This is a paragraph in Delphi7 Developer's Guide tells Properties.
Methods, Events, feel good, special collection
Properties, Methods, And Events
Both the vcl and clox form hierarchies of classes That Are Tied to the IDE, WHERE you
Can Develop Applications Quickly. The Classes in Both Component Libraries Are Based
ON Properties, Methods, And Events. Each Class Includes Data Members (Properties),
Functions That Operate on the data (Methods), And A Way To Interact with users of the
Class (events). The Component Library is Written in The Component Library IS Written
Delphi
Language, Although THE
VCL is based on the Windows api and clox is based on the qt widget library.
PROPERTIES
Properties Are Characteristics of An Object That Influnce Either The Visible Behavior OR OR
The Operations of the Object. for Example, The Visible Property Determines WHether AN
Object Can Be Seen in An Application Interface. Well-Designed Properties Make Your
Components Easier for Others To Use and Easier for you to maintain.
Here Are Some of The Useful Features of Properties:
Unlike Methods, Which Are ONLY AVAILABLE AT Runtime, You Can See and Change
Some Properties At Design Time and get Immediate Feedback As The Components
Change in the ident.
? You Can Access Some Properties in The Object Inspector, Where You Can Modify THE
Values of Your Object Visually. Setting Properties At Design Time Is Easier Than
Writing code and makes your code easier to maintain.
Because the data is encapsulated, it is protected and private to the actual object.
? The calls to get and set the value of profmenties can be belethods, So Special
Processing Can Be Done That INVISIBLE TOTEER OF THE OBJECT. for Example, Data
COULD RESIDE IN A TABLE, But Could Appear as a Normal Data Member to Theprogrammer.
? You can IMPLEMENT Logic That Triggers Events or Modifies Other Data Database
Access of a property. for example, changing the value of one property allowing the value of One Property May Require
You to modify another. You can change the method.
? Properties Can Be Virtual.
? A property is not restricted to a single object. Changing One Property On One Object
CAN Affect Several Objects. for Example, Setting The Checked Property On A Radio
Button Affects All of the Radio Buttons in the group.
Methods
A Method Is a Procedure That Is Always Associated with a class. Methods Define the
BEHAVIOR OF An Object. Class Methods Can Access All The Public, Protected, And
PrivateProperties and Fields of the Class and Are Commonly ReferRed To As Member
Functions. See "Controlling Access" on page 2-6 of The Component Writer's Guide.
Although Most Methods Belong to An Instance of a Class, Some Methods Belong
INSTEAD to the class type. These is caled class methods.
Events
An Event Is An Action Or Occurrence Detected by a Program. MOST Modern Applications
Are Said to Be Event-Driven, Because They Are Designed To Respond To Events. in A
Program, The Programmer Has No Way of Predicting The Exact Sequence of Actions A
User Will Perform. for Example, The User May Choose A Menu Item, Click A Button, OR
Mark Some text. You can write code to handle the events in which you are interested,
Rather Than Writing Code That Always Executes in The Same Restricted Order.
Regardless of how an event is triggered, VCL Objects Look to see if you have writewritten
Any Code to Handle That Event. if You Have, That Code Is Executed; Otherwise, The
Default Event Handling Behavior Takes Place.The Kinds of Events That Can Occur Can Be Divided Into Two Main Categories:
User Events
?Tem Events
INTERNAL EVENTS
User Events
User Events Are Actions That The User Initiates. Examples of User Events Are Onclick
(The User Clicked The Mouse), OnkeyPress (The User Pressed A Key On The Keyboard),
And OndblClick (The User Double-Clicked A Mouse Button).
System Events
System Events Are Events That The Operating System Fires for you. For example, the
Ontimer Event (Which The Timer Component Issues WHENEVER A PREDEfined Interval
Has Elapsed, The onpaint Event (a Component Or WINDOW Needs to Be RedRawn), And
SO ON. Usually, System Events Are Not Directly Initiated by a User Action.
INTERNAL EVENTS
INTERNAL EVENTS Are Events That Are Generated by the Objects in Your Application. AN
EXAMPLE OF An Internal Event Is The Onpost Event this a dataset generates for Your
Application Tells it to post the current record.
