Helper func for OptNil types

[adrianlungu]

Hello,

While using ogen, I've often run into code where we check if an OptNil type IsSet and !IsNull as the end field is a pointer, so I thought, why not have a different helper Get function that returns &Value or nil ?

i.e. if we have

{
   field: "value"
}
or 
{
   field: ""
}
or 
{
   field: null
}
or
{
}

If value of field is null or missing altogether, it would return nil, otherwise it would return a pointer to "" or "value".

[tdakkota]

Get method returns ("", false) in case if value is absent or is null.

You can use generics to write a simple helper function to get a pointer:

func AsPtr[
	T any,
	OptT interface {
		Get() (T, bool)
	},
](o OptT) *T {
	v, ok := o.Get()
	if !ok {
		return nil
	}
	return &v
}

Probably we should add an AsPtr method to optionals.

[adrianlungu]

Thanks!

That's what I ended up doing; if I have some time, might make a PR to add them over here as well.