C++ keyword operator on "this" pointer

Question

Struggling to understand this syntax that I've run across in open source code:

/// cast *this into an gpstk::RinexNavData.
/// @throw if the record is invalid or not an ephemeris (isNav()==false)
operator RinexNavData() throw(gpstk::Exception);

/// cast *this into a gpstk::RinexObsData
/// @throw if the record is invalid or not an observation (isObs()==false)
operator RinexObsData() throw(gpstk::Exception);

If I interpret the comment correctly, it is changing the type of the object via the "this" pointer. But this appears to be done via an operator? Can't hit on a good web search that involves the keyword "this". Looking for a reference or explanation on how this use of "operator" works. Web search of C++ operator doesn't lead to anything like this, that I've found so far.

this is a quite exhaustive q&a on operator overloading: https://stackoverflow.com/questions/4421706/what-are-the-basic-rules-and-idioms-for-operator-overloading you will also find a section on conversion operators — 463035818_is_not_an_ai, Feb 27 '18 at 18:22
@freim: I thought your answer was good and presented a useful example - would you consider undeleting it? — Lightness Races in Orbit, Feb 27 '18 at 19:00

score 3 · Accepted Answer · answered Feb 27 '18 at 18:09

3

Don't overthink the use of this here; *this just means "the current object", so the programmer is using a shorthand to describe what the operator does.

Indeed, like any conversion operator, it takes the current object and provides a means to convert it to a different type.

answered Feb 27 '18 at 18:09

Lightness Races in Orbit

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Minor nitpick: `this` is not converted. A new object is created (from `this`) via the cast operator, but I would expect `this` to remain unchanged. That in turn begets the question why the operator is not marked `const`, but that's a new discussion. – Ulrich Eckhardt Feb 28 '18 at 12:19
@UlrichEckhardt: `this` is certainly not converted. In C++ parlance, though, `*this` is - making a copy is part of the conversion procedure (it happens every time you make a value cast!). Indeed you cannot transform an object to a different type in-place. – Lightness Races in Orbit Feb 28 '18 at 12:23

C++ keyword operator on "this" pointer

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