In Golang, structs are simple containers for data.
- can have fields
- no methods attached to them
- methods defined separately and associated with a
structtype.
- methods defined separately and associated with a
The following show a simple Book class equivalents in Ruby and GoLang.
class Book
attr_reader(:title, :author)
def initalize(title, author)
@title = title
@author = authoer
end
end
# usage
book = Book.new('Title', 'Jon Snow')
// Equivalent to `class Book` in ruby
type Book struct {
Title string,
Author string
}
Instantiating GoLang type
Composite Literal
Composite Literal is syntax to create an initialise composite types in one step. We can instantiate the following types:
- structs
- arrays
- slices
- maps
Here we are assigning a new Book instance to the variable book
// Composite Literal
book := Book{
Title: "Title",
Author: "Author"
}
Using new keyword
The longer form is to use the new keyword. This would be similar to the way we would instantiate a class in Ruby with book = Book.new(..)
We would assign the attributes of the book (i.e. Title and Author) using = sign.
// Using the `new` keyword
book := new(Book)
book.Title = "Book Title"
book.Author = "John Snow"
Without Short Variable Declaration (:=)
Notice that we used the symbol := in the first example?
It's syntactic sugar for the following verbose way of declaring a variable and assigning it a value.
// Without Short Virable Declaration
// Example 1
var book Book // Declare variable `book` of type `Book`
book.Title = "Book Title" // Assign the value to book variable
book.Author = "John Snow"
// Example 2
var count int
count = 20
Factory Function
We could also use the factory pattern to make it easier when initialising the struct when we need to:
- add additional logic
- add default values
Assuming we would want to make each first character of the book's title and author tokens to be capitalised.
// Factory Function
func NewBook(title string, author string) Book {
return Book{
Title: titlelise(title), // default logic to "titlelise"
Author: titlelist(author)
}
}
func titlelise(str string) {
caser := cases.Title(lanaguage.English)
return caser.String(str)
}
Attaching a function to a struct
In Ruby, we would simply define a function within the class. Here, we are defining a function called to_string() to print the book title name author.
class Book
attr_reader(:title, :author)
def initalize(title, author)
@title = title
@author = authoer
end
# new function we added
def to_string()
put "#{title} by #{string}"
end
end
In GoLang, we would "attach" the function by passing in the stuct to the function.
// Equivalent to `class Book` in ruby
type Book struct {
Title string,
Author string
}
// Attaching the function to the `struct`
func (book Book) ToString() string {
return fmt.Sprintf("%s by %s", book.Title, book.Author)
}
// Usage
book := Book{
Title: "Title",
Author: "Author"
}
book.ToString()
// => Title by Author
Explanation of:
func (book Book) ToString() string
| Token | Description |
|---|---|
func |
function keyword |
(book Book) |
Attaching the function to the type Book struct- book: variable to access the struct within the function- Book: type of the struct
|
ToString() |
name of the function |
string |
return type of the function |
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