Best Way to Return a Value from a Function [closed]

Question

In my example, Method1 uses a variable to store the return values and then assigns the variable to the function. Method2 adds the return values directly to the function.

Questions:

1. What is the pattern of Method2 called?
2. Is one method prefered over the other and why?

---

Function Method1(FirstNumber As Long, LastNumber As Long) As Collection
    Dim Map As New Collection
    Dim n As Long
    
    For n = FirstNumber To LastNumber
         Method1.Add n
    Next
    
    Set Method1 = Map
End Function

Function Method2(FirstNumber As Long, LastNumber As Long) As Collection
    Set Method2 = Collection
    Dim n As Long
    
    For n = FirstNumber To LastNumber
        Method2.Add n
    Next    
End Function

Addendum

Could someone explain the votes to close the question? I have written well over 50 of these types of functions this year alone. Not to mention that as a contributor to SO, I feel like hearing from other developers opinions on the subject will help me improve my answers.

Feel free to down vote and vote to close the question again for me commenting in my post.

Edit 1

There was a typo in my original code. This is how Method1 should have been written.

Function Method1(FirstNumber As Long, LastNumber As Long) As Collection
    Dim Map As New Collection
    Dim n As Long
    
    For n = FirstNumber To LastNumber
         Map.Add n
    Next
    
    Set Method1 = Map
End Function

I restored my original post and added this edit for clarification.

Answer 1

Method 1 is marginally (really barely) less efficient because of the additional variable. However Method 2 sometimes doesn't do what you might want (/expect):

Function Method2(LastNumber As Long) As Collection
    Set Method2 = New Collection
    Dim n As Long
    
    For n = 1 To LastNumber
        Method2.Add n
    Next
    
    'print the first item from the collection for logging
    Debug.Print Method2(1) 'Stack Overflow?!
    
End Function

Or

Function Method2(Optional ByVal LastNumber As Long = 5) As Collection
    Set Method2 = New Collection
    Dim n As Long
    
    For n = 1 To LastNumber
        add_n Method2(), n 'blink and you miss it, not the most obvious error
    Next
End Function

Sub add_n(ByVal coll As Collection, ByVal n As Long)
    coll.Add n
End Sub

It's just a bit higher risk; confusing a variable with a function call. That makes Method 1 better in my book unless you are doing something performance critical or a one-liner (e.g. I would assign directly to the function name if I'm doing low level stuff with pointers and API calls)

I call the return variable result which encourages me not to forget to assign it to the function name at the end

---

Even weirder error:

Function Method2(LastNumber As Long) As Scripting.Dictionary
    Set Method2 = New Dictionary
    Dim n As Long
    
    Method2(1) = "First value" 'Argument not optional error, try work that one out
    For n = 2 To LastNumber
        Method2.Add n, n
    Next
End Function

Answer 2

The usage of the temporary variable instead of the implicit function named variable is to follow Return patterns seen in other languages. This is a case of just because VBA lets you do it, doesn't mean you should.

This argument says that you should only set the return once, at the end of the function. Coding this way makes your code easier to read if the reader expects a return at the bottom of the function.

Let's compare VB.NET to VBA here:

VB.NET:

Function Method1(FirstNumber As Long, LastNumber As Long) As List(Of Long)
    Dim map As New List(Of Integer)
    
    Dim n As Long
    For n = FirstNumber To LastNumber
        map.Add(n)
    Next
    
    Return map
End Function

The VBA code is similar except we swap the Return for a Set

Function Method1(FirstNumber As Long, LastNumber As Long) As Collection
    Dim map As Collection
    Set map = New Collection
    
    Dim n As Long
    For n = FirstNumber To LastNumber
        map.Add n
    Next
    
    Set Method1 = map  ' Return
End Function

This is valuable if you ever want to port your VBA code to a VB.NET project later.