Book Image

.Go Programming Blueprints - Second Edition

By : Mat Ryer
Book Image

.Go Programming Blueprints - Second Edition

By: Mat Ryer

Overview of this book

Go is the language of the Internet age, and the latest version of Go comes with major architectural changes. Implementation of the language, runtime, and libraries has changed significantly. The compiler and runtime are now written entirely in Go. The garbage collector is now concurrent and provides dramatically lower pause times by running in parallel with other Go routines when possible. This book will show you how to leverage all the latest features and much more. This book shows you how to build powerful systems and drops you into real-world situations. You will learn to develop high quality command-line tools that utilize the powerful shell capabilities and perform well using Go's in-built concurrency mechanisms. Scale, performance, and high availability lie at the heart of our projects, and the lessons learned throughout this book will arm you with everything you need to build world-class solutions. You will get a feel for app deployment using Docker and Google App Engine. Each project could form the basis of a start-up, which means they are directly applicable to modern software markets.
Table of Contents (19 chapters)
Go Programming Blueprints Second Edition
Credits
About the Author
Acknowledgments
About the Reviewer
www.PacktPub.com
Preface

Combining all three implementations


To close this chapter with a bang, we will implement a mechanism in which each Avatar implementation takes a turn in trying to get a URL for a user. If the first implementation returns the ErrNoAvatarURL error, we will try the next and so on until we find a useable value.

In avatar.go, underneath the Avatar type, add the following type definition:

type TryAvatars []Avatar 

The TryAvatars type is simply a slice of Avatar objects that we are free to add methods to. Let's add the following GetAvatarURL method:

func (a TryAvatars) GetAvatarURL(u ChatUser) (string, error) { 
  for _, avatar := range a { 
    if url, err := avatar.GetAvatarURL(u); err == nil { 
      return url, nil 
    } 
  } 
  return "", ErrNoAvatarURL 
} 

This means that TryAvatars is now a valid Avatar implementation and can be used in place of any specific implementation. In the preceding method, we iterated over the slice of Avatar objects in...