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I have two classes - base class and inherited class as follows.
Base Class:
TAlarm = class(System.Object)
private:
protected:
public:
constructor (tag:TTagname);
end;
inherited class:
TAlarmMsg = class(TAlarm)
public
constructor (aname:string);
method GetAlarmMsg:string; override;
method SendMsg(msg:string);
end;
constructors:
constructor TAlarm(tag:TTagname);
begin
Tagname := tag;
end;
constructor TAlarmMsg(aname:string);
begin
inherited TAlarm(aname); <========Here is my problem.
name := aname.ToCharArray;
end;
No matter what or how I call or play around with inherited constructor, I keep getting the following error messages when I compile the source file.
- Self cannot be accessed before the inherited constructor has finished. And/OR - Cannot find appropriate constructor in base class so manual call to inherited is required
By the way, I have spent good half a day researching on this issue and have found good information online. Nothing helps so far. I even found the webpage that directly talks about constructors on Delphi Prism Wikipedia ( http://prismwiki.embarcadero.com/en/Constructors ).
So, how would you do it correctly? Thanks,
648
Delphi Basics : Inherited command DelphiBasics Inherited Keyword Used to call the parent class constructor or destructor method 1 keyword Inherited(Create; begin Inherited; // Always call at the start of a constructor end; 2 Create(arguments); begin InheritedCreate(arguments); // Always call at the start of a constructor end; 3 Destroy;
This article is about the inheritance concept in C++ and how we can inherit the base class’ constructors in the derived class. In C++, particularly in object-oriented programming, the most fundamental and widely used concept is that of inheritance.
With the help of base keyword, the derived class can call the constructor which is defined in its base class. Note: Any form of the constructor defined in the base class can be called by the base keyword, but only that constructor executes that matches the arguments.
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.
The statement
inherited constructor(aName);
should do it.
183
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