Delphi Programming Guide
Delphi Programmer 

Menu  Table of contents

Part I - Foundations
  Chapter 1 – Delphi 7 and Its IDE
  Chapter 2 – The Delphi Programming Language
  Chapter 3 – The Run-Time Library
  Chapter 4 – Core Library classes
  Chapter 5 – Visual Controls
  Chapter 6 – Building the User Interface
  Chapter 7 – Working with Forms
Part II - Delphi Object-Oriented Architectures
  Chapter 8 – The Architecture of Delphi Applications
  Chapter 9 – Writing Delphi Components
  Chapter 10 – Libraries and Packages
  Chapter 11 – Modeling and OOP Programming (with ModelMaker)
  Chapter 12 – From COM to COM+
Part III - Delphi Database-Oriented Architectures
  Chapter 13 – Delphi's Database Architecture
  Chapter 14 – Client/Server with dbExpress
  Chapter 15 – Working with ADO
  Chapter 16 – Multitier DataSnap Applications
  Chapter 17 – Writing Database Components
  Chapter 18 – Reporting with Rave
Part IV - Delphi, the Internet, and a .NET Preview
  Chapter 19 – Internet Programming: Sockets and Indy
  Chapter 20 – Web Programming with WebBroker and WebSnap
  Chapter 21 – Web Programming with IntraWeb
  Chapter 22 – Using XML Technologies
  Chapter 23 – Web Services and SOAP
  Chapter 24 – The Microsoft .NET Architecture from the Delphi Perspective
  Chapter 25 – Delphi for .NET Preview: The Language and the RTL
       
  Appendix A – Extra Delphi Tools by the Author
  Appendix B – Extra Delphi Tools from Other Sources
  Appendix C – Free Companion Books on Delphi
       
  Index    
  List of Figures    
  List of tables    
  List of Listings    
  List of Sidebars  

 
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Summarizing the Core VCL and BaseCLX Units

I've spent most of this chapter discussing the classes of a single unit of the library: Classes. This unit, in fact, contains most of the core classes of the library. In this section, I'll provide an overview of what's available in the Classes unit and a few other core library units.

The Classes Unit

The Classes unit is at the heart of both VCL and CLX libraries, and although it has many internal changes from the last version of Delphi, little is new for average users. (Most changes are related to modified IDE integration and are meant for expert component writers.)

Here is a list of what you can find in the Classes unit, a unit that every Delphi programmer should spend some time with:

  • Many enumerated types, the standard method pointer types (including TNotifyEvent), and many exception classes.

  • Core library classes, including TPersistent and TComponent as well as many others seldom used directly.

  • List classes, including TList, TThreadList (a thread-safe version of the list), TInterfaceList (a list of interfaces, used internally), TCollection, TCollectionItem, TOwnedCollection (which is simply a collection with an owner), TStrings, and TStringList.

  • All the stream classes I discussed in the previous section but won't list here again. There are also the TFiler, TReader, and TWriter classes and a TParser class used internally for DFM parsing.

  • Utility classes, such as TBits for binary manipulation and a few utility routines (for example, point and rectangle constructors, and string list manipulation routines such as LineStart and ExtractStrings). There are also many registration classes, to notify the system of the existence of components, classes, special utility functions you can replace, and much more.

  • The TDataModule class, a simple object container alternative to a form. Data modules can contain only nonvisual components and are generally used in database and web applications.

    Note 

    In early versions of Delphi, the TDataModule class was defined in the Forms unit; since Delphi 6 it has been moved to the Classes unit. This was done to eliminate the code overhead of the GUI classes from non-visual applications (for example, web server modules) and to better separate non-portable Windows code from OS-independent classes, such as TDataModule. Other changes relate to the data modules—for example, to allow the creation of web applications with multiple data modules.

  • New interface-related classes, such as TInterfacedPersistent, aimed at providing further support for interfaces. This particular class allows Delphi code to hold on to a reference to a TPersistent object or any descendent implementing interfaces, and is a core element of the new support for interfaced objects in the Object Inspector (see Chapter 9, "Writing Delphi Components," for an example).

  • The new TRecall class, used to maintain a temporary copy of an object. This class is particularly useful for graphical-based resources.

  • The new TClassFinder class, which is used to find a registered class instead of the FindClass method.

  • The TThread class, which provides the core operating system–independent support for multithreaded applications.

New in the Classes Unit

In Delphi 7, the Classes unit has only a few minor additions. Beside the changes I've already mentioned in this chapter, such as the extended support for name-value pairs in the TStringList class, there are a couple of new global functions, AncestorIsValid and IsDefaultPropertyValue.

Both functions were introduced to support the highlighting of non-default properties in the Object Inspector. They serve little other purpose, and I doubt you'll benefit from their use in an application—unless you are interested in saving the status of a component and form, and writing your own custom streaming mechanism.

Other Core Units

Typical Delphi programmers don't directly use the other units that are part of the RTL package as often as they use Classes. Here is a list of these other units:

  • The TypInfo unit includes support for accessing RTTI information for published properties, as discussed in the section "Accessing Properties by Name."

  • The SyncObjs unit contains a few generic classes for thread synchronization.

  • The ZLib unit includes compression and decompression streams, as discussed earlier in the section "Compressing Streams with ZLib."

  • The ObjAuto unit contains code to call the published methods of an object by name, passing the parameters in a variant array. This unit is part of the extended support for dynamic method invocation pushed by SOAP and other new Delphi technologies.

Of course, the RTL package also includes the units with functions and procedures discussed in the preceding chapter, such as Math, SysUtils, Variants, VarUtils, StrUtils, DateUtils, and so on.


 
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