crystal_json_builder

require "json"
d = {1 => {"a" => 1, "b" => 2}, 2 => {"a" => 3, "b" => 4}}
class AnyClass
    property color
    property size
    def initialize(@color : String, @size : Int32)
    end

    def to_json (jb : JSON::Builder)
        jb.object do
            jb.field "color", self.color
            jb.field "size", self.size
        end
    end
end

s = JSON.build do |j|
    j.object do
        d.each do |k,v|
            j.field k do
                j.object do
                    j.field "a", v["a"]
                    j.field "b", v["b"]
                end
            end
        end
    end
end

puts "manually: " + s

inst = AnyClass.new("red", 42)

h = {"my_object" => inst}

puts "to_json: " + h.to_json