[Lazarus] Controlling access to a method

Mark Morgan Lloyd markMLl.lazarus at telemetry.co.uk
Wed Jan 30 14:50:55 CET 2013

Hans-Peter Diettrich wrote:
> Mark Morgan Lloyd schrieb:
>> Given a fragment of code like this:
>> type
>>   TDbConfigFrame = class(TFrame)
>> ..
>>   public
>>     { public declarations }
>>     property DbInit: TDbConfigInit write fdbInit;
>>   end;
> A write-only property can be implemented by a (setter) procedure,

Yes, I was assuming that.

> to which you add whatever arguments may be useful (e.g. Sender).

OK, but in that case I presume that you can no longer go via the 
object's property (reserved word).

Also in that case I presume that some unauthorised caller could spoof an 
explicit sender parameter.

Is there a reliable way to walk the stack and get a list of senders? I 
presume at the very least that LineInfo would be needed for this, and 
that the executable would have to be unstripped.

>> is there any way of enforcing a rule that DbInit can only be written 
>> by (for example) a descendant of TForm or TNotebook? Or only being 
>> writable by e.g. the OnCreate() method of certain designated form 
>> instances?
> You can check Sender against the owner of the frame, if that helps.

Yes, that I like. However I think the problem is still getting the 
sender in such a way that it can't be spoofed.

Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk

[Opinions above are the author's, not those of his employers or colleagues]

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