Hashの抽出

params = {:aaa => "a", :bbb => "b", :ccc => "c", :ddd => "d"}

から

=> {:aaa=>"a", :bbb=>"b", :ccc=>"c"}

を生成する。

sample1.rb

params = {:aaa => "a", :bbb => "b", :ccc => "c", :ddd => "d"}
#1.
result_1 = {:aaa => params[:aaa], :bbb => params[:bbb], :ccc => params[:ccc]} 
#2.
result_2 = {}
[:aaa, :bbb, :ccc].each{|k| result_2[k] = params[k]}
#3.
result_3 = [[:aaa, :bbb, :ccc], params.values_at(:aaa, :bbb, :ccc)].transpose.to_h
#4. Rails拡張
result_4 = params.slice(:aaa, :bbb, :ccc)

p result_1
p result_2
p result_3
p result_4

result1.

{:aaa=>"a", :bbb=>"b", :ccc=>"c"}
{:aaa=>"a", :bbb=>"b", :ccc=>"c"}
{:aaa=>"a", :bbb=>"b", :ccc=>"c"}
{:aaa=>"a", :bbb=>"b", :ccc=>"c"}

4.のみキーが存在しない際の動きが異なる。

sample2.rb

params = {:aaa => "a", :bbb => "b", :ccc => "c", :ddd => "d"}
#1.
result_1 = {:aaa => params[:aaa], :bbb => params[:bbb], :hoge => params[:hoge]}.
#2.
result_2 = {}
[:aaa, :bbb, :hoge].each{|k| result_2[k] = params[k]}
#3.
result_3 = [[:aaa, :bbb, :hoge], params.values_at(:aaa, :bbb, :hoge)].transpose.to_h
#4. Rails拡張
result_4 = params.slice(:aaa, :bbb, :hoge)

p result_1
p result_2
p result_3
p result_4

result2.

{:aaa=>"a", :bbb=>"b", :hoge=>nil}
{:aaa=>"a", :bbb=>"b", :hoge=>nil}
{:aaa=>"a", :bbb=>"b", :hoge=>nil}
{:aaa=>"a", :bbb=>"b"}

100000回実行時の処理速度

No.	time(s)
1	0.05948762223124504
2	0.08977324888110161
3	0.13127699121832848
4	0.19742310792207718