Initialising multiple structs in go

Question

I need to initialise multiple struct variables

Let's say the struct is

type Foo struct {
  a int
  b *Foo
}

And let's say I want to initialise 5 of those. Is there a cleaner way of doing it than below fragment multiple times?

s0 := &Foo{}
s1 := &Foo{}
s2 := &Foo{}

something like

var a, b, c, d int

Thanks for help! : )

score 7 · Accepted Answer · 2014-04-04 13:22:16Z

7

You can put them in one statement if you want:

s0, s1, s2 := new(Foo), new(Foo), new(Foo)

You can also do this:

var s0, s1, s2 Foo

And then use &s0, &s1 and &s2 subsequently instead of s0, s1 and s2.

edited Apr 4, 2014 at 13:22

answered Mar 30, 2014 at 12:22

user1804599

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Comments

Dustin · Accepted Answer · 2014-03-30 07:04:55Z

1

Do you require pointers? If not, the you have exactly the answer in your question. Just replace int with your type in your var statement.

answered Mar 30, 2014 at 7:04

Dustin

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1 Comment

Paul Hankin Over a year ago

Sorry Dustin, you're right. The wording of your answer confused me, and I've removed the comment.

Paul Hankin · Accepted Answer · 2014-03-30 07:08:05Z

1

You can use a loop and a slice to allocate 5 foos.

 foos := make([]*Foo, 5)
 for i := range foos {
     foos[i] = &Foo{}
 }

An alternative would be to use an array:

 foos := [5]Foo{}

and use &foos[0], &foos[1], ... as your pointers.

answered Mar 30, 2014 at 7:08

Paul Hankin

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Comments

Vector · Accepted Answer · 2014-04-03 02:55:19Z

0

Preferred way would be to wrap this in a factory function (which you should do anyhow):

func NewFoos(count int) []foo {
    return make([]foo, count, count)
}

This is clean, concise and soft: Allows you to easily initialize as many or as few as you need.

edited Apr 3, 2014 at 2:55

answered Mar 30, 2014 at 21:32

Vector

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2 Comments

user1804599 Over a year ago

There is no need for the loop. Just return make([]foo, count) is sufficient. make already constructs the elements of the slice to their zero values.

Vector Over a year ago

I thought about your point after I posted this - didn't get a chance to test it. At the time I thought that maybe makewould just allocate the memory but not the foo instance. I edited, taking your word for it.:)

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