Community
Hi,
First, I had to say this as nothing to do with recursion, this is a simple loop statement.
To mimic the autoCAD commands, you can exit the Sub if the user escapes (this aborts the transaction and rolls back any changes) or exit the while loop and go on executing the rest of the code (commit the transaction to save the changes).
To display the changes before the transaction is commited and disposed from within the While loop, you can call the Database.TransactionManager.QueueForGraphicFlush() method.
Here's a non tested example which may contains errors (VB is not at all my prefered language)
Public Sub AddTag()
Dim doc As Document = Application.DocumentManager.MdiActiveDocument
Dim db As Database = doc.Database
Dim ed As Editor = doc.Editor
Dim opts As PromptPointOptions = New PromptPointOptions("")
Dim res As PromptPointResult
Using tr As Transaction = db.TransactionManager.StartTransaction()
Dim mSpace As BlockTableRecord = _
DirectCast(tr.GetObject(db.CurrentSpaceId, OpenMode.ForWrite), BlockTableRecord)
' Start a while loop until user pick start and end points
While True
' Prompt for start point
opts.Message = vbLf & "Select item to tag: "
res = ed.GetPoint(opts)
' Exit sub if user presses ESC or cancels command
If res.Status = PromptStatus.Cancel Then
Exit Sub
End If
' Break the while loop if user does not pick a point (Enter or right click)
If res.Status <> PromptStatus.OK Then
Exit While
End If
ptStart = res.Value
' Prompt for end point
opts.Message = vbLf & "Select tag location: "
opts.UseBasePoint = True
opts.BasePoint = ptStart
res = ed.GetPoint(opts)
' Exit if user presses ESC or cancels command
If res.Status = PromptStatus.Cancel Then
Exit Sub
End If
' Break the while loop if user does not pick a point (Enter or right click)
If res.Status <> PromptStatus.OK Then
Exit While
End If
ptEnd = res.Value
' Add the block and the leader to Model Space
Dim blockId As ObjectId = insertTagBlock()
addLeader(getLeaderIntersect(), blockId)
' Force newly added objects to display
db.TransactionManager.QueueForGraphicsFlush()
End While
tr.Commit()
End Using
About recursion, basicaly a recursive method is a method which calls itself from within its own definition.
For example, using recursion is the only way to scan a tree structure you don't the nested depth.
Here's a simple example to get all DWG files in a directory and all the sub-directories.
Imperative way (filling a List(of String) passed as argument.
Sub GetAllDwgFiles(ByVal rootFolder As String, ByVal fileNames As List(Of String))
For Each file As String In Directory.GetFiles(rootFolder, "*.dwg")
fileNames.Add(file)
Next
For Each dir As String In Directory.GetDirectories(rootFolder)
GetAllDwgFiles(dir, fileNames) '<- recursive call
Next
End Sub
Or, in a more functional style (using Linq and returning an IEnumerable(Of string))
Function GetAllDwgFiles(ByVal rootFolder As String) As IEnumerable(Of String)
Return _
Directory.GetFiles(rootFolder, "*.dwg") _
.Concat(Directory.GetDirectories(rootFolder).SelectMany(Function(dir) GetDwgFiles(dir)))
End Function
