Setting pointers using reflect.

[Paul Borman]

I am trying to build up a structure using reflect.  Most of it is fine, but not when it comes to elements that have pointers.

In my code I would like to have:

    switch v.Kind() {

    case reflect.Ptr:

        val := reflect.New(v.Type().Elem())

        v.Set(val)

    ...

    }

which yields

    panic: reflect.Value·Set using unaddressable value

v was obtained as follows:

    s := &struct{P *int}

    v := reflect.ValueOf(s).Elem().Field(0)

so initially v is a nil pointer.  What is the correct way, using reflect, to create an new value to assign to a pointer?

Thanks,

    -Paul

[Kyle Lemons]

The code you have seems to work on the playground:

http://golang.org/doc/play/#package%20main%0A%0Aimport%20%22fmt%22%0Aimport%20%22reflect%22%0A%0Afunc%20main()%20%7B%0A%20%20%20%20type%20st%20struct%7BP%20*int%7D%0A%20%20%20%20s%20%3A%3D%20%26st%7B%7D%0A%20%20%20%20v%20%3A%3D%20reflect.ValueOf(s).Elem().Field(0)%0A%20%20%20%20switch%20v.Kind()%20%7B%0A%20%20%20%20case%20reflect.Ptr%3A%0A%20%20%20%20%20%20%20%20val%20%3A%3D%20reflect.New(v.Type().Elem())%0A%20%20%20%20%20%20%20%20v.Set(val)%0A%20%20%20%20%7D%0A%0A%20%20%20%20fmt.Printf(%22%25v%22%2C%20*s.P)%0A%7D%0A

~K

[Paul Borman]

Well look at that.  I had simplified the code in my email from a larger test case.  Shame on me for not building the full small test case.  It appears my actual bug was not the Set but when I was trying to fill the contents of val that was being set to v.

Thanks Kyle,

    -Paul