How to get the pointer of return value from function call?

Question

I just need a pointer to time.Time, so the code below seems invalid:

./c.go:5: cannot take the address of time.Now()

I just wond

Answer 1

You can't directly take the address of a function call (or more precisely the return value(s) of the function) as described by hobbs.

There is another way but it is ugly:

p := &[]time.Time{time.Now()}[0]
fmt.Printf("%T %p\n%v", p, p, *p)

Output (Go Playground):

*time.Time 0x10438180
2009-11-10 23:00:00 +0000 UTC

What happens here is a struct is created with a literal, containing one element (the return value of time.Now()), the slice is indexed (0^th element) and the address of the 0^th element is taken.

So rather just use a local variable:

t := time.Now()
p := &t

Or a helper function:

func ptr(t time.Time) *time.Time {
    return &t
}

p := ptr(time.Now())

Which can also be a one-liner anonymous function:

p := func() *time.Time { t := time.Now(); return &t }()

Or as an alternative:

p := func(t time.Time) *time.Time { return &t }(time.Now())

For even more alternatives, see:

How do I do a literal *int64 in Go?

Also see related question: How can I store reference to the result of an operation in Go?