a quick overview of Golang for Object oriented programmers

1. GoLang for OO Programmers
Khalid Nowaf COSC 419
Special Topic : Golang and Docker
Computer Science
Okanagan College, 2016

2. Before We Start
 Import The presentation Packages by using this Commands
 go get github.com/Khalid-Nowaf/goExample
 go get github.com/Khalid-Nowaf/animal
 go get github.com/Khalid-Nowaf/embedded
 You should find all the code in this path
 {GOPATH}/src/github.com/Khalid-Nowaf
 The goExample package include the main files for our examples, where animal and embedded
packages just the implementation
 You should run any file in goExample by using this command
 go run {filename}
 E.g. go run class.go

3. Agenda
 Struct Types ”As Class”
 Constructor and Custom Constructor “Factory”
 Private and Public Struct Members
 Embedded types (Composition)
 Shadowing Fields and Methods
 Interfaces

4. Is GoLang OO ?
 Classes
 Encapsulation
 Inheritance
 Interfaces
 Composition
 delegation
 Polymorphism
“ Objects are like people. They’re
living, breathing things that have
knowledge inside them about how to
do things and have memory inside
them so they can remember things.
And rather than interacting with
them at a very low level, you interact
with them at a very high level of
abstraction, like we’re doing right
here. “Steve Jobs

5. Classes
Fields Methods
From Khalid-Nowaf/animal/animal.go

6. Object
In Go there is no such thing called Objects , but there is Types !
How to use ”this” keyword in Go ?

7. Constructor
Go has Built-in Constructor, but limited.
From Khalid-Nowaf/animal/animal.go

8. Custom Constructor
To simulate the Constructor we create a method that return a new
instance . AKA Factory in Design pattern
.
.
.
From Khalid-Nowaf/animal/animal.go

9. Private vs Public Members
There is only one rule
Capital is Public ”exported”
Small is Private “unexported”
From Khalid-Nowaf/animal/animal.go

10. Classes In Action
To follow me make sure you Import my package by using this commands
go get github.com/khalid-nowaf/animal
go get github.com/khalid-nowaf/goExample
You will find the code in this path
{GOPATH}/src/Khalid-Nowaf/animal  Code implementation “package”
{GOPATH}/src/Khalid-Nowaf/goExample  Code Execution “main”

11. Inheritance and Composition
 Embedding akin to multiple inheritance
 embedded field named as “anonymous field”
 Let's call "base" the struct embedded
 And "derived" the struct doing the embedding.
 Base fields and methods are available as if they were declared in the
derived struct.
 But base fields and methods can be "shadowed"
 Shadowing: defining another field or method with the same name
(and signature) of a base field or method

12. Embedding and Shadowing
embedded.go “main”
output
embedded.go “Package”

13. Multiple Embedding
multiEmbedded.go “Package”

14. Multiple Embedding In Action
multiEmbedded.go (main)

15. More In Shadow Methods
Emedded.go “package”
Emedded.go “main”

16. Multiple inheritance and The Diamond Problem
 Golang solves the diamond problem by not allowing
diamonds.
 all embedded class-field-names should not collide
 You must rename fields if there is a name collision
 This rule avoids the diamond problem, by not allowing it

17. Interfaces
 The interface in Golang is designed to complement structs
 Struct: has fields and NON-VIRTUAL methods
 While, Interface has with NO fields, ALL VIRTUAL methods
 you can use an interface to:
 Declare a var or parameter of type interface.
 implement an interface, by declaring all the interface virtual
methods in a concrete class (a struct)
 Inherit (embed) a golang-interface into another golang-
interface

18. Interfaces = Polymorphism In Action
Since the code will not fit the slide ! , lets open
{GOPATH}/src/github.com/Khalid-Nowaf/animal/animal.go

19. To Sum-up …
 A golang struct-method
 It is defined outside of the class(struct) body
 extra section before the method name to define the "receiver" (this)
 Structs vs Interfaces
 Structs: **classes, with fields, ALL NON-VIRTUAL methods
 Interfaces: **classes, with NO fields, ALL VIRTUAL methods
 Interfaces used to impalement Polymorphism
 Shadowing: means defining another field or method with the same name (and
signature) of a base field or method
 GoLang can act as OOP if you wish , but its not by design