shared lib: conversion-lib in Plasma

[Aaron J. Seigo]

On Tuesday 28 July 2009, Petri Damstén wrote:
> Which I removed, since I can't see how it could work if Unit is KSharedPtr.
> Converter has UnitCategories which has Units. Category takes care of
> creating and deleting units. If Unit is deleted outside category (by
> KSharedPtr or otherwise) categories will fail. Values only have pointer to
> unit.

problem is that this is very brittle. it means new units can never be 
dynamically added/removed safely, but more importantly if the units are to be 
cleaned up at some point (which i think they do, as noted in the previous 
email) then handing around the same naked pointer amongst various classes is 
just asking for a dangling pointer to appear somewhere.

since UnitCategory keeps a reference to the Unit in its two maps[1], if they 
were KSharedPtrs instead they'd stay in reference until the UnitCategory went 
away. the UnitCategory would then be in clear ownership of the Unit objects 
and control their life-span.

[1] btw, all the calls to keys() and values() in UnitCategory really ought to 
be changed to something else; both of those calls iterate through the 
collections and create a whole new collection. having a simple collection 
(e.g. a List or a Set) of KSharedPtr<Unit> would prevent all the calls to 
values, for instance.

-- 
Aaron J. Seigo
humru othro a kohnu se
GPG Fingerprint: 8B8B 2209 0C6F 7C47 B1EA  EE75 D6B7 2EB1 A7F1 DB43

KDE core developer sponsored by Qt Software
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