Structs
caution
Structs are value types.
A struct is a collection of fields.
package main
import "fmt"
type Vertex struct {
X int
Y int
}
func main() {
fmt.Println(Vertex{1, 2})
}
// {1 2}
Struct Fields
Struct fields are accessed using a dot.
package main
import "fmt"
type Vertex struct {
X int
Y int
}
func main() {
v := Vertex{1, 2}
v.X = 4
fmt.Println(v.X)
}
// 4
Pointers to structs
Struct fields can be accessed through a struct pointer.
{% hint style="success" %}
To access the field X of a struct when we have the struct pointer p we could write (*p).X. However, that notation is cumbersome, so the language permits us instead to write just p.X, without the explicit dereference.
{% endhint %}
package main
import "fmt"
type Vertex struct {
X int
Y int
}
func main() {
v := Vertex{1, 2}
p := &v
p.X = 1e9
fmt.Println(v)
}
Struct Literals
A struct literal denotes a newly allocated struct value by listing the values of its fields.
You can list just a subset of fields by using the Name: syntax. (And the order of named fields is irrelevant.)
The special prefix & returns a pointer to the struct value.
package main
import "fmt"
type Vertex struct {
X, Y int
}
var (
v1 = Vertex{1, 2} // has type Vertex
v2 = Vertex{X: 1} // Y:0 is implicit
v3 = Vertex{} // X:0 and Y:0
p = &Vertex{1, 2} // has type *Vertex
)
func main() {
fmt.Println(v1, p, v2, v3)
}
// {1 2} &{1 2} {1 0} {0 0}
Tags
package main
import (
"fmt"
)
type Student struct {
Name string `label:"full name"`
}
func main() {
s := Student{"MyFullName"}
fmt.Println(s)
}
// {MyFullName}