The first edition won the JOLT Award for "Best Technical Book". Based on the content structure of the first three editions, the fourth edition adds content about new features and best practices in Rails. This book starts with the step-by-step creation of a real application and then introduces the built-in functionality of Rails. The book is divided into three parts. The first part introduces the installation of Rails, application verification, the architecture of the Rails framework, and the knowledge of Ruby language; the second part uses an iterative method to create applications, and then builds test cases according to the agile development model, and finally uses capistrano completes the deployment; the third part methodically fills in the missing knowledge and covers enough to cope with daily practical work. This book has both intuitive examples and in-depth analysis. It also covers all aspects of relevant knowledge in web application development. It can be called a comprehensive and easy-to-understand masterpiece.