Easy way to assign int pointer values?

Question

Given a struct that looks like

type foo struct {
 i *int
}

if I want to set i to 1, I must

throwAway := 1
instance := foo { i: &throwAway }

Is there any way to do this in a single line without having to give my new i value it's own name (in this case throwaway)?

I recommend to check [this extensive answer](https://stackoverflow.com/questions/30716354/how-do-i-do-a-literal-int64-in-go/30716481#answer-30716481) to a very similar question. — Arnau, Jan 22 '21 at 14:25

score 10 · Accepted Answer · answered Apr 08 '15 at 16:57

10

As pointed in the mailing list, you can just do this:

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

and then

instance := foo { i: intPtr(1) }

if you have to do it often. intPtr gets inlined (see go build -gcflags '-m' output), so it should have next to no performance penalty.

answered Apr 08 '15 at 16:57

Ainar-G

You can also do `instance := foo{ i: new(int) }; foo.i = 1;` if you don't want to write a separate function. – fuz Apr 08 '15 at 17:38
That's not right @FUZxxl, you can't assign `1` as a type `int` to `*int`. You end up back in the same situation as the OP. – Pero P. Apr 08 '15 at 18:17
2

Sorry, try `instance := foo{i : new(int) }; *foo.i = 1;` – fuz Apr 08 '15 at 18:31
@fuz I get this: `type ‘foo’ has no method ‘i’` – exebook Mar 03 '17 at 18:15
@exebook Please ask a new question for that if you can't solve it yourself. – fuz Mar 03 '17 at 21:09

score 5 · Answer 2 · answered Apr 08 '15 at 16:51

5

No this is not possible to do in one line.

answered Apr 08 '15 at 16:51

Volker

2

Gross. Any thoughts as to why not? Is it just too difficult to implement to remove an occasionally noisy line? – MushinNoShin Apr 08 '15 at 16:54
6

@MushinNoShin: a pointer is the address of some thing, so you need that *thing*. – maerics Apr 08 '15 at 16:57
1

@maerics: that was already understood, this was asking if there's any convenient ways to automatically do the memory allocation in the background and keep the unnecessary noise out of my code. See the accepted answer. – MushinNoShin Apr 08 '15 at 17:26
1

Pointers to ints are not that common and pointers to literal ints are very uncommon, so why bother with syntactical sugar? – Volker Apr 08 '15 at 20:17
@Volker you should take a look at `aws-sdk-golang`, they've got pointers to literal ints for days. – Civilian May 04 '15 at 22:19

2 Answers2