Understanting CLASS and properties - how to use them?

Covering Object Oriented Programming (OOP) concepts is a tall order for a simple forum post, I'll try to give an abbreviated overview. Before OOP became all the rage, there was (and still is) procedural programming. With procedural programming you would write a bunch of functions to act on data that you have. The data and the functions to work with that data were separate entities. OOP changes that by combining the data and the code. The data can be contained in the class as properties; and the code can be exposed as methods (there is some overlap between properties and methods). There are several advantages to be had with OOP, among them are:

• better data integrity, OOP (done correctly) tends to be easier to validate and maintain the associated data
• easier code reuse (theoretically) - a class is (ideally) a self-contained unit that you should be able to easily use with another project
• modularity: large, complex objects can be built from smaller simple objects. A property of an object can itself be an object (or entire collection of objects).
• there's more, but I'll stop here for now...

For an example, let's look at NXOpen's Line object:

The NX 8.5 Line object has 19 properties, among these are:

• Color: an integer value representing the color number in the NX part file cdf
• StartPoint and EndPoint: each of these is a Point3D structure (a collection of related values) which represents the start and end point, respectively.
• IsBlanked: a boolean (True/False) value representing if the line is currently hidden or not
• Layer: an integer value representing the layer number that contains the line object
• and a bunch more, but you get the idea

Line objects don't live in isolation, each line is owned by a part object. In fact, a part object may have multiple lines. When we examine the Part class in the NXOpen API reference, we see that the Part has a property called "Lines" which is defined as a LineCollection, or container that holds references to multiple line objects (a collection is similar to an array, but easier to use). We can use a "For Each" loop to examine/process each item in the collection. So if we want to change the color of every line in a given file, we could do something like the following (assume myPart is a valid reference to the part file we are interested in):


For each tempLine as Line in myPart.Lines
tempLine.Color = 82
tempLine.RedisplayObject
Next

The for each construct will automatically loop through all the items in the collection, no need to query the number in the collection to initialize the loop. Each time through the loop, the "tempLine" variable will be set to reference the current line object. We can now use the object's properties and methods to query or alter the line object as we desire.



Similarly, we can loop through the solutions in a CAE part (.sim file). The code below isn't tested (yet).


Dim basePart As BasePart = theSession.Parts.BaseWork
Dim theSimPart as CAE.SimPart
Try
theSimPart = CType(basePart, CAE.SimPart)
Catch ex as NXException
'part must not be a .sim part, warn user & exit journal
msgbox("switch to a .sim part and rerun the journal")
return
End Try

dim resultDir as string
dim resultFileName as string
For Each mySolution as CAE.SimSolution in theSimPart.Simulation.Solutions
lw.writeline("name: " & mySolution.Name)
lw.writeline("analysis type: " & mySolution.AnalysisType)
lw.writeline("group count: " & mySolution.GetGroupCount.ToString)
mySolution.GetResultFile(resultDir, resultFileName)
lw.writeline("results directory: " & resultDir)
lw.writeline("results file: " & resultFileName)
lw.writeline("")
Next



If the code above works, you can add a test to check the solution name against the name of interest and take the appropriate actions.