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

Database manipulation

We can manipulate data through database paths. The following piece of code declares a testdb database and defines several paths:

type Student = {int id, string name, int age}
database testdb {
    int               /basic/i     //Basic type int
    float             /basic/f     //Basic type float
    string            /basic/s     //Basic type string
    Student           /stu         //Record
    list(string)      /lst         //List
    intmap(Student)   /stumap      //Map
    Student           /stuset[{id}]     //Set

Type student that we defined ourselves. In addition to this type, our example covers the datatypes that are most frequently used in databases.

Each database path has a default value. Whenever we attempt to read a value that does not exist (either because it was never initialized or it has been removed), the default value is returned. The following list shows the default values for different types:

  • The default value for an integer (int) is 0

  • The default...