": {
        ".read": "auth != null && auth.uid == $uid",
        ".write": "auth != null && auth.uid == $uid",
        "name": { ".validate": "newData.isString()" },
        "age": { ".validate": "newData.isNumber() && newData.val() >= 18" }
      }
    }
  }
}

In this example, we are validating that the name field is a string and the age field is a number greater than or equal to 18.

Example 2:

Limiting the size of a document or field in Firestore:

{
  "rules": {
    "posts": {
      "$postId": {
        ".write": "auth != null",
        ".validate": "newData.hasChildren(['title', 'body']) && newData.child('body').isString() && newData.child('body').val().length <= 500"
      }
    }
  }
}

In this example, we are ensuring that a post has a title and a body, and that the body does not exceed 500 characters.

4. Summary

In this tutorial, we learned about data validation and how to set up validation rules in Firebase. Firebase security rules are versatile and powerful, allowing us to perform complex validations.

To further your learning, you can:

• Learn more about Firestore Security Rules in the Firebase Documentation.
• Practice writing and testing your own validation rules.

5. Practice Exercises

Exercise 1:

Write a validation rule that allows a user to write to their own profile, but not to others.

Solution:

{
  "rules": {
    "users": {
      "$uid": {
        ".write": "auth != null && auth.uid == $uid"
      }
    }
  }
}

Exercise 2:

Write a validation rule that ensures a post document has a title, body, and authorId, and that the title does not exceed 100 characters.

Solution:

{
  "rules": {
    "posts": {
      "$postId": {
        ".write": "auth != null",
        ".validate": "newData.hasChildren(['title', 'body', 'authorId']) && newData.child('title').isString() && newData.child('title').val().length <= 100"
      }
    }
  }
}

Try creating more complex validation rules, such as ones that involve multiple fields or more complex data types.