Fix "cannot take address of <value>" in Go

Jacob Hummer - Apr 21 - - Dev Community

This is a summary of my Googling for future me or anyone else.

fmt.Println(&"Hello")
fmt.Println(&true)
fmt.Println(&15)
fmt.Println(&fmt.Sprint(123))
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./prog.go:8:15: invalid operation: cannot take address of "Hello" (untyped string constant)
./prog.go:9:15: invalid operation: cannot take address of true (untyped bool constant)
./prog.go:10:15: invalid operation: cannot take address of 15 (untyped int constant)
./prog.go:11:15: invalid operation: cannot take address of fmt.Sprint(123) (value of type string)
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You currently can't get the address of literals or function return values in Go. You can, however, get the address of function parameters which means you can create a helper ptr() function to turn any value into a pointer. 😉

func ptr[T any](value T) *T {
  return &value
}
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func ptr[T any](value T) *T {
  return &value
}
func main() {
  fmt.Println(ptr("Hello"))
  fmt.Println(ptr(true))
  fmt.Println(ptr(15))
  fmt.Println(ptr(fmt.Sprint(123)))
}
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Of course, you could always stuff these values into a variable and &theVariable. 🙄 But who wants to clutter their code with extra one-time intermediary variables?

a := "Hello"
fmt.Println(&a)
b := true
fmt.Println(&b)
c := 15
fmt.Println(&c)
d := fmt.Sprint(123)
fmt.Println(&d)
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Further reading 📚

Judging from the past 1.5 years, I appear to be writing this function about once every second month, when I need it in a new package. The need especially arise with pointers to strings in unit test files, I've noticed.

Admittedly, I work a lot with code generated from API specifications. That code tend to use *string a lot, since it can't be certain that nil and empty string are equivalent (and rightly so, they aren't).

It's not very annoying, but does feel a bit like I'm littering my packages with this function, so not having to write it would be welcome. I do realise I can put it in a package I import, but that also seems overkill for a one-liner.

@perj in golang/go#45624 (comment)

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