Amazon.co.uk Review
After a fast tour of Delphi's version of the Pascal language and the files and forms used in the Delphi IDE you get an overview of object oriented programming as it relates to Delphi. There's coverage of of Delphi usage including scheduling, thread synchronisation and so on, then it's on to the language itself. Each language element is named, its syntax and a description with any gotchas noted. There's a tips and tricks section followed by example usage and pointers to related material.
This is a lot to pack in for every Delphi language element. One consequence is the need to limit the examples, which is a pity as they're often the most useful information. At the end of the book the last chapter deals with compiler directives and two appendices cover Delphi's command line tools and the separate but indispensable SysUtils unit. Delphi In A Nutshell isn't the kind of book you read in the bath, but it is one every Delphi programmer should have available when out of it.--Steve Patient
Review
Product Description
With a new name and a new focus on CORBA, database drivers, and Microsoft Back Office applications, Inprise/Borland Delphi is enjoying a resurgence, with a growing user base of programmers who use Delphi for rapid development of enterprise computing applications. Not to rest on success, the latest version of Delphi, Version 5, includes further expansion and refinement of the 3-tier application framework introduced in Delphi 4 and has resulted in a prize-winning product.
Delphi in a Nutshell is the first concise reference to Borland/Inprise Delphi available. It succinctly collects all the information you need in one easy-to-use, complete, and accurate volume that goes beyond the product documentation itself.
Delphi in a Nutshell starts with the Delphi object model and how to use RTTI (Run Time Type Information) for efficient programming. The rest of the book is the most complete Delphi Pascal language reference available in print, detailing every language element with complete syntax, examples, and methods for use. The book concludes with a look at the compiler, discussing compiler directives in depth.
About the Author
Ray Lischner began his career as a software developer, but dropped out of the corporate rat race to become an author. He started using C++ in the late 1980s, working at a company that was rewriting its entire product line in C++. Over the years, he has witnessed the evolution of C++ from cfront to native compilers to integrated development environments to visual, component-based tools. Ray has taught C++ at Oregon State University. He is the author of Delphi in a Nutshell and O'Reilly's upcoming C++ in a Nutshell, as well as other books.
Excerpted from Delphi in a Nutshell by Ray Lischner. Copyright © 2000. Reprinted by permission. All rights reserved.
Delphi's support for object-oriented programming is rich and powerful. In addition to traditional classes and objects, Delphi also has interfaces (similar to those found in COM and Java), exception handling, and multithreaded programming. This chapter covers Delphi's object model in depth. You should already be familiar with standard Pascal and general principles of object-oriented programming.
Classes and Objects
Think of a class as a record on steroids. Like a record, a class describes a type that comprises any number of parts, called fields. Unlike a record, a class can also contain functions and procedures (called methods), and properties. A class can inherit from another class, in which case it inherits all the fields, methods, and properties of the ancestor class.
An object is a dynamic instance of a class. An object is always allocated dynamically, on the heap, so an object reference is like a pointer (but without the usual Pascal caret operator). When you assign an object reference to a variable, Delphi copies only the pointer, not the entire object. When your program finishes using an object, it must explicitly free the object. Delphi does not have any automatic garbage collection (but see the section "Interfaces," later in this chapter).
For the sake of brevity, the term object reference is often shortened to object, but in precise terms, the object is the chunk of memory where Delphi stores the values for all the object's fields. An object reference is a pointer to the object. The only way to use an object in Delphi is through an object reference. An object reference usually comes in the form of a variable, but it might also be a function or property that returns an object reference.
A class, too, is a distinct entity (as in Java, but unlike C++). Delphi's representation of a class is a read-only table of pointers to virtual methods and lots of information about the class. A class reference is a pointer to the table. (Chapter 3, Runtime Type Information, describes in depth the layout of the class tables.) The most common use for a class reference is to create objects or to test the type of an object reference, but you can use class references in many other situations, including passing class references as routine parameters or returning a class reference from a function. The type of a class reference is called a metaclass.
Example 2-1 shows several class declarations. A class declaration is a type declaration that starts with the keyword class. The class declaration contains field, method, and property declarations, ending with the end keyword. Each method declaration is like a forward declaration: you must implement the method in the same unit (except for abstract methods, which are discussed later in this chapter).
Example 2-1: Examples of Classes and Objects
type
TAccount = class
private
fCustomer: string; // name of customer
fNumber: Cardinal; // account number
fBalance: Currency; // current account balance
end;
TSavingsAccount = class(TAccount)
private
fInterestRate: Integer; // annual percentage rate, scaled by 1000
end;
TCheckingAccount = class(TAccount)
private
fReturnChecks: Boolean;
end;
TCertificateOfDeposit = class(TSavingsAccount)
private
fTerm: Cardinal; // CD maturation term, in days
end;
var
CD1, CD2: TAccount;
begin
CD1 := TCertificateOfDeposit.Create;
CD2 := TCertificateOfDeposit.Create;
...
