I understood them to be modules, such as my little one:
Public Module Config
Public Property ImportSettings As ImportConfig
Sub New()
ImportSettings = ImportConfig.Read()
End Sub
End Module
Yet, I cannot access ImportSettings. I'm told it's not declared, and its value is 'Nothing'.
Static(C#)/Shared(VB) method/property in a class:
Public Class Config
Public Shared ReadOnly Property ImportSettings As ImportConfig
Get
Return ImportConfig.Read()
End Get
End Property
End Class
Usage:
Dim configs = Config.ImportSettings
Since it is Static/Shared we do not need to initialize the Config class.
Related
What am I misunderstanding about Private Properties in VBA classes? As a novice, I expected Private Properties to be accessible to other methods within the same class (module), but instead I get "Method or data member not found" when trying to compile.
Breaks as Private Property Let lngMarketID
Here's what I have in my standard module:
Option Explicit
Public Model As classModel
Set Model = New classModel
Model.Setup
with this class module named classModel:
Option Explicit
Private plngMarketID As Long
'plngMarketID Properties
Public Property Get lngMarketID() As Long
lngMarketID = plngMarketID
End Property
Private Property Let lngMarketID(ByVal lngMarketID As Long)
plngMarketID = lngMarketID
End Property
Public Sub Setup()
SetuplngMarketID
End Sub
Private Sub SetuplngMarketID()
Model.lngMarketID = CLng(DefaultLogicOptions.textboxMarketID.Value)
End Sub
Works as Public Property Let lngMarketID
The "Method or data member not found" highlights the .lngMarketID of the line in SetuplngMarketID. This compiles fine when I change Private Property Let lngMarketID to Public Property Let lngMarketID.
It's the "Model" in that line. Model is a global variable pointing to some specific instance of your class. From that object, only the public things are visible.
You want to refer to that from "inside" an arbitrary instance of your class, so just drop the Model prefix:
Private Sub SetuplngMarketID()
lngMarketID = CLng(DefaultLogicOptions.textboxMarketID.Value)
End Sub
You are calling "Model.lngMarketId", Model is the name of your variable of classModel object that isn't visible in the object it self.
you have to use "lngMarketId = Clng(something)"
As the title says, I've run into a problem where I have to call certain private functions in a class.
Public Class Class1
private Type
Private Name
private Function()
I have tried doing the following:
Public Class Class1
Dim copyClass As Class1
Public Shared Instance As Class1
Public Sub New()
MyBase.New()
copyClass = Me
End Function
Public Function createInstance() As Class1
Instance = copyClass
Return Instance
End Function
Then in my other class, Class2, I have added:
Public Property callingObject As wdCopyPatch
Get
Return copyObject
End Get
Set(value As wdCopyPatch)
copyObject = value
End Set
End Property
now, I can just do the following from within a function in Class1
Dim Ob as Class2
Ob.callingObject = createInstance()
This allows me to use copyObject from Class2 but only gives me access to Class1's Public Functions and variables. What can I do to be able to access Class1's Private functions and variables without making everything public?
Any advice or comments are appreciated :)
As per my comments, here's some code:
Sandbox is my class with a private function, and a public property getting info from that private function.
otherclass, calls this property of sandbox.
Public Class sandbox
Public ReadOnly Property myHiddenValue() As String
Get
Return get_that_sucker()
End Get
End Property
Private Function get_that_sucker()
Return "boo!"
End Function
End Class
Public Class otherClass
Public Sub mySub()
Dim mysandbox As New sandbox
MsgBox(mysandbox.myHiddenValue)
End Sub
End Class
I have been trying to do this for a long time but I can't find anything anywhere. I think I am not searching it as it should...
A little example:
Class MainClass
Property ExampleProperty As New ExamplePropertyClass
Private Class ExamplePropertyClass
Sub DoSomething()
End Sub
End Class
End Class
In the previous code the ExamplePropertyClass is used as an property of the MainClass.
There is always an error that says I can't expose a private class as propery.
But how is it possible to make only the property "Visible", I mean The user who is going to use the code should only use the property and not the class, how can the class be not inherited or visible?
What is property actually syntactic sugar for setter and getter.So mostly it is default public
You declare class as private. So it will be invisible outside. Then there is conflict if it be not visible then how people will know to assign and get that object without knowing its type. So that type should be public and visible
dim m as new MainClass()
m.ExampleProperty=? ' What is ExampleProperty ?int , object. So it should not be unknown
Another way you claim that you are not going to use that property outside.This way it is ok to have private class inside.
'Explicitly make property to be used only within class
Private Property ExampleProperty As ExamplePropertyClass
You do this with interfaces:
Public Interface IDoesSomething
Sub DoSomething()
End Interface
Public Class MainClass
Public Sub New()
m_example = New InternalClass
End Sub
Private m_example As IDoesSomething
Public ReadOnly Property Example() As IDoesSomething
Get
Return m_example
End Get
End Property
Private Class InternalClass
Implements IDoesSomething
Public Sub DoSomething() Implements IDoesSomething.DoSomething
End Sub
End Class
End Class
I can't find an answer to my question so I'm asking a new one.
I have an object where I want to fill it's properties from another class in the same solution. But the object should expose read-only properties only so the outside-caller can't see nor access the setter (cause there is no setter).
What is the best way to fill the internal backing variables from the same solution? I know I could do it in the constructor but I want to be able to set the variables after creating the object.
