The Delphi Wizard Framework - Design Decisions

The Delphi Wizard Framework, as I introduced in the previous post, was originally designed to replace a complex configuration system which was put together using a TNotebook component (yes, from the Delphi 1 days) on a single form. The first problem this faced was adding pages was more complex than it needed to be. The second problem was re-using entire pages in another project became a copy and paste fest, with plenty of room for missing a critical event.

My first goal was to take each page out of the single form, and create a form of its own that contains all of the logic just for that page. This worked very well, but I still had the problem where each form had to be added to the uses clause, and a circular reference back to the main containing form didn't feel right. Taking my research into using interfaces outside of COM, I developed a simple interface for the "FormManager" and another for the "FormPage", named IWizardManager and IWizardPage respectfully. When each page is displayed, the formmanager would pass forward its reference and the page would record this for later use.

With that out of the way, I then turned to how to let the system know about each form. I decided that the best way to address that problem would be to use the class registry system already existing in Delphi and call RegisterClass(classname) for each form that will be used. This cuts back on the need to add each unit to the uses clause and makes reuse almost as simple as adding the form to the project. I say almost, as the default behavior of Delphi when a form is added to the project is to auto-create it...this is not necessary with the framework as the framework will be responsible for the creation and deletion of each form.

In my next post, I will discuss form navigation.

Introducing the Delphi Wizard Framework

I just posted my latest version of my wizard framework to http://code.google.com/p/delphiwizardframework/.  

This is some general purpose code that I have found myself using in many of my projects, as most of them at some point involve the need to step a user through many different "wizard" screens.  The concept behind it is quite simple, rather than code the button clicks on each form, instead use a container to hold the form which contains the buttons.  Each "wizard page" is a separate form, and can be invoked by the classname rather than a specific class.  This allows for the wizard to be data driven, and the loose binding into the project allows for easy reuse of wizard pages in other wizards.

For those who have used my tFrameManager component in Delphi 5, will see a few simularities.

Over the next few weeks, I'll be posting further instructions on how to put the system into action, along with some advanced tricks which are not currently evident in the sample project.

Fun with Generics.collections

I guess the best way to learn about new language features are to put them in practice, and with that I jumped into using the TDictionary to keep track of some xml nodes I was editing.  It was very easy to implement, but what got me stumped was then how to iterate thru the entire list and apply changes to all of the nodes at once.

Thats when I recalled the new for ... in ... syntax.  Using it was dirt simple.  Since my collection was created as tDictionary all I had to do was create a new variable of tPair and then use the for..in.. syntax to invoke a body of code against every IXmlNode in my tDictionary.

var
  aPair : tPair<string,ixmlnode>
begin
  for aPair in fDictionary do
    aPair.Value.Attributes['dirty'] := '-1';
end;

In my option, this generates code which is much more readable and feels more natural.  Now, on to the next challenge.... finding a place in my project where I can put annoymous methods to practical use.

(EDIT: Updated syntax on variable declaration, as it was incorrect...seems the problem with generics is that they HIDE when copied to HTML.)

Google Chrome now available

Download and play with it now. http://tools.google.com/chrome/?hl=en-US

Very small footprint, very fast browser.

First look, browser has much more room compared to IE/Firefox out of the box....although my webmail provider (not Gmail of course) doesn't recognize the browser yet so it doesn't give me the rich experience I'm used too.