mpiannucci / FeatureShapes

Create SwiftUI Shapes from GeoJSON Features

FeatureShapes

Create SwiftUI Shapes from GeoJSON Features. Inspired by d3-path and d3-geo.

Installation

This package is available via Swift Package Manager, add its git url to your project to get started.

Usage

Given a GeoJSON Feature:

let line = Feature(
    geometry: .lineString(try! LineString(coordinates: [
        Position(longitude: 10, latitude: 10),
        Position(longitude: 20, latitude: 10),
        Position(longitude: 20, latitude: 30)
    ])),
    properties: [:]
)

It can be rendered using a FeatureShape:

        FeatureShape(feature: line, projection: IdentityProjection())
            .stroke(lineWidth: 2.0)
            .foregroundColor(.red)

Projections

SwiftUI Shapes are drawn from Paths. To draw paths, you given instructions based on CGPoint locations inside of a given CGRect. The GeoJSON package assumes that all positions are latitude and longitude pairs but that may not be the case or the data may be in a bespoke projection system. To stay low level, the Paths created use a projection protocol map from GeoJSON location to Path location.

Currently there is a single projection included with this package, the IdentityProjection. This projection simply converts the GeoJSON Position object to a CGPoint.

To create a custom projection, simply create an object the implements the Projection protocol, mapping the GeoJSON Position objects in any way desired.