Android Question Create Object Instance of B4A Object Using The Typename

aeric said:

edit: How do you know the parameters for the constructor? ok, it is possible.
I don't think you need to use JavaObject in this case.

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Andrew King said:

I'm unsure how to create a new instance with a passed type without using GetType() and javaobject.initializeNewInstance. Is there a better way?

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aeric said:

Here is my example.

B4X:

Public Sub CreateInstance (TypeName As String, Params() As Object) As Object
    Select TypeName
        Case "b4a.example.main$_person"
            Dim t1 As Person
            t1.Initialize
            If Params.Length > 0 Then t1.FirstName = Params(0)
            If Params.Length > 1 Then t1.LastName = Params(1)
            Return t1
        Case "b4a.example.main$_fruit"
            Dim t2 As Fruit
            t2.Initialize
            If Params.Length > 0 Then t2.Name = Params(0)
            If Params.Length > 1 Then t2.Color = Params(1)
            Return t2
        Case Else
            Return Null
    End Select
End Sub

B4X:

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

Usage:

B4X:

ShowTheObject(CreateInstance("b4a.example.main$_fruit", Array("Apple", "Green")))
ShowTheObject(CreateInstance("b4a.example.main$_person", Array("Aeric")))

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aeric said:

Here is my limit. You need an advice from Erel on this.

I don't think currently B4X has automatic constructors or polymorphism that know which parameter maps to which property.
I also don't think you can use JavaObject to call B4X custom type or class.
Lastly, I won't create a complex library like this. Sounds universally flexible but I prefer more user friendly method name for each class.

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