I'm trying to make a game using vb,so i made this class:
Imports Microsoft.VisualBasic.PowerPacks
Module EntityI
Public entities As List(Of Entity)
Public Function getEntity(ByVal uuid As Guid) As Entity
For i = 0 To entities.Count - 1
If entities.Item(i).getUUID = uuid Then
Return entities.Item(i)
End If
Next
Return Nothing
End Function
End Module
Public Class Entity
Private uuid As Guid
Private location As Location
Private shape As OvalShape
Public Sub New()
uuid = System.Guid.NewGuid
Dim canvas As New PowerPacks.ShapeContainer
canvas.Parent = Game
shape = New OvalShape With {.Parent = canvas}
shape.SetBounds(50, 50, 50, 50)
save()
End Sub
Public Function getUUID() As Guid
Return uuid
End Function
Public Function getLocation() As Location
Return location
End Function
Public Sub teleport(ByVal location As Location)
Me.location = location
End Sub
Private Sub save()
entities.add(Me)
End Sub
End Class
So this gives an error at entities.add(Me) (NullRefernceException).
Is it something with the list or something else?
Help please.
You need to have
Public entities As New List(Of Entity)
You are new list. You are only declaring the variable as a list. Change Public entities As List(Of Entity) to Public entities As New List(Of Entity)
Related
I'm trying to make a application, in this application I have a List(of T) collection that holds an object.
When processing the object I need to know it's Index from the list.
Example:
Public Class
Public oList as New List(of TestObject)
Private Sub Test()
Dim NewObject As New TestObject
oList.add(NewObject)
Index(NewObject)
End Sub
Private Sub Index(Byval TestObject As TestObject)
debug.print(Testobject.index)
End Sub
End Class
Is something like this possible? Ive seen it available in a reference file I used some time ago, but now I would like to make this available within my own class.
Can someone provide a sample?
PS: I know I can get the index using the List(Of T).IndexOf Method (T) but for future possibilities I would like to make the call from the object itself.
What usually happen is that they have a custom list, they don't directly used List(Of T) and store the list inside the object when they add that item to the list.
Module Module1
Sub Main()
Dim someList As New CustomList
someList.Add(New CustomItem())
someList.Add(New CustomItem())
someList.Add(New CustomItem())
Console.WriteLine(someList(1).Index)
Console.ReadLine()
End Sub
End Module
Class CustomItem
' Friend since we don't want anyone else to see/change it.
Friend IncludedInList As CustomList
Public ReadOnly Property Index
Get
If IncludedInList Is Nothing Then
Return -1
End If
Return IncludedInList.IndexOf(Me)
End Get
End Property
End Class
Class CustomList
Inherits System.Collections.ObjectModel.Collection(Of CustomItem)
Protected Overrides Sub InsertItem(index As Integer, item As CustomItem)
If item.IncludedInList IsNot Nothing Then
Throw New ArgumentException("Item already in a list")
End If
item.IncludedInList = Me
MyBase.InsertItem(index, item)
End Sub
Protected Overrides Sub RemoveItem(index As Integer)
Me(index).IncludedInList = Nothing
MyBase.RemoveItem(index)
End Sub
End Class
It looks like this
Public oList As New List(Of TestObject)
Private Sub Test()
Dim NewObject As New TestObject(oList.Count)
oList.add(NewObject)
End Sub
Public Class TestObject
Public index As Integer
Public Sub New(IndxOfObj As Integer)
Me.index = IndxOfObj
End Sub
End Class
If you necessarily need to have it as a property on the object I would suggest the following:
Public Class Main
Public oList As New List(Of TestObject)
Public Sub New()
' This call is required by the designer.
InitializeComponent()
' Add any initialization after the InitializeComponent() call.
