Question

我想加入两个哈希值，比如数据库表，并将它们合并到一个哈希中。我有两组哈希，如下所示：

哈希1：

classrooms = [{"id"=>4, "title"=>"Class A"}]

哈希2：

teacher_lessons = [{"program_day"=>1, "bell"=>1, "lesson_id"=>1, "classroom_id"=>4},
 {"program_day"=>1, "bell"=>2, "lesson_id"=>3, "classroom_id"=>4},
 {"program_day"=>2, "bell"=>1, "lesson_id"=>4, "classroom_id"=>4}]

预期：

[{"program_day"=>1, "bell"=>1, "lesson_id"=>1, "classroom_id"=>4, "classroom_title"=> "Class A"},
 {"program_day"=>1, "bell"=>2, "lesson_id"=>3, "classroom_id"=>4, "classroom_title"=> "Class A"},
 {"program_day"=>2, "bell"=>1, "lesson_id"=>4, "classroom_id"=>4, "classroom_title"=> "Class A"}]

Answer 1

假设你有很多教室，我会先改变教室数据：

classrooms = [{"id" => 4, "title" => "Class A"}, 
              {"id" => 5, "title" => "Class B"}]
title_by_id = classrooms.map(&:values).to_h
#=> {4=>"Class A", 5=>"Class B"}

然后根据“classroom_id”键简单地修改每个哈希：

teacher_lessons.each {|hash| hash["title"] = title_by_id[hash["classroom_id"]]}
#=>[{"program_day"=>1,"bell"=>1,"lesson_id"=>1,"classroom_id"=>4,"title"=>"Class A"},
#   {"program_day"=>1,"bell"=>2,"lesson_id"=>3,"classroom_id"=>4,"title"=>"Class A"},
#   {"program_day"=>2,"bell"=>1,"lesson_id"=>4,"classroom_id"=>4,"title"=>"Class A"}]

如果您不想修改源对象，请使用map + merge：

teacher_lessons.map {|h| h.merge("title" => title_by_id[h["classroom_id"]])}

合并哈希数组

1 个答案: