From f567c602ffb63578a568b4abda195e356e6c3460 Mon Sep 17 00:00:00 2001
From: Anton Maminov <anton.linux@gmail.com>
Date: Sun, 29 Mar 2020 19:10:28 +0300
Subject: [PATCH] adds #area method for all GeoJSON objects

---
 README.md                 | 15 ++++++++++++++-
 spec/geojson_area_spec.cr | 11 +++++++++++
 src/geojson/object.cr     |  7 +++++++
 src/geojson_area.cr       |  1 +
 4 files changed, 33 insertions(+), 1 deletion(-)
 create mode 100644 src/geojson/object.cr

diff --git a/README.md b/README.md
index dc4af3d..efcc4ec 100644
--- a/README.md
+++ b/README.md
@@ -23,7 +23,20 @@ Calculate the area inside of any [GeoJSON](https://github.com/geocrystal/geojson
 require "geojson_area"
 ```
 
-`GeoJSON::Area.area()` accept any `GeoJSON` object, and returns contained area as square meters.
+This adds `area` method for all `GeoJSON` objects:
+
+```crystal
+polygon = GeoJSON::Polygon.new([
+  [[-10.0, -10.0], [10.0, -10.0], [10.0, 10.0], [-10.0,-10.0]],
+  [[-1.0, -2.0], [3.0, -2.0], [3.0, 2.0], [-1.0,-2.0]]
+])
+
+polygon.area
+# => 2366726096087.807
+```
+
+Also you can use `GeoJSON::Area.area()` directly.
+This method accept any `GeoJSON` object, and returns contained area as square meters.
 
 ```crystal
 polygon = GeoJSON::Polygon.new([
diff --git a/spec/geojson_area_spec.cr b/spec/geojson_area_spec.cr
index 6ef0faf..3782026 100644
--- a/spec/geojson_area_spec.cr
+++ b/spec/geojson_area_spec.cr
@@ -58,4 +58,15 @@ describe GeoJSON::Area do
     area = GeoJSON::Area.area(polygon)
     area.should eq(2366726096087.807)
   end
+
+  describe GeoJSON::Object do
+    it "#area" do
+      polygon = GeoJSON::Polygon.new([
+        [[-10.0, -10.0], [10.0, -10.0], [10.0, 10.0], [-10.0, -10.0]],
+        [[-1.0, -2.0], [3.0, -2.0], [3.0, 2.0], [-1.0, -2.0]],
+      ])
+
+      polygon.area.should eq(2366726096087.807)
+    end
+  end
 end
diff --git a/src/geojson/object.cr b/src/geojson/object.cr
new file mode 100644
index 0000000..87ada7a
--- /dev/null
+++ b/src/geojson/object.cr
@@ -0,0 +1,7 @@
+module GeoJSON
+  class Object
+    def area : Float64
+      GeoJSON::Area.area(self)
+    end
+  end
+end
diff --git a/src/geojson_area.cr b/src/geojson_area.cr
index 9098102..f28fc3c 100644
--- a/src/geojson_area.cr
+++ b/src/geojson_area.cr
@@ -1,5 +1,6 @@
 require "geojson"
 require "./geojson/area"
+require "./geojson/object"
 
 module GeoJSON::Area
   VERSION = {{ `shards version #{__DIR__}`.chomp.stringify }}