How to group an array of hash by its value which has key-value pair in Ruby (Rails)?-CodePudding

So I have following array of hash:

my_array = [
  {
    "date" => "2022-12-01",
    "pic" => "Jason",
    "guard" => "Steven",
    "front_desk" => "Emily"
  },
  {
    "date" => "2022-12-02",
    "pic" => "Gilbert",
    "guard" => "Johnny",
    "front_desk" => "Bella"
  },
  {
    "date" => "2022-12-03",
    "pic" => "Steven",
    "guard" => "Gilbert",
    "front_desk" => "Esmeralda"
  }
]

My question is how do I change the structure of my array (grouping) by date in Ruby (Rails 7). Or in other word, I want to change my array into something like this:

my_array = [
  {
    "2022-12-01" => {
        "pic" => "Jason",
        "guard" => "Steven",
        "front_desk" => "Emily"
    {
  },
  {
    "2022-12-02" => {
      "pic" => "Gilbert",
      "guard" => "Johnny",
      "front_desk" => "Bella"
    }
  },
  {
    "2022-12-03" => {
      "pic" => "Steven",
      "guard" => "Gilbert",
      "front_desk" => "Esmeralda"
    }
  }
]

Anyway, thanks in advance for the answer

I have tried using group_by method to group by its date, but it doesn't give the output I wanted

I've tried this method:

my_array.group_by { |element| element["date"] }.values

CodePudding user response：

If you simply want a 1:1 mapping of your input objects to an output object of a new shape, then you just need to use Array#map:

my_array.map {|entry| {entry["date"] => entry.except("date")} }

(Hash#except comes from ActiveSupport, and is not standard Ruby, but since you're in Rails it should work just fine).

CodePudding user response：

Both solutions assume the key "date" will be unique. If we cannot make this assumption safely, then each date should be mapped to an array of hashes.

my_array.each_with_object({}) do |x, hsh|
  date = x["date"]
  hsh[date] ||= []
  hsh[date] << x.except("date")
end

Result:

{
  "2022-12-01" => [
    {"pic"=>"Jason", "guard"=>"Steven", "front_desk"=>"Emily"}
  ], 
  "2022-12-02" => [
    {"pic"=>"Gilbert", "guard"=>"Johnny", "front_desk"=>"Bella"}
  ], 
  "2022-12-03" => [
    {"pic"=>"Steven", "guard"=>"Gilbert", "front_desk"=>"Esmeralda"}
  ]
}

Or you may like:

my_array
  .sort_by { |x| x["date"] }
  .group_by { |x| x["date"] }
  .transform_values { |x| x.except("date") }

CodePudding user response：

Try this

result = my_array.each_with_object({}) do |element, hash|
 hash[element["date"]] = element.except("date")
end

puts result

I hope this helps! :)