[2005] Class - Efficiency - Which is better practise

[SammyWaslow]

Rather new to the OOP approach, I got some questions concerning efficiency.
In my class I have some private functions. Some properties return values based upon these functions.

Would it be best if I set a variable in my class and Initialize it in the constructor, then return this variable, like so:

Public Class MyMovie
    Private strMovie As String
    Private strName As String
    Private strYear As String
 
    'Constructor
    Public Sub New(ByVal strFullMovieName As String)
        strMovie = strFullMovieName
        strName = DoABunchOfStuff() 'This is a private function in my class
    End Sub
 
    Public ReadOnly Property Name() As String
        Get
            Return strName
        End Get
    End Property
 
(...)

Or by calling the function directly from the property, like so:

Public Class MyMovie
    Private strMovie As String
    Private strName As String
    Private strYear As String
 
    'Constructor
    Public Sub New(ByVal strFullMovieName As String)
        strMovie = strFullMovieName
    End Sub
 
    Public ReadOnly Property Name() As String
        Get
            Return DoABunchOfStuff()
        End Get
    End Property
 
(...)

I reckon that in the latter example each time I 'm getting the value of that property, the private function has to be executed where as in the first example this only happen when creating an instance my class. The first would be more efficient, better. Am I right or ?

[Shaggy Hiker]

The first way would definitely be more efficient as long as you need to get that property more than once. If you only need it once, then the second route may be slightly more efficient.

[SammyWaslow]

The first way would definitely be more efficient as long as you need to get that property more than once. If you only need it once, then the second route may be slightly more efficient.

Think I'll go with the first option.
Could you elaborate a bit on why the second might be a bit more efficient when only needed once? As in Perfomance wise or otherwise?

[jmcilhinney]

If DoABunchOfStuff is a time-consuming operation then it may be preferable to defer its execution until it's needed, particularly if the strName variable and Name property are not needed until the user actually accesses the property. That way your object will be created more quickly and DoABunchOfStuff will never be executed unless it is required. It is possible to defer creation of some member objects but still only execute the code that creates them once like this:

Public Class MyMovie
 
    Private strName As String
 
    Public ReadOnly Property Name() As String
        Get
            If Me.strName Is Nothing Then
                Me.strName = Me.DoABunchOfStuff()
            End If
 
            Return Me.strName
        End Get
    End Property
 
End Class

Note that it is only worth doing this if creating the strName variable is a time-consuming operation and it may not be needed if it is never accessed.

[SammyWaslow]

If DoABunchOfStuff is a time-consuming operation then it may be preferable to defer its execution until it's needed, particularly if the strName variable and Name property are not needed until the user actually accesses the property. That way your object will be created more quickly and DoABunchOfStuff will never be executed unless it is required. It is possible to defer creation of some member objects but still only execute the code that creates them once like this:

Public Class MyMovie
 
    Private strName As String
 
    Public ReadOnly Property Name() As String
        Get
            If Me.strName Is Nothing Then
                Me.strName = Me.DoABunchOfStuff()
            End If
 
            Return Me.strName
        End Get
    End Property
 
End Class

Note that it is only worth doing this if creating the strName variable is a time-consuming operation and it may not be needed if it is never accessed.

Thanks, The private fuction indeed does quite some processing so I want to keep from executing it too much. your solution does seem the way to go.
Thanks!