Classes.RegisterClasses,Classes.FindClass,Classes.GetClass学习

procedure RegisterClasses(AClasses: array of TPersistentClass);

 AClasses是一个数组:每个类都通过调用RegisterClass注册到组件流中,删除注册的类调用UnRegisterClass(); 

function FindClass(const ClassName: string): TPersistentClass;

ClassName：要查找的类名,返回TPersistentClass类型;如果查找的类不存在则触发一个exception信息,返回的类必须是从TPersistent派生的

function GetClass(const AClassName: string): TPersistentClass;

 AClassName:类名,如果不存在返回nil,存在则返回对应的持续久化 

unit Unit2;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm2 = class(TForm)
    Edit1: TEdit;
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form2: TForm2;

implementation

{$R *.dfm}

procedure TForm2.Button1Click(Sender: TObject);
var
 myRef: TControlClass;
 testControl: TControl;
begin
   //返回类型是一个类引用
   myRef := TControlClass(Classes.GetClass(edit1.Text));

   testControl := TControl(myRef.Create(self));
   testControl.Parent := self;
    testControl.Top := 20;
   testControl.Left := 20;
   testControl.Show;
end;

//程序运行时就执行
initialization
   //注册类
  Classes.RegisterClasses([TIcon, TMemo, TButton,TMemo,TLabel]);
//程序关闭时执行
finalization
  //删除注册的类
  Classes.UnRegisterClasses([TIcon, TMemo, TButton,TMemo,TLabel]);

end.

应用:
  比如树型导航栏不用每一个节点都要写事件.增加节点等.以后会写一个例子