Dim NewObject As New TestObject(Me)
oList.Add(NewObject)
Dim NewObject2 As New TestObject(Me)
oList.Add(NewObject2)
MsgBox(NewObject2.Index)
End Sub
Public Function Index(ByVal TestObject As TestObject) As Integer
Return oList.IndexOf(TestObject)
End Function
End Class
Public Class TestObject
Private _main As Main
Public ReadOnly Property Index() As Integer
Get
Return _main.Index(Me)
End Get
End Property
Public Sub New(RootClass As Main)
_main = RootClass
End Sub
End Class
If you happen to have the Main class as a Singleton you can skip the whole sending 'Me' into the constructor business. Then you can just call Main.Index without storing it as a property on all TestObjects.
I have a class, it looks like this:
Public Class DataPoint
Private _data As Integer
Private _locInText As Integer
Private _searchValue As String
Property Data As Integer
Get
Return _data
End Get
Set(value As Integer)
_data = value
End Set
End Property
Property LocInText As Integer
Get
Return _locInText
End Get
Set(value As Integer)
_locInText = value
End Set
End Property
Property SearchValue As String
Get
Return _searchValue
End Get
Set(value As String)
_searchValue = value
End Set
End Property
End Class
I then create another class using this class.
Public Class PaintData
Public Time As TimeSpan
Public Color As DataPoint
Public Job As New DataPoint
Public MaxCurrent As New DataPoint
End Class
I want to create default values of some of the properties, namly SearchValue and LocInText. To me, it makes sense to do this inside the class definition, because these are essentially constants.
Q1. Should I be doing it this way? If not, what is the proper technique.
Q2. I can't get the syntax right. Can you help?
Public Class PaintData
Public Time As TimeSpan
Public Color As DataPoint
Public Job As New DataPoint
Public MaxCurrent As New DataPoint
Color.LocInText = 4 '<----Declaration expected failure because I'm not in a method
Job.LocInText = 5 '<----Declaration expected failure because I'm not in a method
End Class
Thanks all
Give DataPoint a constructor:
Public Class DataPoint
Private _data As Integer
Private _locInText As Integer
Private _searchValue As String
Public Sub New(locInText as Integer)
_locInText = locInText
End Sub
'...
End Class
And use that:
Public Class PaintData
Public Time As TimeSpan
Public Color As New DataPoint(4)
Public Job As New DataPoint(5)
Public MaxCurrent As New DataPoint(6)
End Class
Alternatively you could use
Public Property Color As DataPoint = New DataPoint With {.LocInText = 4}
in your class definition. This syntax is arguably more readable than the constructor syntax.
I have a simple class List.vb which is the following:
Public Class List
Public fList As List(Of Integer)
Public Sub New()
fList = New List(Of Integer)
fList.Add(1)
fList.Add(2)
fList.Add(3)
fList.Add(4)
fList.Add(5)
End Sub
End Class
The Console application is using this class like the following:
Module Module1
Sub Main()
Dim fObject As List = New List
Dim cnt As Integer = 0
For Each x As Integer In fObject.fList
Console.WriteLine("hello; {0}", fObject.fList.Item(cnt).ToString())
cnt = cnt + 1
Next
Console.WriteLine("press [enter] to exit")
Console.Read()
End Sub
End Module
Can I change the class code so that List.vb is a list(of integer) type?
This would mean that in the Console code I could replace In fObject.fList with just In fObject?
Or am I barking up the wrong tree - should classes be single objects and lists should be collections of classes ?