Sorry for my weird explaination, maybe a bit of code could help.
This is what I'm doing now:
Public Class ReadonlyObject
Protected Friend Sub New()
End Sub
'Could use this, but don't want to...
Protected Friend Sub New(foo As String)
End Sub
Friend _foo As String
Public ReadOnly Property Foo As String
Get
Return _foo
End Get
End Property
End Class
Public Class FillReadonlyObject
Private Sub DoSomeHeavyWork()
Dim roObject As New ReadonlyObject
roObject._foo = "bar"
'Could use this, but don't want to...want to access properties directly.
Dim roObject2 As New ReadonlyObject("bar")
End Sub
End Class
With this, the ReadonlyObject's properties are correctly exposed as readonly but I'm afraid it's bad practice.
I've seen implementations like this:
Public Class ReadonlyObject
Protected Friend Sub New()
End Sub
Private _foo As String
Public Property Foo As String
Get
Return _foo
End Get
Friend Set(value As String)
_foo = value
End Set
End Property
End Class
Public Class FillReadonlyObject
Private Sub DoSomeHeavyWork()
Dim roObject As New ReadonlyObject
roObject.Foo = "bar"
End Sub
End Class
This works, but exposes the property with a setter. It's not accessible, but it's visible and I don't want that :)
So maybe it's only a cosmetic thing but I think it's nice to tell the caller (or at least intellisense) the property is strictly read-only.
Thanks, Jan
If you want to explicitly declare the property as read-only, but then still have a way to set it after it is constructed, then all you need to do is create your own setter method rather than using the one automatically created for you but the property. For instance:
Public Class ReadonlyObject
Protected Friend Sub New()
End Sub
Private _foo As String
Public ReadOnly Property Foo As String
Get
Return _foo
End Get
End Property
Friend Sub SetFoo(value As String)
_foo = value
End Sub
End Class
Public Class FillReadonlyObject
Private Sub DoSomeHeavyWork()
Dim roObject As New ReadonlyObject
roObject.SetFoo("bar")
End Sub
End Class
Or, you could create two properties, like this:
Public Class ReadonlyObject
Protected Friend Sub New()
End Sub
Public ReadOnly Property Foo As String
Get
Return HiddenFoo
End Get
End Property
Friend Property HiddenFoo As String
End Class
Public Class FillReadonlyObject
Private Sub DoSomeHeavyWork()
Dim roObject As New ReadonlyObject
roObject.HiddenFoo = "bar"
End Sub
End Class
In general, according to the OOP paradigm, my understanding of encapsulation basically says:
If a member is private, it can only be accessed by the class.
If a member is protected, it can only be accessed by the base class and any derived classes.
If a member is public, it can be accessed by anyone.
If I have a nested class, can I declare a property to be accessible only to that class and the parent class it's nested within? For example:
Public Class ContainerClass
Public Class NestedClass
Protected myInt As Integer ' <- this is what I am wondering about '
Protected myDbl As Double ' <- this is what I am wondering about '
Sub New()
myInt = 1
myDbl = 1.0
End Sub
End Class
Private myNestedObject As New NestedClass
' this function is illegal '
Public Sub GrowNestedObject(ByVal multiplier As Integer)
myNestedObject.myInt *= multiplier
myNestedObject.myDbl *= multiplier
End Sub
End Class
In the example, I cannot directly access myNestedObject.myInt or myNestedObject.myDbl from an instance of ContainerClass if those members are Private or Protected. But suppose I don't want to make them Public, because then they are TOO exposed: they can be altered from anywhere, not just within a ContainerClass object. Declaring them Friend would still be too weak as that would allow them to be altered from anywhere within the application.
Is there any way to accomplish what I am going for here? If not, can anyone think of a more sensible way to achieve something like this?
There is no way of doing this directly with a combination of accessibility modifiers.
The best way I can think of doing this is as follows. It involves an extra level of indirection.
Create a Nested Interface with Private accessibility. This will give only the Parent class and nested children access
Add the fields you want access to to that interface
Make the Nested class implement the interface
Make all of the implementations have private accessibility
Now the parent class and only the parent class will have access to those properties and methods.
For Example:
Class Parent
Private Interface Interface1
ReadOnly Property Field1() As Integer
End Interface
Public Class Nested1
Implements Interface1
Private ReadOnly Property Field1() As Integer Implements Interface1.Field1
Get
Return 42
End Get
End Property
End Class
Sub New()
Dim child As Interface1 = New Nested1
Dim x = child.Field1
End Sub
End Class
Based on JaredPar's answer, you could use a Private ChildClass but a Public Interface that reveals only what it sould show :
Public Class ParentClass
Public Interface IChildClass
ReadOnly Property i() As Integer
Sub SomeSub()
End Interface
Private Class ChildClass
Implements IChildClass
Public myInt As Integer
Public ReadOnly Property i() As Integer Implements IChildClass.i
Get
Return myInt
End Get
End Property
Public Sub SomeSub() Implements IChildClass.SomeSub
End Sub
End Class
Public Shared Function GetNewChild() As IChildClass
Dim myChild = New ChildClass()
myChild.myInt = 3
Return myChild
End Function
End Class
Usage :
Dim c As ParentClass.IChildClass = ParentClass.GetNewChild()
MessageBox.Show(c.i)
c.i = 2 ' Does not compile !
c.SomeSub()