Add Feature::unset_field

CHANGES.md

@@ -2,11 +2,14 @@
 
 ## Unreleased
 
-- Added ability to convert between `Buffer<T>` and `ndarray::Array2<T>`. 
-- Implemented `IntoIterator`, `Index` and `IndexMut` for `Buffer<T>`. 
+- Added `Feature::unset_field`
+  - <https://github.com/georust/gdal/pull/503>
+
+- Added ability to convert between `Buffer<T>` and `ndarray::Array2<T>`.
+- Implemented `IntoIterator`, `Index` and `IndexMut` for `Buffer<T>`.
 - **Breaking**: `Buffer<T>::size` is now private and accessed via `Buffer<T>::shape().
-- **Breaking**: `Buffer<T>::data` is now private and accessed via `Buffer<T>::data(). 
-- **Breaking**: Removed `Rasterband::read_as_array`, changed signature of `Rasterband::read_block` to return a `Buffer<T>`. 
+- **Breaking**: `Buffer<T>::data` is now private and accessed via `Buffer<T>::data().
+- **Breaking**: Removed `Rasterband::read_as_array`, changed signature of `Rasterband::read_block` to return a `Buffer<T>`.
 - **Breaking**: `Rasterband::write` and `Rasterband::write_block` now require a `&mut Buffer<T>` to handle possible case of drivers temporarily mutating input buffer.
 
    - <https://github.com/georust/gdal/pull/494>

src/vector/feature.rs

@@ -648,12 +648,28 @@ impl<'a> Feature<'a> {
         }
     }
 
+    /// Clear a field, marking it as null.
+    ///
+    /// See: [`OGRFeature::SetFieldNull`][SetFieldNull]
+    ///
+    /// [SetFieldNull]: https://gdal.org/api/ogrfeature_cpp.html#_CPPv4N10OGRFeature12SetFieldNullEi
     pub fn set_field_null(&self, field_name: &str) -> Result<()> {
         let idx = self.field_idx_from_name(field_name)?;
         unsafe { gdal_sys::OGR_F_SetFieldNull(self.c_feature(), idx) };
         Ok(())
     }
 
+    /// Clear a field, marking it as unset.
+    ///
+    /// See: [`OGRFeature::UnsetField`][UnsetField]
+    ///
+    /// [UnsetField]: https://gdal.org/api/ogrfeature_cpp.html#_CPPv4N10OGRFeature10UnsetFieldEi
+    pub fn unset_field(&self, field_name: &str) -> Result<()> {
+        let idx = self.field_idx_from_name(field_name)?;
+        unsafe { gdal_sys::OGR_F_UnsetField(self.c_feature(), idx) };
+        Ok(())
+    }
+
     pub fn set_geometry(&mut self, geom: Geometry) -> Result<()> {
         let rv = unsafe { gdal_sys::OGR_F_SetGeometry(self.c_feature, geom.c_geometry()) };
         if rv != OGRErr::OGRERR_NONE {
@@ -943,4 +959,15 @@ mod tests {
             }
         }
     }
+
+    #[test]
+    fn test_field_unset() {
+        let ds = Dataset::open(fixture("roads.geojson")).unwrap();
+
+        let mut layer = ds.layers().next().expect("layer");
+        let feature = layer.features().next().expect("feature");
+        for (field_name, _) in feature.fields() {
+            feature.unset_field(&field_name).unwrap();
+        }
+    }
 }