Input validation patterns in GraphQL - Mini Project: Build & Apply

Input Validation Patterns in GraphQL

📖 Scenario: You are building a simple GraphQL API for a user registration system. You need to ensure that the inputs for creating a user are valid before saving them to the database.

🎯 Goal: Build a GraphQL schema with input validation patterns for user registration, including checks for username length, email format, and password strength.

📋 What You'll Learn

Create a GraphQL input type called CreateUserInput with fields username, email, and password.

Add validation rules for username to be at least 3 characters long.

Add validation rules for email to match a basic email pattern.

Add validation rules for password to be at least 8 characters long.

Create a mutation createUser that accepts CreateUserInput and returns a User type.

💡 Why This Matters

🌍 Real World

Input validation in GraphQL APIs is essential to prevent invalid or harmful data from entering your system, improving security and data quality.

💼 Career

Many backend developer roles require designing GraphQL schemas with proper input validation to build robust APIs.

1

Define the User type and CreateUserInput input type

Create a GraphQL User type with fields id (ID!), username (String!), email (String!). Then create an input type called CreateUserInput with fields username (String!), email (String!), and password (String!).

GraphQL

type User {
  id: ID!
  username: String!
  email: String!
}

input CreateUserInput {
  username: String!
  email: String!
  password: String!
}

# Your code here

Need a hint?

Define the User type and CreateUserInput input type with the exact fields and types.

2

Add validation directives for username and email

Add validation directives to CreateUserInput: for username, add a directive to enforce minimum length of 3 characters. For email, add a directive to enforce a basic email pattern using a regex.

GraphQL

type User {
  id: ID!
  username: String!
  email: String!
}

input CreateUserInput {
  username: String! @length(min: 3)
  email: String! @pattern(regex: "^[^@\s]+@[^@\s]+\\.[^@\s]+$")
  password: String!
}

# Your code here

Need a hint?

Use directives like @length(min: 3) and @pattern(regex: "...") on the input fields.

3

Add validation directive for password length

Add a validation directive to the password field in CreateUserInput to enforce a minimum length of 8 characters.

GraphQL

type User {
  id: ID!
  username: String!
  email: String!
}

input CreateUserInput {
  username: String! @length(min: 3)
  email: String! @pattern(regex: "^[^@\s]+@[^@\s]+\\.[^@\s]+$")
  password: String! @length(min: 8)
}

# Your code here

Need a hint?

Add @length(min: 8) directive to the password field.

4

Create the createUser mutation

Add a mutation called createUser that accepts an argument input of type CreateUserInput! and returns a User!.

GraphQL

type User {
  id: ID!
  username: String!
  email: String!
}

input CreateUserInput {
  username: String! @length(min: 3)
  email: String! @pattern(regex: "^[^@\s]+@[^@\s]+\\.[^@\s]+$")
  password: String! @length(min: 8)
}

type Mutation {
  createUser(input: CreateUserInput!): User!
}

# Your code here

Need a hint?

Define the Mutation type with the createUser mutation accepting CreateUserInput! and returning User!.