example_test.go

package geojson_test

import (
	"encoding/json"
	"fmt"
	"log"

	"github.com/paulmach/orb"
	"github.com/paulmach/orb/geojson"
	"github.com/paulmach/orb/quadtree"
)

func ExampleFeature_Point() {
	f := geojson.NewFeature(orb.Point{1, 1})
	f.Properties["key"] = "value"

	qt := quadtree.New(f.Geometry.Bound().Pad(1))
	err := qt.Add(f) // add the feature to a quadtree
	if err != nil {
		log.Fatalf("unexpected error: %v", err)
	}

	// type assert the feature back into a Feature from
	// the orb.Pointer interface.
	feature := qt.Find(orb.Point{0, 0}).(*geojson.Feature)
	fmt.Printf("key=%s", feature.Properties["key"])

	// Output:
	// key=value
}

func ExampleFeatureCollection_foreignMembers() {
	rawJSON := []byte(`
	  { "type": "FeatureCollection",
	    "features": [
	      { "type": "Feature",
	        "geometry": {"type": "Point", "coordinates": [102.0, 0.5]},
	        "properties": {"prop0": "value0"}
	      }
	    ],
	    "title": "Title as Foreign Member"
	  }`)

	fc := geojson.NewFeatureCollection()
	err := json.Unmarshal(rawJSON, &fc)
	if err != nil {
		log.Fatalf("invalid json: %v", err)
	}

	fmt.Println(fc.Features[0].Geometry)
	fmt.Println(fc.ExtraMembers["title"])

	data, _ := json.Marshal(fc)
	fmt.Println(string(data))

	// Output:
	// [102 0.5]
	// Title as Foreign Member
	// {"features":[{"type":"Feature","geometry":{"type":"Point","coordinates":[102,0.5]},"properties":{"prop0":"value0"}}],"title":"Title as Foreign Member","type":"FeatureCollection"}
}

// MyFeatureCollection is a depricated/no longer supported way to extract
// foreign/extra members from a feature collection. Now an UnmarshalJSON
// method, like below, is required for it to work.
type MyFeatureCollection struct {
	geojson.FeatureCollection
	Title string `json:"title"`
}

// UnmarshalJSON implemented as below is now required for the extra members
// to be decoded directly into the type.
func (fc *MyFeatureCollection) UnmarshalJSON(data []byte) error {
	err := json.Unmarshal(data, &fc.FeatureCollection)
	if err != nil {
		return err
	}

	fc.Title = fc.ExtraMembers.MustString("title", "")
	return nil
}

func ExampleFeatureCollection_foreignMembersCustom() {
	// Note: this approach to handling foreign/extra members requires
	// implementing an `UnmarshalJSON` method on the new type.
	// See MyFeatureCollection type and its UnmarshalJSON function above.

	rawJSON := []byte(`
	  { "type": "FeatureCollection",
	    "features": [
	      { "type": "Feature",
	        "geometry": {"type": "Point", "coordinates": [102.0, 0.5]},
	        "properties": {"prop0": "value0"}
	      }
	    ],
	    "title": "Title as Foreign Member"
	  }`)

	fc := &MyFeatureCollection{}
	err := json.Unmarshal(rawJSON, &fc)
	if err != nil {
		log.Fatalf("invalid json: %v", err)
	}

	fmt.Println(fc.FeatureCollection.Features[0].Geometry)
	fmt.Println(fc.Features[0].Geometry)
	fmt.Println(fc.Title)
	// Output:
	// [102 0.5]
	// [102 0.5]
	// Title as Foreign Member
}

func ExampleUnmarshalFeatureCollection() {
	rawJSON := []byte(`
	  { "type": "FeatureCollection",
	    "features": [
	      { "type": "Feature",
	        "geometry": {"type": "Point", "coordinates": [102.0, 0.5]},
	        "properties": {"prop0": "value0"}
	      }
	    ]
	  }`)

	fc, _ := geojson.UnmarshalFeatureCollection(rawJSON)

	// Geometry will be unmarshalled into the correct geo.Geometry type.
	point := fc.Features[0].Geometry.(orb.Point)
	fmt.Println(point)

	// Output:
	// [102 0.5]
}

func Example_unmarshal() {
	rawJSON := []byte(`
	  { "type": "FeatureCollection",
	    "features": [
	      { "type": "Feature",
	        "geometry": {"type": "Point", "coordinates": [102.0, 0.5]},
	        "properties": {"prop0": "value0"}
	      }
	    ]
	  }`)

	fc := geojson.NewFeatureCollection()
	err := json.Unmarshal(rawJSON, &fc)
	if err != nil {
		log.Fatalf("invalid json: %v", err)
	}

	// Geometry will be unmarshalled into the correct geo.Geometry type.
	point := fc.Features[0].Geometry.(orb.Point)
	fmt.Println(point)

	// Output:
	// [102 0.5]
}

func ExampleFeatureCollection_MarshalJSON() {
	fc := geojson.NewFeatureCollection()
	fc.Append(geojson.NewFeature(orb.Point{1, 2}))

	_, err := fc.MarshalJSON()
	if err != nil {
		log.Fatalf("marshal error: %v", err)
	}

	// standard lib encoding/json package will also work
	data, err := json.MarshalIndent(fc, "", " ")
	if err != nil {
		log.Fatalf("marshal error: %v", err)
	}

	fmt.Println(string(data))

	// Output:
	// {
	//  "features": [
	//   {
	//    "type": "Feature",
	//    "geometry": {
	//     "type": "Point",
	//     "coordinates": [
	//      1,
	//      2
	//     ]
	//    },
	//    "properties": null
	//   }
	//  ],
	//  "type": "FeatureCollection"
	// }
}