Sven Barth wrote:
On 27.01.2012 23:51, Mark Morgan Lloyd wrote:
Sven Barth wrote:
On 27.01.2012 22:46, Mark Morgan Lloyd wrote:
If a class has a public reader property like this:
TLexemeList= class(TObject)
protected
fValue: TPrimaevalValue;
public
property Value: TPrimaevalValue read fValue;
...
Note that below is in a different unit.
is there a way of allowing a class helper to augment this with a
protected writer property? My attempt as below messed up the reader:
TLLEvaluator = class helper for TLexemeList
private
procedure SetValue(v: TPrimaevalValue);
protected
property Value: TPrimaevalValue write SetValue;
...
In your exact example fValue is protected so the following should work:
property Value: TPrimaevalValue read fValue write SetValue;
That didn't work since once we're in the helper it can't see fValue
since it's only visible in the original unit.
You are right that it does not work, but you're not right about the
reason. Helpers are able to access published, public and protected
members of its extended class (e.g. you're able to write "fValue :=
aValue" in your setter inside the helper), but you can't make use of
fields and methods of the extended class in the helper's declaration.
Obviously code in the helper can simply call SetValue(), but I thought
it worth raising in case I was missing something obvious.
What about my second suggestion?
Sorry, it was getting late and I think I missed the GetValue() detail.
property Value: TPrimaevalValue read GetValue write SetValue;
..
function TLLEvaluator.GetValue: TPrimaevalValue;
begin
Result := inherited Value;
end;
Thanks, I think that works but I need to do more testing.
--
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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