Accessing iProperties

Probably the most used area of Inventor’s API is iProperties and because of that it generates more questions than any other single area.  I wanted to try and eliminate some of those questions by giving a brief overview of how to access iProperties that I hope will answer most questions.  Because iProperties is relatively simple it’s also a very good introduction to Inventor’s API.  In the example below we’ll look at what it takes to edit the value of the Part Number property.

iProperty Object Model
When working with Inventor’s API you need to be aware of the Object Model.  The object model describes the relationship between the various API objects and is used to understand how to gain access to a particular object.  Inventor’s entire object model is quite large and can be a bit overwhelming, which can be seen below.  (Click the picture to access the pdf file of the entire chart.)

However, when programming with Inventor you don’t need to understand the entire object model, but just the portion of the model that you’re currently using.  When working with iProperties you’ll be using a maximum of only six different objects.  A simplified version of the object model for these six objects is shown below.

The Application object is the top-level object and represents Inventor.  From it you can get the Documents object which provides the ability to access any open documents and also to open documents and create new documents.  The Document object represents any of the various Inventor documents, i.e. part, assembly, drawing, etc.  From the object model chart we learn that the PropertySets object is accessed from a document.  This implies that properties are owned by a document and each document has its own unique set.

Accessing a Document
There are several ways to access a specific document but for this example I’ll keep it simple by accessing the document that’s currently open for edit.  This is also the most common way of accessing a document.  You do this by using the ActiveDocument property of the Application object.  Looking at the object model chart above, using this property takes you from the Application object and jumps directly to the Document object, bypassing the Documents object.  The code for this is shown below.

Public Sub ReadiProperty()          ' Get the active document.           Dim oDoc As Document           Set oDoc = ThisApplication.ActiveDocument       End Sub

Accessing iProperties
From each document you can access its associated iProperties.  iProperties are organized in groups and the API provides access to these groups.  The first iProperty related object is the PropertySets object.  You can think of the PropertySets object as the equivalent to the iProperties dialog.  It’s the top level that provides access to all iProperty information.

The code below shows how to get the PropertySets object.

Public Sub ReadiProperty()          ' Get the active document.              Dim oDoc As Document           Set oDoc = ThisApplication.ActiveDocument                 ' Get the PropertySets object.              Dim oPropSets As PropertySets           Set oPropSets = oDoc.PropertySets       End Sub

The next object in the object model is the PropertySet object.  You can think of this object as being equivalent to a tab in the iProperties dialog. 

There’s a little more to worry about when accessing the PropertySet object because you have to specify which of the existing PropertySet objects you want.  There are a few different ways to do this but I would recommend using the name of the PropertySet.  This makes your code easier to read later.  The names of the standard property sets are:

Inventor Document Summary Information
Inventor Summary Information
Design Tracking Properties
Inventor User Defined Properties

For this sample I want to get the value of the Part Number property.  This is in the “Design Tracking Properties” property set (as determined by looking at the chart at the end of this post).  The code below illustrates getting this property set by name.

Public Sub ReadiProperty()          ' Get the active document.              Dim oDoc As Document           Set oDoc = ThisApplication.ActiveDocument                 ' Get the PropertySets object.              Dim oPropSets As PropertySets           Set oPropSets = oDoc.PropertySets                 ' Get the design tracking property set.              Dim oPropSet As PropertySet           Set oPropSet = oPropSets.Item("Design Tracking Properties")       End Sub

The next object is the Property object.  This represents a specific property, as illustrated below.

Properties are also identified by name.  The code below demonstrates accessing the part n
umber property.

Public Sub ReadiProperty()          ' Get the active document.              Dim oDoc As Document           Set oDoc = ThisApplication.ActiveDocument                 ' Get the PropertySets object.              Dim oPropSets As PropertySets           Set oPropSets = oDoc.PropertySets                 ' Get the design tracking property set.              Dim oPropSet As PropertySet           Set oPropSet = oPropSets.Item("Design Tracking Properties")                 ' Get the part number iProperty.              Dim oPartNumiProp As Property           Set oPartNumiProp = oPropSet.Item("Part Number")       End Sub

Once you have a Property object you can use its Value property to get its current value and to also set the value is you want to change the iProperty.  The code below displays the part number of the active document in a message box.

Public Sub ReadiProperty()          ' Get the active document.              Dim oDoc As Document           Set oDoc = ThisApplication.ActiveDocument                 ' Get the PropertySets object.              Dim oPropSets As PropertySets           Set oPropSets = oDoc.PropertySets                 ' Get the design tracking property set.              Dim oPropSet As PropertySet           Set oPropSet = oPropSets.Item("Design Tracking Properties")                 ' Get the part number iProperty.              Dim oPartNumiProp As Property           Set oPartNumiProp = oPropSet.Item("Part Number")                 ' Display the value.              MsgBox "The part number is: " & oPartNumiProp.Value       End Sub

This code changes the value of the part number property.

Public Sub SetiProperty()          ' Get the active document.              Dim oDoc As Document           Set oDoc = ThisApplication.ActiveDocument                 ' Get the PropertySets object.              Dim oPropSets As PropertySets           Set oPropSets = oDoc.PropertySets                 ' Get the design tracking property set.              Dim oPropSet As PropertySet           Set oPropSet = oPropSets.Item("Design Tracking Properties")                 ' Get the part number iProperty.              Dim oPartNumiProp As Property           Set oPartNumiProp = oPropSet.Item("Part Number")                 ' Set the part number.              oPartNumiProp.Value = "SamplePart001"       End Sub

Accessing an iProperty is simply of a matter of navigating down the object model to get to a specific Property object.  The tricky parts is knowing which property set the property you want is located in, and knowing the name of that property set and the name of the property.  The table below lists all of the standard property sets and the names of the properties they contain.  This should provide all you need to access existing properties.  In addition to the names, the chart also lists the type of each property.  This is important when setting the value of a property so you know what type is expected.