Android Question Create Object Instance of B4A Object Using The Typename

Daestrum said:

Couldn't you just use the JavaObject library?

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Andrew King said:

I don't want to use stringutils or any other library. I have a specific need for doing it this way. I've coded this in VB.net with ease but b4x doesnt have a GetType(Type) function or Type as Type.

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drgottjr said:

the problem with b4x's gettype(object) is that it returns a string. i think op wants to capture the object's type (not its stringified representation) and then use it later in some method which uses the type (not a string) as the passed parameter. if i understand what he wants, and i'm not sure i do. i don't understand whether he's looking for an instance of b4a.example.fruit or an instance of "b4a.example.fruit"

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aeric said:

B4X:

Dim Mango As Fruit
Mango.Initialize
Mango.Name = "Mango"
Mango.Origin = "Thailand"
Log(GetType(Mango))            ' b4a.example.main$_fruit

Dim Durian As TropicalFruit
Durian.Initialize
Durian.Name = "Musang King"
Durian.Origin = "Malaysia"
Log(GetType(Durian))           ' b4a.example.tropicalfruit

Dim afruit As Object
afruit = Durian
If GetType(afruit) = "b4a.example.tropicalfruit" Then
    MsgboxAsync("I love Tropical Fruit", afruit.As(TropicalFruit).Name)
End If

View attachment 158536

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Andrew King said:

So now I want to create an instance of this tropicalfruit or fruit not at compile time but at runtime.

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aeric said:

so now you are asking a new question?

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aeric said:

so now you are asking a new question?

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Andrew King said:

I want to create a class

B4X:

Public Class Fruit
    Public Name as string
    Public Color as string
End Class

Then I want to have one function that gets the type

B4X:

Dim typeName as string = GetType(fruit)

Then I want to have another function I can pass the type to and create an instance

B4X:

Sub CreateInstance(PassedType as string) as object
    Dim obj as object
    'code goes here to cast the object into the passedtype
    return obj
End Sub

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Andrew King said:

In vb.net I can:

VB.NET:

Public Class Fruit
    Public Property Name as string
    Public Property Color as string
End Class

Public Class Person
    Public Property FirstName as string
    Public Property LastName as string
End Class

Public Module Main
    Public Function RandomObject() as object
        Dim obj as object

        Dim rand = random.next(0,1)

        Select case rand
            case 0
                CreateInstance(gettype(Fruit))
            case 1
                CreateInstance(gettype(Person))
        End Case
   
        Return obj
    End Function

    Public Function CreateInstance(type as type) as Object
        Dim obj = Activator.CreateInstance(type)
        Return obj
    End Function

End Module

I'm trying to do something exactly like this in b4A. Something like vb.net's activator.createinstance. There is JavaObject.InitializeNewInstance but it returns a JavaObject. How to convert this javaobject into a b4a object? Or what other function can create an instance of a b4a object by providing the type or typeName?

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TxtName.Text = "B4X"
ShowTheObject(RandomObject)

Sub RandomObject As Object
    Select Rnd(0, 2)
        Case 0
            Return CreateFruit(TxtName.Text, "", "")
        Case Else
            Dim someone As Person
            someone.Initialize
            someone.FirstName = TxtName.Text
            Return someone
    End Select
End Sub

Sub ShowTheObject (obj As Object)
    Select GetType(obj)
        Case "b4a.example.person"
            MsgboxAsync("The person first name is " & obj.As(Person).FirstName, "Person")
        Case "b4a.example.main$_fruit"
            MsgboxAsync("The fruit name is " & obj.As(Fruit).Name, "Fruit")
    End Select
End Sub

Andrew King said:

I believe the solution is:

B4X:

Public Sub CreateInstance(TypeName As String, Params() As Object) As Object
    Dim jo As JavaObject
    Return jo.InitializeNewInstance(TypeName,Params).As(Object)
End Sub

Thanks to aeric for his examples that led me to the solution. Thank you all for your help and time

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