Allocating memory to a pointer of a class

QGeoRoutingManager: http://apidocs.meego.com/1.0/qtmobility/qgeoroutingmanager-members.html

This class doesn't have a constructor. I have forgotten the way to allocate memory to its pointer.

I did:

QGeoRoutingManager *a = new QGeoRoutingManager ();

This lands in the error:

calculateRoute.cpp:16: error: no matching function for call to ‘QtMobility::QGeoRoutingManager::QGeoRoutingManager()’
../../../../tarBalls/q开发者_JS百科t-mobility-opensource-src-1.2.0/install/include/QtLocation/qgeoroutingmanager.h:91: note: candidates are: QtMobility::QGeoRoutingManager::QGeoRoutingManager(const QtMobility::QGeoRoutingManager&)

What should I pass in there, as per the error message "const QtMobility::QGeoRoutingManager&"

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This is a singleton class, you can access it like this:

QGeoServiceProvider::routingManager().

Check the docs

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If the class doesn't have a public (default) constructor, you can't (directly) create a new instance of it, neither on the stack nor on the free store (heap). You could only possibly create a copy of an existing one, but the docs don't show a copy ctor available.

Look through the documentation if there is a factory function / class to create instances of that class.

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The class QGeoRoutingManager does not have default constructor. The default constructor is one which doesn't take any argument. If it takes, then they're optional (with default value).

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The class does have a constructor; all classes have a constructor. The class apparently doesn't have a default constructor. You don't show us the class, so we have to guess, but from the error message, the class does have a copy constructor. Did you provide it? As soon as there are any user defined constructors, the compiler will not generate a default constructor; you have to provide one of those too.

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I think you need QGeoRoutingManager * QGeoServiceProvider::routingManager () const

Check here: https://doc-snapshots.qt.io/qt-mobility/qgeoserviceprovider.html