Pulling data objects from a collection of various data types stored

[kevinwolfe]

Hello all,

I have a class which inherits 'Collection' and I use this class to
store different data types. I'd like to have a method inside the class
that does the following:

For Each obj As Object In new_linked_collection
Me.DoSomething(obj)
Next

where DoSomething is overloaded for each of the different data types
I'm storing in the collection. The problem is, as I've defined obj as
an Object, visual basic craps a brick unless I recast obj to a
particlar type, such as

For Each obj As Object In new_linked_collection
If (obj.GetType.ToString.Equals("MyProgram.MyDataType1"))
Then
Dim castedObj As MyDataType1 = obj
Me.DoSomething(castedObj)
Else
Dim castedObj As MyDataType2 = obj
Me.DoSomething(castedObj)
End If
Next

There has to be a more elegate way of doing this (expecially as I have
more than 2 different data types stored in the collection). Any
suggestions?

Thanks a bunch,

Kevin

 

[Patrick Steele]

Hello all,

I have a class which inherits 'Collection' and I use this class to
store different data types. I'd like to have a method inside the class
that does the following:

For Each obj As Object In new_linked_collection
Me.DoSomething(obj)
Next

where DoSomething is overloaded for each of the different data types
I'm storing in the collection. The problem is, as I've defined obj as
an Object, visual basic craps a brick unless I recast obj to a
particlar type, such as

For Each obj As Object In new_linked_collection
If (obj.GetType.ToString.Equals("MyProgram.MyDataType1"))
Then
Dim castedObj As MyDataType1 = obj
Me.DoSomething(castedObj)
Else
Dim castedObj As MyDataType2 = obj
Me.DoSomething(castedObj)
End If
Next

There has to be a more elegate way of doing this (expecially as I have
more than 2 different data types stored in the collection). Any
suggestions?

One idea is to use interfaces. Create an interface with a method called
DoSomething:

Public Interface IWorker
Sub DoSomething()
End Interface

Have each of the "types" of objects you're storing in the collection
implement the interface. Then just:

for each obj as IWork in new_linked_collection
obj.DoSomething()
next

Another idea is to change the type of parameter DoSomething receives to
be an object and then use TypeOf to see what type is passed in:

public sub DoSomething(o as object)
if typeof(o) is MyDataType1
dim dt1 As MyDataType1 = DirectCast(o, MyDataType1)
' use dt1
end if

if typeof(o) is MyDataType2
dim dt2 As MyDataType2 = DirectCast(o, MyDataType2)
' use dt2
end if
end if