Book Image

Opa Application Development

By : Li Wenbo
Book Image

Opa Application Development

By: Li Wenbo

Overview of this book

Opa is a full-stack Open Source web development framework for JavaScript that lets you write secure and scalable web applications. It generates standard Node.js/MongoDB applications, natively supports HTML5 and CSS and automates many aspects of modern web application programming. It handles all aspects of web programming written in one consistent language and compiled to web standards.Opa Application Development is a practical,hands-on guide that provides you with a number of step-by-step exercises. It covers almost all aspects of developing a web application with Opa, which will help you take advantage of the real power of Opa, as well as building a secure, powerful web application rapidly.Opa Application Development dives into all concepts and components required to build a web application with Opa. The first half of this book shows you all of the basic building blocks that you will need to develop an Opa application, including the syntax of Opa, web development aspects, client and server communication and slicing, plugin, database, and so on. By the end of the book you will have yourself created a complete web application along with a game: Pacman!
Table of Contents (18 chapters)
Opa Application Development
About the Author
About the Reviewers

Authorizing a user

In this section, we will discuss how to make a simple sign in and sign out system that is an essential part of this forum and a subset of functionality that is frequently needed for other types of websites as well.

Signing in and signing out

For simplicity, we do not provide a sign up process for the application. Users who input a non-blank username and password can log in to the system. Model.auth returns {none} if authorization fails, otherwise it returns {user}, where user is a value of type User.t containing information about the current user. Only signed in users will be able to create topics and post messages. This section will show you what you should do when users sign in. The following code fragment demonstrates the sign in, the code can be found in the login.opa file:

type Login.user = {unlogged} or {User.t user}
state = UserContext.make(Login.user {unlogged})
function login(_) {
username = Dom.get_value(#username)
  password = Dom.get_value(#password)