Suppose you get a third party component not really well written, that does not do any kind of check of its arguments (sound familiar ?). And of course, you have not paid to get the source of this crappy peace of ****

Now you was dressed up with Design By Contract in your earlies, so you take the pain to add some assertions _before_ calling the method of this component and maybe some assertions after returning from the method.

I think you then get something like this (inspired from the sample given by Marco Cantu in Essential Delphi 8 for .NET) :

Let’s the component doc says :

TMyBuggyComponent :

Text : string : blabla

procedure DoSomething(arg: TObject) : blabla…

You then could write :

<code>

uses MyBuggyComponent;

type

TMyBuggyComponentClassHelper = class Helper for TMyBuggyComponent

public

procedure DoSomething(const arg: string);

end;

procedure TMyBuggyComponentClassHelper.DoSomething(const arg: string);

begin

assert(arg <> ”);

inherited DoSomething(arg);

assert(Text <> ”);

end;

</code>

It compiles, at least :-)

Cheers,

Andrew

#1 default array properties (indexers) can be overloaded (have the same name as long as the array parameter list is "different"

#2 identifier escape char & is supported: you might have var &object: TObject;

#3 static class methods supported

#4 method directive "final" supported (check this!)

#5 method directive "inline" supported (but not for .NET !)

#6 "class" properties supported: class property InstanceCount: Integer read GetInstanceCount;

#7 Compiler hint directive "experimental" supported

#8 classes can contain "const" declarations

#9 classes can contain "class var" declarations (static fields)

#10 classes support the "abstract" and "sealed" directives

Gerrit Beuze

ModelMaker Tools

http://www.modelmakertools.com

type

TOuterClass = class

strict private

type

TInnerClass = class

end;

public

end;