This is my first post. Please forgive me for asking a basic question as I'm new to programming.
I have following code and it just didn't compile
Module Module1
Public Sub Test
dim a as New TestClass()
dim b as string
b = a.ReturnString()
End Sub
End Module
Public Class TestClass
Public Function ReturnString() as string
Return "Hello World"
End Function
End Class
EDIT: problem solved
Lesson: Need to instantiate class before using it, many thanks to Gens and all of you!
You have 2 End Class statements, remove one.
It looks like you need to put your Test method inside a Module in order for it to Compile
Module Module1
Public Sub Test
dim a as TestClass()
dim b as string
b = a.ReturnString()
End Sub
End Module
Public Class TestClass
Public Function ReturnString() as string
Return "Hello World"
End Function
End Class
EDIT
As was pointed out by Blindy, you had double End Class statements
Try something like this
vbc <filename>.vb
with
Public Class Main
Shared Sub Main
Dim main as New Main
main.Test()
End Sub
Public Sub Test
dim a as New TestClass
dim b as string
b = a.ReturnString()
End Sub
Public Class TestClass
Public Function ReturnString() as string
Return "Hello World"
End Function
End Class
End Class
Your TestClass need to be instantiated before use. To instantiate a class, use new keyword before the class name
dim a as new TestClass()
dim b as string
b = a.ReturnString()
Related
Have two questions regarding the code below:
In the following code, the class Test implement the interface Test_Interafce. I have read in more than one articles that when a class implements an interface, we should assign the class instance to the interface. Going by that in the following code the statement Dim t As New Test() should be replaced by Dim t As Test_Interface = New Test(). However I do not understand the advantage or need for the same. When I instantiate the class Test by simply writing Dim t As New Test(), I am able to access all elements (even the procedures of the interface implemented by the class) through the instance "t" and the code seems to be working fine. So then why to assign a class instance to an interface?
Infact if I write Dim t As Test_Interface = New Test() then through "t" does not allow me to access the subroutine CHECK in the class Test. The error being displayed is: "CHECK is not a member of Test_Interface". So isnt that a disadvantage??!!
What is the use of the statement: Throw New NotImplementedException(). This statement comes automatically when I implement teh interface in a class/structure.
The code is found below:
Module Module1
Interface Test_Interface
Function Length(ByVal s As String) As Integer
Sub Details(ByVal age As Integer, ByVal name As String)
End Interface
Sub Main()
Dim t As New Test() 'Alternate definition: Dim t As Test_Interface = New Test()
t.Details(31, "Mounisha")
Console.WriteLine("Length of the string entered = {0}", t.Length("Hello"))
t.check()
Console.ReadLine()
End Sub
End Module
Class Test
Implements Test_Interface
Public Sub Details(age As Integer, name As String) Implements Test_Interface.Details
Console.WriteLine("Age of person = {0}", age)
Console.WriteLine("Name of person = {0}", name)
'Throw New NotImplementedException() ----> what does this do?
End Sub
Public Function Length(s As String) As Integer Implements Test_Interface.Length
Console.WriteLine("Original String: {0}", s)
Return s.Length()
'Throw New NotImplementedException()
End Function
Sub check()
Console.WriteLine("The sub can be accessed")
End Sub
End Class
I'm trying to communicate with a class that's already in use, something like this.
Assume "PROJECTNAME" as a namespace or the whole project
Class1:
Public Class Class1
Dim Text1 As String
Sub ChangeString(input as String)
Text1 = String
End Sub
Sub Main()
Do
' Code to prevent the Process stopping (Ignore This)
Loop
End Sub
End Class
Class 2:
Imports PROJECTNAME
Public Class Class2
Dim ForeignClass1 As New Class1
Dim ForeignClass2 As New Class1
Sub Main()
Do
'Code to prevent the Process stopping(Ignore This)
Loop
End Sub
End Class
Class 3:
Imports PROJECTNAME
Public Class Class3
Dim CustomClass As New Class2
Sub Main()
'Code here to interact between "ForeignClass2" and "ForeignClass1"
End Sub
End Class
The codes above is a concept that I'm trying to explain, not the actual code as it's a private code that I'm not suppose to expose. So what I want is to make "ForeignClass2" interact with "ForeignClass1" or make "ForeignClass1" interact with "ForeignClass2" without touching or making a new "Class1" array and just "ForeignClass1" and "ForeignClass2" only. How can I do that?
In VB, I have a class that does some standard validations. What I'd LIKE to do is to declare some variables, then create instances of a validator class that include pointers to the variables, and then at some later time execute the validators to test the values in the fields that are pointed to.
Something like this:
public class MyData
public property foo as string
public property bar as string
dim vfoo as validator
dim vbar as validator
public sub new()
vfoo=new validator(&foo) ' i.e. & operator like in C
vbar=new validator(&bar)
end sub
public sub validate()
vfoo.validate
vbar.validate
end sub
end class
public class validator
dim _field as string* ' i.e. * like in C
public sub new(field as string*)
_field=field
end sub
public sub validate
if string.isnullorempty(_field) then
throw SomeException
else if not SomeOtherTest(_field) then
throw SomeOtherException
end sub
The catch is that, to the best of my knowledge, there is nothing like C pointers in VB. Is there any reasonably easy way to do this?
At present I am passing in the field values at the time I call the validate() function, but this is not ideal because I would like to be able to create a List of validators specific to a given caller, and then loop through the List. But at the time I loop, how would I know which value from MyClass to pass in, unless I had a giant select statement keying off some "field code"? (And of course in real life, there are not just two fields like in this example, there are quite a few.)
Am I just having a brain freeze and there's an easy way to do this? Or can this not be done in VB because there are no such thing as pointers?
Like Java, VB doesn't make direct use of pointers (it compensates where it can with library/framework calls). In the context of a garbage-collected language, I can't imagine that this style of validation would work out well.
But for fun, maybe a lambda-based solution could suit?:
Public Class MyData
Public Property foo As String
Public Property bar As String
Dim vfoo As validator
Dim vbar As validator
Public Sub New()
vfoo = New validator(Function() foo)
vbar = New validator(Function() bar)
End Sub
Public Sub validate()
vfoo.validate()
vbar.validate()
End Sub
End Class
Public Class validator
ReadOnly _fieldFunc As Func(Of String)
Public Sub New(fieldFunc As Func(Of String))
_fieldFunc = fieldFunc
End Sub
Public Sub validate()
Dim _field = _fieldFunc()
If String.IsNullOrEmpty(_field) Then
Throw New Exception("NullOrEmpty")
ElseIf Not SomeOtherTest(_field) Then
Throw New Exception("SomeOtherTest")
End If
End Sub
Public Function SomeOtherTest(f As String) As Boolean
Return True
End Function
End Class
I have a main program with two classes
1- A winform that contains two elements :
Memo Edit to type some code;
Button named compile.
The end user may type some VB.Net code in the memo edit and then compile it.
2 - A simple test class :
Code :
Public Class ClassTest
Public Sub New()
MsgBox("coucou")
End Sub
End Class
Now I would like to use the class ClassTest in the code that will be typed in the MemoEdit and then compile it :
When hitting compile I recieve the error :
The reason is that, the compiler can't find the namespace ClassTest
So to summarize :
The class ClassTest is created in the main program
The end user should be able to use it and create a new assembly at run time
Does anyone know how to do that please ?
Thank you in advance for your help.
Code of the WinForm :
Public Class Form1
Private Sub SimpleButtonCompile_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles SimpleButtonCompile.Click
Dim Code As String = Me.MemoEdit1.Text
Dim CompilerResult As CompilerResults
CompilerResult = Compile(Code)
End Sub
Public Function Compile(ByVal Code As String) As CompilerResults
Dim CodeProvider As New VBCodeProvider
Dim CodeCompiler As System.CodeDom.Compiler.CodeDomProvider = CodeDomProvider.CreateProvider("VisualBasic")
Dim Parameters As New System.CodeDom.Compiler.CompilerParameters
Parameters.GenerateExecutable = False
Dim CompilerResult As CompilerResults = CodeCompiler.CompileAssemblyFromSource(Parameters, Code)
If CompilerResult.Errors.HasErrors Then
For i = 0 To CompilerResult.Errors.Count - 1
MsgBox(CompilerResult.Errors(i).ErrorText)
Next
Return Nothing
Else
Return CompilerResult
End If
End Function
End Class
Here is the solution :
If the end user wants to use internal classes he should use the command : Assembly.GetExecutingAssembly
The full code will be :
Code :
Imports System.Reflection
Imports System
Public Class EndUserClass
Public Sub New()
Dim Assembly As Assembly = Assembly.GetExecutingAssembly
Dim ClassType As Type = Assembly.GetType(Assembly.GetName().Name & ".ClassTest")
Dim Instance = Activator.CreateInstance(ClassType)
End Sub
End class
I am trying to test that a property has been set but when I write this as a unit test:
moqFeed.VerifySet(Function(m) m.RowAdded = "Row Added")
moq complains that "Expression is not a property setter invocation"
My complete code is
Imports Gallio.Framework
Imports MbUnit.Framework
Imports Moq
<TestFixture()> Public Class GUI_FeedPresenter_Test
Private moqFeed As Moq.Mock(Of IFeedView)
<SetUp()> Sub Setup()
moqFeed = New Mock(Of IFeedView)
End Sub
<Test()> Public Sub New_Presenter()
Dim pres = New FeedPresenter(moqFeed.Object)
moqFeed.VerifySet(Function(m) m.RowAdded = "Row Added")
End Sub
End Class
Public Interface IFeedView
Property RowAdded() As String
End Interface
Public Class FeedPresenter
Private _FeedView As IFeedView
Public Sub New(ByVal feedView As IFeedView)
_FeedView = feedView
_FeedView.RowAdded = "Row Added"
End Sub
End Class
I can't find any examples of moq in VB, I would be grateful for any examples.
See my question Using Moq's VerifySet in VB.NET for the solution to this.