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// Copyright 2014-2015 The GeoRust Developers // // Licensed under the Apache License, Version 2.0 (the "License"); // you may not use this file except in compliance with the License. // You may obtain a copy of the License at // // http://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS IS" BASIS, // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. // See the License for the specific language governing permissions and // limitations under the License. //! # Examples //! //! This crate uses `serde` for serialization. //! To get started, add `geojson` to your `Cargo.toml`: //! //! ```text //! [dependencies] //! geojson= "*" //! ``` //! //! ## Reading //! //! ``` //! use geojson::GeoJson; //! //! let geojson_str = r#" //! { //! "type": "Feature", //! "properties": { //! "name": "Firestone Grill" //! }, //! "geometry": { //! "type": "Point", //! "coordinates": [-120.66029,35.2812] //! } //! } //! "#; //! //! let geojson = geojson_str.parse::<GeoJson>().unwrap(); //! ``` //! //! ## Writing //! //! Writing `geojson` depends on the serialization framework because some structs //! (like `Feature`) use json values for properties. //! //! ``` //! # extern crate geojson; //! extern crate serde_json; //! //! # fn main () { //! use serde_json::{Map, to_value}; //! //! let mut properties = Map::new(); //! properties.insert( //! String::from("name"), //! to_value("Firestone Grill").unwrap(), //! ); //! # } //! ``` //! //! `GeoJson` can then be serialized by calling `to_string`: //! //! ```rust //! # extern crate serde_json; //! # extern crate geojson; //! use geojson::{Feature, GeoJson, Geometry, Value}; //! # fn properties() -> ::serde_json::Map<String, ::serde_json::Value> { //! # let mut properties = ::serde_json::Map::new(); //! # properties.insert( //! # String::from("name"), //! # ::serde_json::Value::String(String::from("Firestone Grill")), //! # ); //! # properties //! # } //! # fn main() { //! # let properties = properties(); //! //! let geometry = Geometry::new( //! Value::Point(vec![-120.66029,35.2812]) //! ); //! //! let geojson = GeoJson::Feature(Feature { //! bbox: None, //! geometry: Some(geometry), //! id: None, //! properties: Some(properties), //! foreign_members: None //! }); //! //! let geojson_string = geojson.to_string(); //! # } //! ``` //! //! ## Parsing //! //! GeoJSON's [spec](https://tools.ietf.org/html/rfc7946) is quite simple, but //! it has several subtleties that must be taken into account when parsing it: //! //! - The `geometry` field of a `Feature` is an `Option` //! - `GeometryCollection`s contain other `Geometry` objects, and can nest. //! //! Here's a minimal example which will parse valid GeoJSON without taking //! ownership of it. //! //! ```rust //! use geojson::{GeoJson, Geometry, Value}; //! //! /// Process GeoJSON geometries //! fn match_geometry(geom: &Geometry) { //! match geom.value { //! Value::Polygon(_) => println!("Matched a Polygon"), //! Value::MultiPolygon(_) => println!("Matched a MultiPolygon"), //! Value::GeometryCollection(ref gc) => { //! println!("Matched a GeometryCollection"); //! // GeometryCollections contain other Geometry types, and can nest //! // we deal with this by recursively processing each geometry //! for geometry in gc { //! match_geometry(geometry) //! } //! } //! // Point, LineString, and their Multi– counterparts //! _ => println!("Matched some other geometry"), //! } //! } //! //! /// Process top-level GeoJSON items //! fn process_geojson(gj: &GeoJson) { //! match *gj { //! GeoJson::FeatureCollection(ref ctn) => for feature in &ctn.features { //! if let Some(ref geom) = feature.geometry { //! match_geometry(geom) //! } //! }, //! GeoJson::Feature(ref feature) => { //! if let Some(ref geom) = feature.geometry { //! match_geometry(geom) //! } //! } //! GeoJson::Geometry(ref geometry) => match_geometry(geometry), //! } //! } //! //! fn main() { //! let geojson_str = r#" //! { //! "type": "GeometryCollection", //! "geometries": [ //! {"type": "Point", "coordinates": [0,1]}, //! {"type": "MultiPoint", "coordinates": [[-1,0],[1,0]]}, //! {"type": "LineString", "coordinates": [[-1,-1],[1,-1]]}, //! {"type": "MultiLineString", "coordinates": [ //! [[-2,-2],[2,-2]], //! [[-3,-3],[3,-3]] //! ]}, //! {"type": "Polygon", "coordinates": [ //! [[-5,-5],[5,-5],[0,5],[-5,-5]], //! [[-4,-4],[4,-4],[0,4],[-4,-4]] //! ]}, //! { "type": "MultiPolygon", "coordinates": [[ //! [[-7,-7],[7,-7],[0,7],[-7,-7]], //! [[-6,-6],[6,-6],[0,6],[-6,-6]] //! ],[ //! [[-9,-9],[9,-9],[0,9],[-9,-9]], //! [[-8,-8],[8,-8],[0,8],[-8,-8]]] //! ]}, //! {"type": "GeometryCollection", "geometries": [ //! {"type": "Polygon", "coordinates": [ //! [[-5.5,-5.5],[5,-5],[0,5],[-5,-5]], //! [[-4,-4],[4,-4],[0,4],[-4.5,-4.5]] //! ]} //! ]} //! ] //! } //! "#; //! let geojson = geojson_str.parse::<GeoJson>().unwrap(); //! process_geojson(&geojson); //! } //! ``` //! //! ## Conversion to Geo objects //! //! The [try_into](conversion/trait.TryInto.html) trait provides *fallible* conversions from GeoJSON Value structs //! to [Geo](https://docs.rs/geo) types, allowing them to be measured or used in calculations. Note that //! this conversion consumes the GeoJSON object, so you will not be able to match //! by reference as in the example above. The [polylabel_cmd](https://github.com/urschrei/polylabel_cmd/blob/master/src/main.rs) crate contains an //! implementation which may be useful if you wish to perform these conversions. extern crate serde; #[macro_use] extern crate serde_json; extern crate geo_types; extern crate num_traits; /// Bounding Boxes /// /// [GeoJSON Format Specification § 5] /// (https://tools.ietf.org/html/rfc7946#section-5) pub type Bbox = Vec<f64>; /// Positions /// /// [GeoJSON Format Specification § 3.1.1] /// (https://tools.ietf.org/html/rfc7946#section-3.1.1) pub type Position = Vec<f64>; pub type PointType = Position; pub type LineStringType = Vec<Position>; pub type PolygonType = Vec<Vec<Position>>; #[macro_use] mod macros; mod util; mod geojson; pub use geojson::GeoJson; mod geometry; pub use geometry::{Geometry, Value}; mod feature; pub use feature::Feature; mod feature_collection; pub use feature_collection::FeatureCollection; /// Convert Geometries into [Geo](https://docs.rs/geo) types pub mod conversion; /// Error when reading a GeoJSON object from a str or Object #[derive(Debug, PartialEq, Eq)] pub enum Error { BboxExpectedArray, BboxExpectedNumericValues, GeoJsonExpectedObject, GeoJsonUnknownType, GeometryUnknownType, MalformedJson, PropertiesExpectedObjectOrNull, FeatureInvalidGeometryValue, // FIXME: make these types more specific ExpectedStringValue, ExpectedProperty, ExpectedF64Value, ExpectedArrayValue, ExpectedObjectValue, } impl std::fmt::Display for Error { fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result { match *self { Error::BboxExpectedArray => // FIXME: inform what type we actually found write!(f, "Encountered non-array type for a 'bbox' object."), Error::BboxExpectedNumericValues => // FIXME: inform what type we actually found write!(f, "Encountered non-numeric value within 'bbox' array."), Error::GeoJsonExpectedObject => // FIXME: inform what type we actually found write!(f, "Encountered non-object type for GeoJSON."), Error::GeoJsonUnknownType => // FIXME: inform what type we actually found write!(f, "Encountered unknown GeoJSON object type."), Error::GeometryUnknownType => write!(f, "Encountered unknown 'geometry' object type."), Error::MalformedJson => // FIXME: can we report specific serialization error? write!(f, "Encountered malformed JSON."), Error::PropertiesExpectedObjectOrNull => // FIXME: inform what type we actually found write!(f, "Encountered neither object type nor null type for \ 'properties' object."), Error::FeatureInvalidGeometryValue => // FIXME: inform what type we actually found write!(f, "Encountered neither object type nor null type for \ 'geometry' field on 'feature' object."), Error::ExpectedStringValue => write!(f, "Expected a string value."), Error::ExpectedProperty => write!(f, "Expected a GeoJSON 'property'."), Error::ExpectedF64Value => write!(f, "Expected a floating-point value."), Error::ExpectedArrayValue => write!(f, "Expected an array."), Error::ExpectedObjectValue => write!(f, "Expected an object."), } } } impl std::error::Error for Error { fn description(&self) -> &str { match *self { Error::BboxExpectedArray => "non-array 'bbox' type", Error::BboxExpectedNumericValues => "non-numeric 'bbox' array", Error::GeoJsonExpectedObject => "non-object GeoJSON type", Error::GeoJsonUnknownType => "unknown GeoJSON object type", Error::GeometryUnknownType => "unknown 'geometry' object type", Error::MalformedJson => "malformed JSON", Error::PropertiesExpectedObjectOrNull => { "neither object type nor null type for properties' object." } Error::FeatureInvalidGeometryValue => { "neither object type nor null type for 'geometry' field on 'feature' object." } Error::ExpectedStringValue => "expected a string value", Error::ExpectedProperty => "expected a GeoJSON 'property'", Error::ExpectedF64Value => "expected a floating-point value", Error::ExpectedArrayValue => "expected an array", Error::ExpectedObjectValue => "expected an object", } } } mod json { pub use serde::{Deserialize, Deserializer, Serialize, Serializer}; pub use serde_json::{Map, Value as JsonValue}; pub type JsonObject = Map<String, JsonValue>; } trait FromObject: Sized { fn from_object(object: json::JsonObject) -> Result<Self, Error>; }