Single instance of a class to be available to all instances or all other classes

Posted on 2012-03-21
Last Modified: 2012-03-22
I am developing some class modules to run a specialised simulation and need a simulation clock to be available to the objects in the simulation.

I have a clock class that returns the time as a property, see below.

How can I make the one clock available to all other objects?  

Private piTime As Integer

Private Sub Class_Initialize()

    piTime = 0

End Sub

Public Property Get Time() As Integer

    Time = piTime

End Property

Public Sub Tick()

    piTime = piTime + 1

End Sub

Public Sub Clear()

    piTime = 0

End Sub

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Question by:sjgrey
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LVL 85

Expert Comment

by:Rory Archibald
ID: 37751603
You would need all your other classes to have a property (say 'Clock') to which you assign the clock instance when you create each instance of the other classes.

Author Comment

ID: 37751912
I have a Class_Initialize subroutine within the modules that use the clock but I don't see, to be able to pass it parameters.  Will I have to use a separate "Let" procedure with a separate line such as

Object.Clock = SimClock

followed by, within the object

Public Property Let Clock(SimClock as clsSimClock)
Set Clock = SimClock
End Property

to establish the connection to the clock or is there an easier way to include it when instantiating the modules that need the clock?
LVL 85

Accepted Solution

Rory Archibald earned 500 total points
ID: 37751990
VBA doesn't give you a constructor you can use, so you'll need the property though it needs to be a Property Set rather than Let as you are passing an object.

Author Closing Comment

ID: 37755664
That worked thanks.  Code in the class required to use the clock as follows in case it is of interest to anyone else.

Private pClock As clsSimClock

Public Property Set SimClock(Clock As clsSimClock)

    Set pClock = Clock

End Property

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And in the code that sets up the class instances

    Dim SimClock As clsSimClock
            Set Unit.SimClock = SimClock

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