How to output a GeoJSONFeatureCollection?

[mklnz]

Edit: Now I found out this is due to a conflict between Rail's ActiveSupport to_json and the json gem. Usage outside Rails environment works as intended. How to get around this?

I'm not sure if I'm using this functionality correctly or not, but I'm having trouble outputting a valid GeoJSON collection.

Example:
GeoJSONFeature.new(point1).to_json

Output:

{  
   "type":"Feature",
   "geometry":{  
      "type":"Point",
      "coordinates":[  
         121.4412656998513,
         31.2108137285587
      ]
   },
   "properties":{  
   }
}

But when a GeoJSONFeature is inside an array, it skips over its own GeoJSONFeature#to_json method (double checked with byebug) and is missing the "type": "Feature" attribute.

Example:
[GeoJSONFeature.new(point1)].to_json

Output:

[  
   {  
      "geometry":{  
         "type":"Point",
         "coordinates":[  
            121.4412656998513,
            31.2108137285587
         ]
      },
      "properties":{  
      },
      "id":null
   }
]

Finally putting it together with a FeatureCollection:

    features = [
      GeoJSONFeature.new(start_point),
      GeoJSONFeature.new(end_point)
    ]
    GeoJSONFeatureCollection.new(features)

Output (not valid GeoJSON):

{  
   "type":"FeatureCollection",
   "features":[  
      {  
         "geometry":{  
            "type":"Point",
            "coordinates":[  
               121.4412656998513,
               31.2108137285587
            ]
         },
         "properties":{  
         },
         "id":null
      },
      {  
         "geometry":{  
            "type":"Point",
            "coordinates":[  
               121.4569708797648,
               31.219778491221284
            ]
         },
         "properties":{  
         },
         "id":null
      }
   ]
}

[nofxx]

Out of coincidence: working on this json thing.
It's too awkward now. It should be anything.to_geojson and we're good.
Gonna let you know.