vba - Optimal way of altering multiple values with a function -

functions in vba @ least can ever return 1 thing. thing contain multiple values, it's still 1 package.

i create sub/function has effect on values of more 1 variable. far know, these 3 ways of doing that:

1. declare variables outside caller sub

private val1 long, val2 long sub caller()     val1 = 1     val2 = 2     valuechanger     debug.print val1 + val2         'prints 5 end sub  sub valuechanger()                  'no need pass values, pass both byval     val1 = val1 + 1     val2 = val2 + 1 end sub 

2. pass byref

sub caller()     dim val1 long, val2 long     val1 = 1     val2 = 2     valuechanger val1, val2     debug.print val1 + val2                      'prints 5 end sub  sub valuechanger(byref value1 long, byref value2 long)     value1 = value1 + 1     value2 = value2 + 1 end sub 

3. return both in single "packet"

sub caller()     dim val1 long, val2 long, results() long     val1 = 1     val2 = 2     results = valuechanger(val1, val2)     debug.print results(1) + results(2)          'prints 5 end sub  function valuechanger(byval value1 long, byval value2 long) long() 'return array, equally return collection or string     dim resultvals(1 2) long     resultvals(1) = value1 + 1     resultvals(2) = value2 + 1     valuechanger = resultvals end function 

---

i can see option 3 self-contained, option 1 least. option 3 memory-taxing , requires result split messily.

personally choose option 2 middle ground, think long aware of risks of byref as typing routine, once that's finished can forget variables won't visible anywhere else in code - unlike in option 1.

but have missed something? , of these approaches standard practice should follow?

your third method conceptually simplest, , possibly easier debug (and less need debugging in first place). can simplify mechanics:

1) use variant pass arrays , functions

2) use array() package information return

3) write sub sort of inverse array(), 1 can unpack array list of provided variables (which implicitly uses vba's default byref semantics:

sub unpack(a variant, paramarray vars() variant)     'a 0-based array of same length vars     'the elements of assigned variables in vars     dim long     = 0 ubound(vars)         vars(i) = a(i)     next end sub 

then valuechanger() be:

function valuechanger(byval value1 long, byval value2 long) variant     valuechanger = array(value1 + 1, value2 + 1) end function 

used like:

sub caller()     dim val1 long, val2 long, results variant     val1 = 1     val2 = 2     results = valuechanger(val1, val2)     unpack results, val1, val2     debug.print val1 + val2          'prints 5 end sub 

or just:

sub caller()     dim val1 long, val2 long     val1 = 1     val2 = 2     unpack valuechanger(val1, val2), val1, val2     debug.print val1 + val2          'prints 5 end sub 

alternatively, can implement method 3 expanding mean "packet". typically makes sense return multiple values function when values in sense go together. suggests natural wrap values in type or class:

'at top of module: type pair     val1 long     val2 long end type 

then:

function valuechanger(p pair) pair 'can't pass user-defined type byval     dim q pair     q.val1 = p.val1 + 1     q.val2 = p.val2 + 1     valuechanger = q end function 

used like:

sub caller()     dim p pair     p.val1 = 1     p.val2 = 2     p = valuechanger(p)     debug.print p.val1 + p.val2          'prints 5 end sub