Book Image

Go Design Patterns

By : Mario Castro Contreras
Book Image

Go Design Patterns

By: Mario Castro Contreras

Overview of this book

Go is a multi-paradigm programming language that has built-in facilities to create concurrent applications. Design patterns allow developers to efficiently address common problems faced during developing applications. Go Design Patterns will provide readers with a reference point to software design patterns and CSP concurrency design patterns to help them build applications in a more idiomatic, robust, and convenient way in Go. The book starts with a brief introduction to Go programming essentials and quickly moves on to explain the idea behind the creation of design patterns and how they appeared in the 90’s as a common "language" between developers to solve common tasks in object-oriented programming languages. You will then learn how to apply the 23 Gang of Four (GoF) design patterns in Go and also learn about CSP concurrency patterns, the "killer feature" in Go that has helped Google develop software to maintain thousands of servers. With all of this the book will enable you to understand and apply design patterns in an idiomatic way that will produce concise, readable, and maintainable software.
Table of Contents (17 chapters)
Go Design Patterns
Credits
About the Author
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface

Zero-initialization


Zero-initialization is a source of confusion sometimes. They are default values for many types that are assigned even if you don't provide a value for the definition. Following are the zero-initialization for various types:

  • The false initialization for bool type.

  • Using 0 values for int type.

  • Using 0.0 for float type.

  • Using "" (empty strings) for string type.

  • Using nil keyword for pointers, functions, interfaces, slices, channels and maps.

  • Empty struct for structures without fields.

  • Zero-initialized struct for structures with fields. The zero value of a structure is defined as the structure that has its fields initialized as zero value too.

Zero-initialization is important when programming in Go because you won't be able to return a nil value if you have to return an int type or a struct. Keep this in mind, for example, in functions where you have to return a bool value. Imagine that you want to know if a number is divisible by a different number but you pass 0 (zero) as the divisor.

func main() { 
    res := divisibleBy(10,0) 
    fmt.Printf("%v\n", res) 
} 
 
func divisibleBy(n, divisor int) bool { 
    if divisor == 0 { 
        //You cannot divide by zero 
        return false 
    } 
 
    return (n % divisor == 0) 
} 

The output of this program is false but this is incorrect. A number divided by zero is an error, it's not that 10 isn't divisible by zero but that a number cannot be divided by zero by definition. Zero-initialization is making things awkward in this situation. So, how can we solve this error? Consider the following code:

func main() { 
    res, err := divisibleBy(10,0) 
    if err != nil { 
log.Fatal(err) 
    } 
 
    log.Printf("%v\n", res) 
} 
 
func divisibleBy(n, divisor int) (bool, error) { 
    if divisor == 0 { 
        //You cannot divide by zero 
        return false, errors.New("A number cannot be divided by zero") 
    } 
 
    return (n % divisor == 0), nil 
} 

We're dividing 10 by 0 again but now the output of this function is A number cannot be divided by zero. Error captured, the program finished gracefully.