Return object from class function

Question

I have a namespace with a class inside it with another class inside that, i.e.

namespace MySpace
    public class MainClass
        public class SubClass
            public x as integer
            public z as integer
        end class

        public function Foo ()
            dim y as SubClass
            y.x = 5
            return
        end function
    end class
end namespace

except the line y.x = 5 gets underlined with the tip "Variable y is used before it has been assigned a value. A null exception could result at runtime"

Basically I want to be able to have the multiple items that Foo assigns then available to whatever other code is using the MainClass class. What is the safest way to do this? If I was doing this in C I would have used a struct but apparently they are less efficient in VB?

NoAlias · Accepted Answer · 2013-07-03 18:10:03Z

2

You could make x and z shared:

    Public Class SubClass
        Public Shared x As Integer
        Public Shared z As Integer
    End Class

Or you can instantiate a class-level variable:

Public Class MainClass

    Private m_objSubClass As New SubClass2

and call like so:

    Public Function Foo()
        'Shared
        SubClass.x = 5
        'Instantiated Class-Level variable
        m_objSubClass.x = 5
    End Function

If the Subclass needs to be accessed by other classes then expose the instantiated version through a Property instead of just a private variable (or return the instantiated version in your function).

Return m_objSubClass

Finally, if your values do not need to persist, you could simply instantiate a Subclass2 in the function:

Dim objSubClass2 As New SubClass2
objSubClass2.X = 5
Return objSubClass2

edited Jul 3, 2013 at 18:10

answered Jul 3, 2013 at 17:58

NoAlias

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2 Comments

Toby Over a year ago

Thanks, How would I make it so that the properties of subclass are available publicly (outside of mainClass) while the members are available only to mainClass but not outside of it?

NoAlias Over a year ago

Have a Public Property on your Main Class that returns m_objSubClass. That way it would be "objInstanceOfMainClass.PropertyNameOfSubClass.X = 5"

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