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qgis-rs

Feature

Feature

use qgis_render::Feature;

One row of a vector layer: an id, a set of attributes, and usually a geometry. Features come from a VectorLayer iterator, so they are cheap to stream and never require the whole layer in memory.

Reading a feature

for feature in buildings.features() {
    let id = feature.id();
    let name: String = feature.get("name")?;
    let height: f64 = feature.get("height")?;
    let geom = feature.geometry();


    println!("{id}: {name} ({height} m) {:?}", geom.geometry_type());
}
MethodReturnsDescription
id()i64Feature id.
get(name)Result<Value, QgisError>Attribute by field name, converted to the target type.
try_get(name)Option<Result<Value, QgisError>>None when the field does not exist.
attributes()&[Value]Raw attribute values in field order.
geometry()Option<&Geometry>None for tables without geometry.
is_valid()boolWhether the feature passed provider validation.

Filtered iteration

Fetching only what you need is the single biggest performance win with large layers — the filter is pushed down to the provider.

use qgis_render::features::{FeatureRequest, Filter};


let request = FeatureRequest::new()
    .filter(Filter::gt("height", 50))
    .bounding_box(Extent::new(14.0, 50.0, 15.0, 51.0))
    .select(["name", "height", "geometry"])
    .limit(1000);


for feature in buildings.features_with(request) {
    println!("{}: {}m", feature.get::<String>("name")?, feature.get::<f64>("height")?);
}

Single features and counts

let feature = buildings.feature(42)?;


let tall = buildings.count_with(
    FeatureRequest::new().filter(Filter::gt("height", 50))
)?;

Spatial queries

let request = FeatureRequest::new()
    .intersects(&some_polygon)
    .select_all();


for feature in buildings.features_with(request) {
    // ...
}

See also