[Go](EN) Go language struct and method basic usage
Post about basic usage of struct and method in Go language
Environment and Prerequisite
- Go(1.15.8)
- Experience with other programming languages
Struct and Method
Struct in Go
- Go language supports its own way of OOP. There is no class in Go. Also no class so no inheritance.
- So it use struct and method.
- Briefly write about struct and method in below.
Struct Example
- There are four ways like below example.
- We can use keyword
newor we can make constructor function.
package main
import (
"fmt"
)
// define struct
type Rectangle struct {
width int
height int
}
// define constructor
func NewRectangle(width int, height int) *Rectangle{
return &Rectangle{width, height}
}
func main() {
// create instances
var rec1 = Rectangle{}
rec1.width = 2
rec1.height = 3
rec2 := Rectangle{4, 5}
var rec3 = new(Rectangle)
rec3.width = 6
rec3.height = 7
var rec4 = NewRectangle(8, 9)
// check instances
fmt.Println(rec1.width, rec1.height)
fmt.Println(rec2.width, rec2.height)
fmt.Println(rec3.width, rec3.height)
fmt.Println(rec4.width, rec4.height)
}
2 3
4 5
6 7
8 9
Method Example
- By using receiver, we can define method for specific class.
- There are value receiver and pointer receiver.
- In below example,
(r Rectangle)and(r *Rectangle)are receivers.
package main
import (
"fmt"
)
// define struct
type Rectangle struct {
width int
height int
}
// define constructor
func NewRectangle(width int, height int) *Rectangle{
return &Rectangle{width, height}
}
// define methods
func (r Rectangle) area() int{
return r.width * r.height
}
// pointer receiver
func (r *Rectangle) setWidth(width int){
r.width = width
}
// value receiver
func (r Rectangle) setHeight(height int){
r.height = height
}
func main() {
// create instances
var rec = NewRectangle(8, 9)
// check instances
fmt.Println(rec.width, rec.height)
fmt.Println()
// check methods
fmt.Println(rec.area())
fmt.Println()
rec.setWidth(10)
// rec.height would not be changed because its method's receiver is value receiver
rec.setHeight(10)
fmt.Println(rec.width, rec.height)
}
8 9
72
10 9