c++ - let function return template type -


i had following function

slabwallconnectionevent* createobservedevent(slabwallconnectionevent::data* peventdata) {     assert(peventdata != nullptr);     return slabwallconnectionevent::create(peventdata->m_wall, peventdata->m_slab); }

then able make more general template template specification.

.h file

template <class observedeventtype, class observedeventdatatype> void createobservedevent(observedeventtype*& pevent,observedeventdatatype* peventdata);

.cpp file

template<> void createobservedevent<slabwallconnectionevent, slabwallconnectionevent::data>                 (slabwallconnectionevent*& pevent, slabwallconnectionevent::data* peventdata) {     assert(peventdata != nullptr);     pevent = slabwallconnectionevent::create(peventdata->m_wall, peventdata->m_slab); }

this works me not pleased reference raw pointer. possible change this:

.h file

template <class observedeventtype, class observedeventdatatype> observedeventtype* createobservedevent(observedeventdatatype* peventdata);

.cpp file

template<> slabwallconnectionevent* createobservedevent<slabwallconnectionevent, slabwallconnectionevent::data>                 (bim_ui::slabwallconnectionevent::data* peventdata) {     assert(peventdata != nullptr);     return bim_ui::slabwallconnectionevent::create(peventdata->m_wall, peventdata->m_slab); }

when try use following error:

error   1   error c2783: 'observedeventtype  *createobservedevent(observedeventdatatype *)' : not deduce template  argument 'observedeventtype'

edit
use function in template function

template <class observedeventtype> void cmdbimdrag::observeconnectionevent(observedeventdata* pobservedevent){     ...     if (pcurrentevent == nullptr)         createobservedevent(pcurrentevent, peventdata);     ... }

and function gets called this

observeconnectionevent<slabwallconnectionevent>((*pobservedeventdata).get());

edit2

jonas' answers first part works specifying template type enough:

createobservedevent<slabwallconnectionevent>(peventdata);

however using auto not seem warrant removal of return type spefication:

.h file

template <class observedeventtype, class observedeventdatatype> auto createobservedevent(observedeventdatatype* peventdata) -> observedeventtype*;

.cpp file

template<> auto createobservedevent<slabwallconnectionevent, slabwallconnectionevent::data>     (slabwallconnectionevent::data* peventdata) -> slabwallconnectionevent* {     assert(peventdata != nullptr);     return slabwallconnectionevent::create(peventdata->m_wall, peventdata->m_slab); }

this code compiles template specification calling:

createobservedevent(peventdata);

still gives first error not being able deduce type.

you have specific return type:

createobservedevent<slabwallconnectionevent>(peventdata);

here example, using simpler types.

alternatively, use auto return type , not include template parameter return type. online example here.


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