rubyでハッシュの配列を指定したキーでマージするメソッドがあると便利

DB分割等でjoinできない時など、ruby側でDBのデータをマージしないといけない時によく使います

array.rb

class Array
    def merge_by_index(other,index1='id',index2=nil)
        index2 = index1 if index2.nil?
        merge_hash = {}
        self.map {|data| merge_hash[data[index1]] = data}
        other.each do |data|
            key = data[index2]
            data[index1] = key if index1 != index2
            data.delete(index2) if index1 != index2
            merge_hash[key] = (merge_hash[key] == nil) ? data : merge_hash[key].merge(data) 
        end
        return merge_hash.values 
    end 
end

indexをキーに配列をマージする

a = [
    {'id' => 1,'val' => 1},
    {'id' => 2,'val' => 1}
]

b = [
    {'id' => 2,'val' => 2},
    {'id' => 3,'val' => 2}
]

p a.merge_by_index(b)
#=> [{"id"=>1, "val"=>1}, {"id"=>2, "val"=>2}, {"id"=>3, "val"=>2}]

joinする

a = [
    {'id' => 1,'val' => 1}
]
b = [
    {'id' => 1,'name' => 'hoge'}
]

p a.merge_by_index(b)
#=> [{"id"=>1, "val"=>1, "name"=>"hoge"}]

indexを指定する(デフォルトは'id')

a = [
    {'user_id' => 1,'val' => 1}
]
b = [
    {'user_id' => 1,'score' => 100}
]

p a.merge_by_index(b,'user_id')
#=> [{"user_id"=>1, "val"=>1, "score"=>100}]

キーの名前が違う配列同士でマージする

a = [
    {'id' => 1,'val' => 1}
]
b = [
    {'user_id' => 1,'score' => 100}
]

p a.merge_by_index(b,'id','user_id')
#=> [{"id"=>1, "val"=>1, "score"=>100}]