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refs #84 removed the CValueObject::compare method and added a friend function BlackMisc::compare to replace it.

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The new compare is implemented using "multimethods" described in the book Advanced C++ Programming Styles and Idioms by James Coplien.

First, the isA method is used to determine which of the values being compared is the most general. (For example, CLength is more general than CAltitude.)
Then the compareImpl method is called on the most general value, with the other value as an argument.
If there is not a direct inheritance relation between the two values (or they are the same class) then the comparison is invalid and a assert is triggered.
This commit is contained in:
Mathew Sutcliffe
2014-01-14 00:45:19 +00:00
parent e40c93fe1b
commit db4c05dd9f
48 changed files with 1015 additions and 119 deletions
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31
src/blackmisc/geoearthangle.cpp
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@@ -71,17 +71,34 @@ namespace BlackMisc
return LATorLON(a);
}
/*
* metaTypeId
*/
template <class LATorLON> int CEarthAngle<LATorLON>::getMetaTypeId() const
{
return qMetaTypeId<LATorLON>();
}
/*
* is a
*/
template <class LATorLON> bool CEarthAngle<LATorLON>::isA(int metaTypeId) const
{
if (metaTypeId == qMetaTypeId<LATorLON>()) { return true; }
return this->CAngle::isA(metaTypeId);
}
/*
* Compare
*/
template <class LATorLON> int CEarthAngle<LATorLON>::compare(const QVariant &qv) const
template <class LATorLON> int CEarthAngle<LATorLON>::compareImpl(const CValueObject &otherBase) const
{
Q_ASSERT(qv.canConvert<LATorLON>() || qv.canConvert<CAngle>());
Q_ASSERT(qv.isValid() && !qv.isNull());
if (qv.canConvert<LATorLON>())
return this->compare(qv.value<LATorLON>());
else
return this->compare(qv.value<CAngle>());
const auto &other = static_cast<const LATorLON &>(otherBase);
if (*this < other) { return -1; }
else if (*this > other) { return 1; }
else { return 0; }
}
// see here for the reason of thess forward instantiations