How to initialise a pointer member in a struct type inline?

Question

With a type:

type A struct {
   B int, C *int
}

How do I initialise a pointer member to a non-zero value inline, without creating temporaries?

a := A{
    B: 42,
    C: ?,
}

Answer 1

For the specific example you've given you are limited in what you can do without introducing additional statements.

If you want C to point at an initialised integer variable, you will need an additional statement to define that variable since you can't take the address of an integer literal (ie &42 would be an error).

If you just want to initialise C as a pointer to a new zero value, you are in luck though and can set it to new(int) .

If you were instead dealing with a different type that had an initialiser syntax, you would also been in luck. For example, if C was a pointer to a structure, you could initialise it to &TheStruct{...} .

If none of these are appropriate, and you are really only after code clarity for initialising *int variables, a helper function might fit your requirements. For example:

func makeIntPointer(v int) *int {
    return &v
}

Answer 2

package main

import "fmt"

type A struct {
    B int 
    C *int
}

func newint(i int) *int{
    return &i
}

func main() {
    c := newint(5)
    a := &A{
            B: 42,
            C: c,
         }

    fmt.Printf(" %v" , *a.C)
    fmt.Printf(" %#v" , a.C)
}

http://play.golang.org/p/s0HIMHoMRo