Yes, you can do that. In order for an object to be compatible with For Each, it must have a GetEnumerator function:
Public Function GetEnumerator() As IEnumerator _
Implements IEnumerable.GetEnumerator
Return New IntListEnum(fList)
End Function
The IntListEnum class must, in turn, implement IEnumerator, like this:
Public Class IntListEnum Implements IEnumerator
Private listInt As List(Of Integer)
Dim position As Integer = -1
Public Sub New(ByVal fList As List(Of Integer))
listInt = fList
End Sub
Public Function MoveNext() As Boolean Implements IEnumerator.MoveNext
position = position + 1
Return (position < listInt.Count)
End Function
Public Sub Reset() Implements IEnumerator.Reset
position = -1
End Sub
Public ReadOnly Property Current() As Object Implements IEnumerator.Current
Get
Try
Return listInt(position)
Catch ex As IndexOutOfRangeException
Throw New InvalidOperationException()
End Try
End Get
End Property
End Class
Now you can make fList private, and iterate your List as follows:
For Each x As Integer In fObject
You can see a complete example here.
The answer that dasblinkenlight has provided is excellent, but if all you need is a list that of integers that is pre-populated, you can just inherit from List(Of Integer) and then have the class populate itself in the constructor:
Public Class List
Inherits List(Of Integer)
Public Sub New()
Add(1)
Add(2)
Add(3)
Add(4)
Add(5)
End Sub
End Class
When you inherit from List(Of Integer), your class automatically gets all of the functionality implemented by that type, so your class also becomes a list class that works the same way. Then, you can just use it like this:
Dim fObject As New List()
For Each x As Integer In fObject
Console.WriteLine("hello; {0}", x)
Next
I’m working on some partial classes but I can’t figure out how to do it.
This is my classes:
Partial Public Class Form
Private InfoField() As Info
Private FormgroupField() As FormGroup
Private tittle As String
Public Property Info() As Info()
Get
Return Me. InfoField
End Get
Set
Me. InfoField = value
End Set
End Property
Public Property FormGroup() As FormGroup()
Get
Return Me.GromGroupField
End Get
Set
Me.FormGroupField = value
End Set
End Property
Public Property tittle() As String
Get
Return Me.tittleField
End Get
Set
Me.tittleField = value
End Set
End Property
End class
Partial Public Class Info
Private ChangeFormField() As ChangeForm
Private formYearField() As FormYea
Private idField As String
Public Property ChangeForm() As ChangeForm()
Get
Return Me.changeFormField
End Get
Set
Me.changeFormField = value
End Set
End Property
Public Property FormYear() As FormYear()
Get
Return Me.formYearField
End Get
Set
Me.formYearField = value
End Set
End Property
Public Property id() As String
Get
Return Me.idField
End Get
Set
Me.idField = value
End Set
End Property
End Class
Partial Public Class ChangeForm
Private idField As String
Private valueField As String
<properties goes here>
End Class
Partial Public Class FormYear
Private idField As String
Private valueField As String
<properties goes here>
End Class
And for the class FormGroup the organization is the same.
I want to build partial classes to extend these classes, so when I use all this classes in another project I only have to deal with (see) the topmost class (Form) and not the other classes (like Info and FormGroup. This is what I like to do:
Partial Public Class Form
Public Sub Init()
Me.Info = New Info
Me.FormGroup = New FormGroup
Me.Info.Init()
Me.FormGroup.Init()
End Sub
End Class
Partial Public Class Info
Public Sub Init()
Me.FormYear = New FormYear
Me.ChangeForm = New ChangeForm
Me.changeForm.Init()
End Sub
But I can’t write
Me.Info = New Info
Me.FormGroup = New FormGroup
because it is arrays with classes. How can I do it in my Form and Info class?
Thanks in advance.
You must first create an array, then loop over the array and assign each element. Also, unless you have a good, strong reason, do this in the constructor rather than a separate init method.
Public Class Form
Public Sub New()
'In VB, you give the max index, not the length.
'I prefer listing this as (whatever I want for length) - 1
Me.Info = New Info(size - 1) {}
For i = 0 to size - 1
Me.Info(i) = New Info()
Next
'similarly for other fields
End Sub
End Class
Alternatively, if you find yourself with a lot of array fields, and they all have default constructors, you could create a FixedCollection class that would encapsulate the repetitive initialization code.
