Question

delphi如何建立自定义类

Answer 1

这个话题有点大。贴个Delphi的帮助信息给你吧。
如果你不能完全理解，说明你对 Delphi 的语法以及面向对象编程方面的知识还需要进一步积累。加油

A class type must be declared and given a name before it can be instantiated. (You cannot define a class type within a variable declaration.) Declare classes only in the outermost scope of a program or unit, not in a procedure or function declaration.

A class type declaration has the form

type className = class (ancestorClass)
memberList
end;

where className is any valid identifier, (ancestorClass) is optional, and memberList declares members--that is, fields, methods, and properties--of the class. If you omit (ancestorClass), then the new class inherits directly from the predefined TObject class. If you include (ancestorClass) and memberList is empty, you can omit end. A class type declaration can also include a list of interfaces implemented by the class; see Implementing interfaces.

Methods appear in a class declaration as function or procedure headings, with no body. Defining declarations for each method occur elsewhere in the program.

For example, here is the declaration of the TMemoryStream class from the Classes unit.

type
TMemoryStream = class(TCustomMemoryStream)
private
FCapacity: Longint;
procedure SetCapacity(NewCapacity: Longint);
protected
function Realloc(var NewCapacity: Longint): Pointer; virtual;
property Capacity: Longint read FCapacity write SetCapacity;
public
destructor Destroy; override;
procedure Clear;
procedure LoadFromStream(Stream: TStream);

procedure LoadFromFile(const FileName: string);
procedure SetSize(NewSize: Longint); override;
function Write(const Buffer; Count: Longint): Longint; override;
end;

TMemoryStream descends from TStream (in the Classes unit), inheriting most of its members. But it defines--or redefines--several methods and properties, including its destructor method, Destroy. Its constructor, Create, is inherited without change from TObject, and so is not redeclared. Each member is declared as private, protected, or public (this class has no published members); for explanations of these terms, see Visibility of class members.

Given this declaration, you can create an instance of TMemoryStream as follows:

var stream: TMemoryStream;
stream := TMemoryStream.Create;