如何为给定日期时间的每个日期创建一个哈希/数组次数

Question

I have a column with datetime in a table that has the format:

2012-10-30 08:00:00 UTC

How could I create an array or hash that would collect the times by date:

2012-10-30
  8:00
  9:00
  13:00 
2012-11-02
  8:00
  9:00

In the end I would like to have web output like this:

October 30, 2012
  8:00   <reserve button>
  9:00   <reserve button>
  13:00  <reserve button>

November 2, 2012
  8:00   <reserve button>
  9:00   <reserve button>

I can figure out the html part if I can get the array correctly setup.

Answer 1

Get all your available timestamps from the table, for example:

available_times = SomeTable.select(:some_column).order(:some_column).all

Build a Hash by date:

@result = available_times.inject({}) do |m, timestamp| 
  date = timestamp.to_date
  m[date] ||= []
  m[date] << timestamp
  m
end

@result will be a Hash by date with available times.

You can now do this in your view:

<% @result.each do |date, timestamps| -%>
  <div><%= date.strftime("%B %-d, %Y") %></div>
   <% timestamps.each do |timestamp| -%> 
     <%= timestamp.strftime("%k:%M") %>  <input id='<%= timestamp.to_f%>' type='button' value='Reserve Button'/>
     <br/>
   <% end -%>
<% end -%>

Answer 2

sample = ["2012-10-28 08:30:00 UTC", 
          "2012-10-28 09:00:00 UTC", 
          "2012-11-30 09:15:00 UTC", 
          "2012-11-30 08:00:00 UTC"]

sample.each_with_object(Hash.new{ |h, k| h[k] = [] }) do |d, h|
  date = DateTime.parse(d)
  h[date.strftime("%B %-d, %Y")] << date.strftime("%k:%M")
end
# => {"October 28, 2012"=>["8:30", "9:00"], "November 30, 2012"=>["9:15", "8:00"]}