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inherited就是调用祖先类的函数，如果不带参数就是默认调用同名函数
如果带参数则表明子类中的函数个数可能比祖先类要多取其中的几个参数传过去
例如
祖先类有个函数 Create(AName:string);
子类有个函数 Create(AName:string;AComponent:TObject);override;
那么子类的Create函数内就可以这样调用祖先类：
procedure TAClass.Create(AName:string;AComponent:TObject);
begin
Inherited Create(AName);
end;
Inherited
Keyword |
Used to call the parent class constructor or destructor method |
|
| 1 |
Create;
begin
Inherited; // Always call at the start of a constructor
...
end; |
| 2 |
Create(arguments);
begin
Inherited Create(arguments); // Always call at the start of a constructor
...
end; |
| 3 |
Destroy;
begin
...
Inherited; // Always call at the end of a destructor
end; |
|
| |
| Description |
The Inherited keyword is used to call the parent constructor or destructor method, as appropriate, for the current class.
It is called at the start of a constructor, and at the end of a desctructor. It is not mandatory, but recommended as good practice.
Without parameters, Inherited calls the same named method the parent class, with the same parameters.
You can call a different parent method, if appropriate. |
| |
| Related commands |
| Class |
|
Starts the declaration of a type of object class |
| Constructor |
|
Defines the method used to create an object from a class |
| Destructor |
|
Defines the method used to destroy an object |
| Function |
|
Defines a subroutine that returns a value |
| Object |
|
Allows a subroutine data type to refer to an object method |
| Overload |
|
Allows 2 or more routines to have the same name |
| Override |
|
Defines a method that replaces a virtual parent class method |
| Procedure |
|
Defines a subroutine that does not return a value |
|
|
|
Example code : Examples of Inherited with and without explicit parent method names
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// Full Unit code.
// -----------------------------------------------------------
// You must store this code in a unit called Unit1 with a form
// called Form1 that has an OnCreate event called FormCreate.
unit Unit1;
interface
uses
Forms, Dialogs, Classes, Controls, StdCtrls;
type
// Define a parent class, base on TObject by default
TFruit = class
public
name : string;
Constructor Create; overload; // This constructor uses defaults
Constructor Create(name : string); overload;
end;
// Define a descendant types
TApple = class(TFruit)
public
diameter : Integer;
published
Constructor Create(name : string; diameter : Integer);
end;
// The class for the form used by this unit
TForm1 = class(TForm)
procedure FormCreate(Sender: TObject);
end;
var
Form1: TForm1;
implementation
{$R *.dfm} // Include form definitions
// Create a fruit object - parameterless version
constructor TFruit.Create;
begin
// Execute the parent (TObject) constructor first
Inherited; // Call the parent Create method
// Now set a default fruit name
self.name := 'Fruit';
end;
// Create a fruit object - parameterised version
constructor TFruit.Create(name: string);
begin
// Execute the parent constructor first
Inherited Create; // Call the parent Create method
// And save the fruit name
self.name := name;
end;
// Create an apple object
constructor TApple.Create(name: string; diameter : Integer);
begin
// Execute the parent (TFruit) constructor first
Inherited Create(name); // Call the parent method
// Now save the passed apple diameter
self.diameter := diameter;
end;
// Main line code
procedure TForm1.FormCreate(Sender: TObject);
var
fruit : TFruit;
banana : TFruit;
apple : TApple;
begin
// Create 3 different fruit objects
fruit := TFruit.Create;
banana := TFruit.Create('Banana');
apple := TApple.Create('Pink Lady', 12);
// See which of our objects are fruits
if fruit Is TFruit then ShowMessage(fruit.name +' is a fruit');
if banana Is TFruit then ShowMessage(banana.name +' is a fruit');
if apple Is TFruit then ShowMessage(apple.name +' is a fruit');
// See which objects are apples
if fruit Is TApple then ShowMessage(fruit.name +' is an apple');
if banana Is TApple then ShowMessage(banana.name +' is an apple');
if apple Is TApple then ShowMessage(apple.name +' is an apple');
end;
end.
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Fruit is a fruit
Banana is a fruit
Pink Lady is a fruit
Pink Lady is an apple
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