Add a flexible QgsInterval constructor for creating from years/months/days/etc

python/core/auto_generated/qgsinterval.sip.in

@@ -47,6 +47,22 @@ Constructor for QgsInterval.
     QgsInterval( double duration, QgsUnitTypes::TemporalUnit unit );
 %Docstring
 Constructor for QgsInterval, using the specified ``duration`` and ``units``.
+%End
+
+    QgsInterval( double years, double months, double weeks, double days, double hours, double minutes, double seconds );
+%Docstring
+Constructor for QgsInterval, using the specified ``years``, ``months``,
+``weeks``, ``days``, ``hours``, ``minutes`` and ``seconds``.
+
+.. note::
+
+   Month units assumes a 30 day month length.
+
+.. note::
+
+   Year units assumes a 365.25 day year length.
+
+.. versionadded:: 3.14
 %End
 
     double years() const;

src/core/qgsinterval.cpp

@@ -40,6 +40,19 @@ QgsInterval::QgsInterval( double duration, QgsUnitTypes::TemporalUnit unit )
 
 }
 
+QgsInterval::QgsInterval( double years, double months, double weeks, double days, double hours, double minutes, double seconds )
+  : mSeconds( years * QgsUnitTypes::fromUnitToUnitFactor( QgsUnitTypes::TemporalYears, QgsUnitTypes::TemporalSeconds )
+              + months * QgsUnitTypes::fromUnitToUnitFactor( QgsUnitTypes::TemporalMonths, QgsUnitTypes::TemporalSeconds )
+              + weeks * QgsUnitTypes::fromUnitToUnitFactor( QgsUnitTypes::TemporalWeeks, QgsUnitTypes::TemporalSeconds )
+              + days * QgsUnitTypes::fromUnitToUnitFactor( QgsUnitTypes::TemporalDays, QgsUnitTypes::TemporalSeconds )
+              + hours * QgsUnitTypes::fromUnitToUnitFactor( QgsUnitTypes::TemporalHours, QgsUnitTypes::TemporalSeconds )
+              + minutes * QgsUnitTypes::fromUnitToUnitFactor( QgsUnitTypes::TemporalMinutes, QgsUnitTypes::TemporalSeconds )
+              + seconds )
+  , mValid( true )
+{
+
+}
+
 bool QgsInterval::operator==( QgsInterval other ) const
 {
   if ( !mValid && !other.mValid )

src/core/qgsinterval.h

@@ -72,6 +72,17 @@ class CORE_EXPORT QgsInterval
      */
     QgsInterval( double duration, QgsUnitTypes::TemporalUnit unit );
 
+    /**
+     * Constructor for QgsInterval, using the specified \a years, \a months,
+     * \a weeks, \a days, \a hours, \a minutes and \a seconds.
+     *
+     * \note Month units assumes a 30 day month length.
+     * \note Year units assumes a 365.25 day year length.
+     *
+     * \since QGIS 3.14
+     */
+    QgsInterval( double years, double months, double weeks, double days, double hours, double minutes, double seconds );
+
     /**
      * Returns the interval duration in years (based on an average year length)
      * \see setYears()

tests/src/python/test_qgsinterval.py

@@ -166,6 +166,24 @@ class TestQgsInterval(unittest.TestCase):
         i = QgsInterval.fromString('bad')
         self.assertFalse(i.isValid())
 
+    def testFromUnits(self):
+        i = QgsInterval(2, 0, 0, 0, 0, 0, 0)
+        self.assertEqual(i.seconds(), 63115200.0)
+        i = QgsInterval(0, 2, 0, 0, 0, 0, 0)
+        self.assertEqual(i.seconds(), 5184000.0)
+        i = QgsInterval(0, 0, 2, 0, 0, 0, 0)
+        self.assertEqual(i.seconds(), 1209600.0)
+        i = QgsInterval(0, 0, 0, 2, 0, 0, 0)
+        self.assertEqual(i.seconds(), 172800.0)
+        i = QgsInterval(0, 0, 0, 0, 2, 0, 0)
+        self.assertEqual(i.seconds(), 7200.0)
+        i = QgsInterval(0, 0, 0, 0, 0, 2, 0)
+        self.assertEqual(i.seconds(), 120.0)
+        i = QgsInterval(0, 0, 0, 0, 0, 0, 2)
+        self.assertEqual(i.seconds(), 2)
+        i = QgsInterval(1.5, 2.5, 3.5, 4.5, 5.5, 6.5, 2)
+        self.assertEqual(i.seconds(), 56342192.0)
+
 
 if __name__ == '__main__':
     unittest.main()