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Tip: Temporary FolderItems

Sometimes we need to deal with temporary FolderItem instances, and in those cases it would be great to not have to care about when they get out of scope in order to delete them. Wouldn’t it be great to automate that task? Continue reading and you’ll see how easy it is to implement this!

In order to instruct a FolderItem to delete itself when it’s out of scope, we will create a new class that will act as a wrapper for the FolderItem, making use of the Operator_Convert method, so we can assign a FolderItem to it and also get the underlying FolderItem wrapped in it.

So, go ahead and create a new Class. We can name it as TempFolderItem with an empty Super class in the Inspector Panel.

Add a new property to the new TempFolderItem class, using the following values in the Inspector Panel:

  • Name: mFile
  • Type: FolderItem
  • Scope: Protected

Next, let’s add a Constructor method to our class with the following signature:

  • Name: Constructor
  • Parameters: f As FolderItem
  • Scope: Public

And simply put this line of code in the associated Code Editor:

mFile = f

Then, we need to add a couple of Operator_Convert methods:

  • Name: Operator_Convert
  • Parameters: f As FolderItem
  • Scope: Public
  • Code Editor: mFile = f
  • Name: Operator_Convert
  • Returned Type: FolderItem
  • Scope: Public
  • Code Editor: Return mFile

Finally, we will add the Destructor method. This one will be in charge of deleting the underlaying FolderItem once the class instance is out of scope:

  • Name: Destructor
  • Scope: Public
  • Code Editor:

  If mfile <> Nil And mfile.Exists And mfile.IsWriteable Then

    If Not mFile.IsFolder Then



End If

Catch e As IOException
  Raise e
End Try

Temporary FolderItems in Practice

That’s all – our class definition is done! In order to test it, create a Desktop project, add the Open Event Handler to the default window and write this snippet of code in the Code Editor:

Const textContent As String = "Lorem ipsum dolor sit amet, consectetur adipiscing elit"
f = New TempFolderItem(specialfolder.desktop.child("Test.txt"))


  Var tos As TextOutputStream = TextOutputStream.Open(f)
  tos.WriteLine textContent

Catch e As IOException
End Try

Next add a new Property to the default window (Window1) using the following values in the Panel Inspector:

  • Property Name: f
  • Type: TempFolderItem
  • Scope: Public

This way, the TempFolderItem will be in Scope (this is, in memory) while the Window1 window remains opened. Once we close the window, everything will be destroyed from memory, including this property. Also the underlying FolderItem stored on it via the Destructor method of our class will be deleted.

Run the example project and see how it works. While the Window1 window remains open, our file will be available in the Desktop; but as soon we close the Window1 window… the file will be deleted automatically!

Questions? Ask me about Xojo programming on Twitter @XojoES or on the Xojo Forum.