Re: [fpc-devel] How to force the child's constructor to call its parent constructor

[Michael Schnell]

Couldn't you check the ID in your after construction event and throw an 
exception if it's not set ?


-Michael
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Re: [fpc-devel] How to force the child's constructor to call its parent constructor

[amir]

It is a run-time error but what I am looking for is an compile-time 
error. It is not sensible(for me) to raise an exception because of bad 
implementation. Thanks for you idea ;)


Amir

Michael Schnell wrote:
Couldn't you check the ID in your after construction event and throw 
an exception if it's not set ?


-Michael
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[fpc-devel] How to force the child's constructor to call its parent constructor

[amir]

Is there any way to force the child constructor to call its 
parent(direct parent) constructor. Consider the following case:


 TParent= class (TObject)
 private
   ID: Integer;
 public
 constructor Create (MyIdentifier: Integer);

 end;

I want to force the all childs of TParent to call the Create constructor 
(with appropriate parameter). But one can implement a child class like this:

 constructor TChild.Create;
 begin
// do any thing but not use inherited.
 end;


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Re: [fpc-devel] How to force the child's constructor to call its parent constructor

[Joao Morais]

amir wrote:
I want to force the all childs of TParent to call the Create constructor 
(with appropriate parameter). But one can implement a child class like 
this:

 constructor TChild.Create;
 begin
// do any thing but not use inherited.
 end;


No way. But you can override the NewInstance method; constructors will 
call it for sure. You can also override the AfterConstruction method.


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Joao Morais
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Re: [fpc-devel] How to force the child's constructor to call its parent constructor

[amir]

Joao Morais wrote:

amir wrote:
I want to force the all childs of TParent to call the Create 
constructor (with appropriate parameter). But one can implement a 
child class like this:

 constructor TChild.Create;
 begin
// do any thing but not use inherited.
 end;


No way. But you can override the NewInstance method; constructors will 
call it for sure. You can also override the AfterConstruction method.


--
Joao Morais
How can I use the NewInstance or AfterConstruction methods for my 
purpose? I want to force the others to set ID. The TParent is written by 
me but anyone can write the TChild class.



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