Lesson 3 Report

John Middendorf

In Lesson 3 we learned program flow methods, including the conditional “if then” statements, and the  “for, next” and “do while, next” looping.  We were given three programming assignments using the Visual Basic component of ArcMap.  The first, to update the table of contents involved delving into the ArcGISDevHelp files, and the desktop Object Model Diagrams in order to determine the proper interface to link with the task desired to be performed. 

Discovering the proper interface, and the method of “chaining” objects in order to get there, and link the parent objects to the interface, is one of the more challenging aspects of working with ArcObjects.  The OMD’s are nearly impossible to follow on a small computer screen (a poster of a few of the main OMD pages would be a nice addition to this class), so the developer help is often more useful.  As a suggestion to ESRI, perhaps they could publish a broad outline of all the main classes, coclasses, and interfaces, and how they link, without the methods and properties.  Once the proper chaining is determined, then the user could search for the objects and interfaces to determine the methods using the developer help.

Next we wrote a simple program to truncate a string and convert letters to uppercase, requiring a separate function.  Finally, we enhanced the zoom command that we created in Lesson 2.  Each segment of this course reinforces proper programming techniques, and only through trial and error can the numerous pitfalls be discovered.  The most challenging aspect to learning how objects relate to eachother, and researching the proper interfaces to use for a particular task.