Structs

A struct is a collection of fields. Struct fields are accessed using a dot.

Example

package main

import "fmt"

type Vertex struct {
    X int
    Y int
}

func main() {
    fmt.Println(Vertex{1, 2})
    
    v := Vertex{1, 2}
    v.X = 4
    fmt.Println(v.X)
}

{1 2}
4

Pointers to Structs

Struct fields can also be accessed using a struct pointer.

package main

import "fmt"

type Vertex struct {
    X int
    Y int
}

func main() {
    v := Vertex{1, 2}
    p := &v           // struct pointer p
    p.X = 1e9
    // (*p).X = 9     // output would be {9 2}
    fmt.Println(v)
}

{1000000000 2}

We could write (*p).X to access the field X of the Vertex struct. However, this is a cumbersome notation. So, Go allows us to use p.X without this explicit derefence.

Struct Literals

A struct literal denotes a newly allocated struct value by listing the values of its fields. The predix & returns a pointer to the struct value.

package main

import "fmt"

type Vertex struct {
    X, Y int
}

var (
    v1 = Vertex{1, 2}
    v2 = Vertex{X: 1}    // using Name: syntax; Y: 0 is implicit
    v3 = Vertex{}        // X:0 and Y:0
    p = &Vertex{1, 2}    // has type *Vertex
)

func main() {
    fmt.Println(v1, v2, v3, p)
}

{1 2} {1 0} {0 0} &{1 2}