Public Class FixedCollection(Of T As New)
Inherits Collection(Of T)
Public Sub New(ByVal size As Integer)
MyBase.New(New T(size - 1) {})
For i = 0 to size - 1
Me.Items(i) = New T()
Next
End Sub
'alternate constructors if you need additional initialization
'beyond construction of each element
Public Sub New(ByVal size As Integer, ByVal creator As Func(Of T))
MyBase.New(New T(size - 1) {})
If creator Is Nothing Then Throw New ArgumentNullException("creator")
For i = 0 to size - 1
Me.Items(i) = creator()
Next
End Sub
'this overload allows you to include the index in the collection
'if it would matter to creation
Public Sub New(ByVal size As Integer, ByVal creator As Func(Of Integer, T))
MyBase.New(New T(size - 1) {})
If creator Is Nothing Then Throw New ArgumentNullException("creator")
For i = 0 to size - 1
Me.Items(i) = creator(i)
Next
End Sub
'other collection overrides as needed here
End Class
EDIT: Added constructor overloads for when an element constructor is not enough.
If you only use the constructors with a creator parameter, you could remove the New constraint on T.
Use the overloads as follows:
Public Class Form
Private InfoField As New FixedCollection(Of Info)(10,
Function()
Dim ret As New Info()
ret.Init()
End Function)
End Class
Based on your comments, it seems like the Init methods are an unfortunate necessity. If possible, I would recommend that you find a way to get the generated constructor changed to call this method (defined in the generated code using partial methods) for you rather than forcing you to call it yourself.
You can initialize an Array of a Class like this:
Public FieldTypes As FieldTypeInfo() =
{
New FieldTypeInfo("Byte", 1),
New FieldTypeInfo("Int16", 2),
New FieldTypeInfo("Int32", 3),
New FieldTypeInfo("Integer", 3),
New FieldTypeInfo("Int64", 4),
New FieldTypeInfo("UInt16", 5),
New FieldTypeInfo("UInt32", 6),
New FieldTypeInfo("UInteger", 6),
New FieldTypeInfo("UInt64", 7)
}
I posted a similar question before, which worked in C# (thanks to the community), but the actual problem was in VB.Net ( with option strict on). Problem is that tests are not passing.
Public Interface IEntity
Property Id() As Integer
End Interface
Public Class Container
Implements IEntity
Private _name As String
Private _id As Integer
Public Property Id() As Integer Implements IEntity.Id
Get
Return _id
End Get
Set(ByVal value As Integer)
_id = value
End Set
End Property
Public Property Name() As String
Get
Return _name
End Get
Set(ByVal value As String)
_name = value
End Set
End Property
End Class
Public Class Command
Public Sub ApplyCommand(ByRef entity As IEntity)
Dim innerEntity As New Container With {.Name = "CommandContainer", .Id = 20}
entity = innerEntity
End Sub
End Class
<TestFixture()> _
Public Class DirectCastTest
<Test()> _
Public Sub Loosing_Value_On_DirectCast()
Dim entity As New Container With {.Name = "Container", .Id = 0}
Dim cmd As New Command
cmd.ApplyCommand(DirectCast(entity, IEntity))
Assert.AreEqual(entity.Id, 20)
Assert.AreEqual(entity.Name, "CommandContainer")
End Sub
End Class
The same is true in VB as in C#. By using the DirectCast, you're effectively creating a temporary local variable, which is then being passed by reference. That's an entirely separate local variable from the entity local variable.
This should work:
Public Sub Losing_Value_On_DirectCast()
Dim entity As New Container With {.Name = "Container", .Id = 0}
Dim cmd As New Command
Dim tmp As IEntity = entity
cmd.ApplyCommand(tmp)
entity = DirectCast(tmp, Container)
Assert.AreEqual(entity.Id, 20)
Assert.AreEqual(entity.Name, "CommandContainer")
End Sub
Of course it would be simpler just to make the function return the new entity as its return value...