how to convert a hash value returned from a date_select in rails to a Date object?

Question

I have a date_select in my view inside a form, however on submit the value returned is in a hash form like so:

{"(1i)"=>"2010", "(2i)"=>"8", "(3i)"=>"16"}

how can i convert that in to a Date format in rails so i can use it as a condition when querying the database eg :condition => {:dates == :some_date_from_date_select} ? i tried calling Date.parse(:some_date_from_date_select) but it didn't work because its expecting a string and not a hash map.

is there a rails way to do this?

thanks

Answer 1

I don't know about a rails way, but this "one-liner" does the trick:

irb(main):036:0> d = Date.parse( {"(1i)"=>"2010", "(2i)"=>"8", "(3i)"=>"16"}.to_a.sort.collect{|c| c[1]}.join("-") )
=> #<Date: 4910849/2,0,2299161>
irb(main):037:0> d.to_s
=> "2010-08-16"

Or, with less magic:

h={"(1i)"=>"2010", "(2i)"=>"8", "(3i)"=>"16"}
d=Date.new(h['(1i)'].to_i, h['(2i)'].to_i, h['(3i)'].to_i)
d.to_s
=> "2010-08-16"

Answer 2

I have a short one line solution for this

params["due_date"] = {"date(3i)"=>"14", "date(2i)"=>"4", "date(1i)"=>"2014"}


params["due_date"].map{|k,v| v}.join("-").to_date
=> Mon, 14 Apr 2014

Answer 3

Here's a generic way to do it, which also supports partial dates/times and empty fields:

def date_from_date_select_fields(params, name)
  parts = (1..6).map do |e|
    params["#{name}(#{e}i)"].to_i
  end

  # remove trailing zeros
  parts = parts.slice(0, parts.rindex{|e| e != 0}.to_i + 1)
  return nil if parts[0] == 0  # empty date fields set

  Date.new(*parts)
end

Example usage:

# example input:
#
# params = {
#   "user":
#     "date_of_birth(1i)": "2010",
#     "date_of_birth(2i)": "8",
#     "date_of_birth(3i)": "16"
#   }
# }
date_of_birth = date_from_date_select_fields(params[:user], 'date_of_birth')

Answer 4

Date.new(*params["due_date"].values.map(&:to_i))

Note: Works in ruby 1.9.2+ since it depends on the order of the hash elements.

Two goodies here:

• Symbol to Proc
• Splat operator

Answer 5

This particular code (the one that does conversion) can be tracked from lib/active_record/connection_adapters/abstract/schema_definitions.rb , line no 67 onwards, ie the method type_cast .

These two methods are used to generate a date from string:

def fast_string_to_date(string)
  if string =~ Format::ISO_DATE
    new_date $1.to_i, $2.to_i, $3.to_i
  end
end

# Doesn't handle time zones.
def fast_string_to_time(string)
  if string =~ Format::ISO_DATETIME
    microsec = ($7.to_f * 1_000_000).to_i
    new_time $1.to_i, $2.to_i, $3.to_i, $4.to_i, $5.to_i, $6.to_i, microsec
  end
end

# Note that ISO_DATE is:
ISO_DATE = /\A(\d{4})-(\d\d)-(\d\d)\z/