CODEWITHSUNDEEP
go
dlasalle
dlasalle

Reputation: 1725

How get a pointer to a value in a map in Go

I would like to get a pointer to a map value (which contains structs), so that I can modify a field in the struct, without having to re-assign it.

type Foo struct {
    Bar int64
}

func SomeFunction(arg * Foo) {
    ...
}

What I currently have to do:

if val, ok := myMap[idx]; ok {
  // val is of type `Foo`
  SomeFunction(&val)
  myMap[idx] = val
}

What I'd like to do:

if val, ok := getPointer(myMap, idx); ok {
  // val is of type `* Foo`
  SomeFunction(val)
}

Is there a way to do this Go, or do I need to rely on the compiler being smart enough to perform copy elision here?

Upvotes: 8

Views: 12067

Answers (1)

Eugene Lisitsky
Eugene Lisitsky

Reputation: 12845

For this operation you may use map with pointers. Like:

var myMap map[int]*Foo

if _, val := range myMap {
  // val is of type `* Foo`
  SomeFunction(val)
}

Upvotes: 8

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