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qgis-rs

features

qgis_render::features

How you ask a layer for data. Requests are pushed down to the provider, so filtering, bounding boxes, and column selection avoid reading rows you will throw away.

use qgis_render::features::*;

FeatureRequest

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 layer.features_with(request) {
    // ...
}
MethodDescription
.filter(Filter)Attribute predicate, pushed to the provider where possible.
.bounding_box(Extent)Spatial filter on the layer index.
.intersects(&Geometry)Spatial filter against an arbitrary geometry.
.select([...])Only these fields; include "geometry" to keep the geometry.
.select_all()Every field, the default.
.limit(usize)Stop after N features.
.offset(usize)Skip the first N features.
.no_geometry()Skip geometry entirely — much faster for statistics.
.order_by(&str, bool)Sort by a field, ascending or descending.

Filter

Filter::eq("type", "residential")
Filter::gt("height", 50)
Filter::lt("height", 100)
Filter::gte("height", 50)
Filter::lte("height", 100)
Filter::ne("type", "industrial")
Filter::is_null("name")
Filter::in_list("type", ["a", "b"])
Filter::and(f1, f2)
Filter::or(f1, f2)
Filter::not(f)
Filter::expr("\"height\" > 50 AND \"type\" = 'residential'")

Filter::expr takes a full QGIS expression — see expr.

Iteration

FeatureIterator is lazy: features are fetched in provider-sized batches as you consume them, and nothing is buffered beyond the current batch.

// Counts without touching attributes
let total = layer.count_with(FeatureRequest::new())?;


// Statistics without geometry
let mut tallest = 0.0;
for feature in layer.features_with(FeatureRequest::new().no_geometry()) {
    tallest = tallest.max(feature.get::<f64>("height")?);
}

See also