有没有办法通过delphi中的名称实例化一个类？ [英] Is there a way to instantiate a class by its name in delphi?

问题描述

我想实例化一个类，但是我只能在一个字符串中使用它的名字。有没有办法？

解决方案

这是从Delphi帮助（Delphi 2006，但也可以从至少Delphi 7）： / p>

语法
函数GetClass（const AClassName：string）：TPersistentClass;

描述
调用GetClass从类名获取类。此类可用作需要类的例程的参数。该类必须在GetClass可以找到之前进行注册。在表单加载时，将自动注册在表单声明（实例变量）中引用的表单类和组件类。可以通过调用RegisterClass或RegisterClasses来注册其他类。

这里有一些示例代码。因为TButton是一个TControl，因此类型转换是有效的。

  procedure TForm1.FormCreate（Sender：TObject）; 
 begin 
 RegisterClasses（[TButton，TForm]）; 
结束
 
 procedure TForm1.Button1Click（Sender：TObject）; 
 var 
 CRef：TPersistentClass; 
 AControl：TControl; 
 begin 
 CRef：= GetClass（'TButton'）; 
如果CRef<> nil then 
 begin 
 AControl：= TControl（TControlClass（CRef）.Create（Self））; 
 with AControl do 
 begin 
父级：=自我; 
宽度：= 50; 
身高：= 30; 
结束
结束
结束
  

I'd like to instantiate a class but I only have its name in a string. Is there a way?

解决方案

This is from Delphi help (Delphi 2006, but also available from at least Delphi 7):

Syntax function GetClass(const AClassName: string): TPersistentClass;

Description Call GetClass to obtain a class from a class name. This class can be used as a parameter to routines that require a class. The Class must be registered before GetClass can find it. Form classes and component classes that are referenced in a form declaration (instance variables) are automatically registered when the form is loaded. Other classes can be registered by calling RegisterClass or RegisterClasses .

Here some sample code. Works as such only because TButton is a TControl and therefore the typecast is valid.

procedure TForm1.FormCreate(Sender: TObject);
begin
  RegisterClasses([TButton, TForm]);
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  CRef : TPersistentClass;
  AControl : TControl;
begin
  CRef := GetClass('TButton');
  if CRef<>nil then
  begin
     AControl := TControl(TControlClass(CRef).Create(Self));
     with AControl do
     begin
        Parent := Self;
        Width := 50;
        Height := 30;
     end;
  end;
end;

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