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    <p>I'm not sure if this is what you're looking for, but I'll give it a shot. If Car class contains one Speedometer class, Car contains Windspeed and Acceleration properties, Speedometer contains a Mass property, and speed is defined as Windspeed times Acceleration divided by Mass, then here's how I would set it up.</p> <p>In class CCar</p> <pre><code>Private mlCarID As Long Private mdWindSpeed As Double Private mdAcceleration As Double Private mclsSpeedometer As CSpeedometer 'Getters and setters Public Property Get CarID() As Long: CarID = mlCarID: End Property Public Property Let CarID(ByVal lCarID As Long): mlCarID = lCarID: End Property Public Property Get Acceleration() As Double: Acceleration = mdAcceleration: End Property Public Property Let Acceleration(ByVal dAcceleration As Double): mdAcceleration = dAcceleration: End Property Public Property Get WindSpeed() As Double: WindSpeed = mdWindSpeed: End Property Public Property Let WindSpeed(ByVal dWindSpeed As Double): mdWindSpeed = dWindSpeed: End Property 'read only property to the speedometer class Public Property Get Speedometer() As CSpeedometer Set Speedometer = mclsSpeedometer End Property 'create the child and set the parent property Private Sub Class_Initialize() Set mclsSpeedometer = New CSpeedometer Set mclsSpeedometer.Parent = Me End Sub Private Sub Class_Terminate() Set mclsSpeedometer.Parent = Nothing Set mclsSpeedometer = Nothing End Sub 'pass through property Public Property Get Speed() As Double Speed = Me.Speedometer.Speed End Property </code></pre> <p>In class CSpeedometer</p> <pre><code>Private mdMass As Double Private mclsParent As CCar Public Property Get Mass() As Double: Mass = mdMass: End Property Public Property Let Mass(ByVal dMass As Double): mdMass = dMass: End Property Public Property Get Parent() As CCar Set Parent = mclsParent End Property Public Property Set Parent(clsCar As CCar) Set mclsParent = clsCar End Property Public Property Get Speed() As Double 'references to parent properties Speed = Me.Parent.WindSpeed * Me.Parent.Acceleration / Me.Mass End Property </code></pre> <p>In a standard module</p> <pre><code>Sub GetSpeed() Dim clsCar As CCar Set clsCar = New CCar clsCar.CarID = 1 clsCar.WindSpeed = 10 clsCar.Acceleration = 5 clsCar.Speedometer.Mass = 100 Debug.Print clsCar.Speed End Sub </code></pre> <p>You have to make sure you destroy your parent/child relationship properly or you'll get a memory leak. I use CopyMemory to set up parent properties to avoid that particular problem. It's described here <a href="http://www.dailydoseofexcel.com/archives/2007/12/28/terminating-dependent-classes/#comment-29661" rel="nofollow">http://www.dailydoseofexcel.com/archives/2007/12/28/terminating-dependent-classes/#comment-29661</a></p>
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    1. POVBA Referring to a container object--syntax and object-oriented methodology
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    1. COThanks much for the extensive effort, Dick. What I'm wondering if it could be done differently is this: Public Property Get Parent() As CCar. The problem it seems to me, is that Parent could be CCar, CBus, CTruck... . I was hoping to get a reference to any of various (but similar) possible parents in one swoop. Instead of having multiple properties (by name, or by overloading with types). Now it occurs to me that in a more powerful language, I would just have all my vehicles inherit from Vehicle, and use that single type for Parent. I could also use Variant/Object, but was hoping to avoid.
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    2. COAnd I guess the "MyContainer" concept (as a keyword, like "Me") may be flawed, b/c it tries to assume that there is a container, which may be difficult or undesirable.
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    3. COI'm voting this up because I think it's a good answer to actual question asked - how to give a contained object access to the state of its container. However, as I explain in my own answer, I think the design behind that question is the wrong design in this case.
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