诗歌rails之 数组分组

关键字: rails in_groups_of

这次讲的是active_support/core_ext/array/grouping.rb里的in_groups_of方法

#   %w(1 2 3 4 5 6 7).in_groups_of(3) {|g| p g}
#   ["1", "2", "3"]
#   ["4", "5", "6"]
#   ["7", nil, nil]
#
#   %w(1 2 3).in_groups_of(2, ' ') {|g| p g}
#   ["1", "2"]
#   ["3", " "]
#
#   %w(1 2 3).in_groups_of(2, false) {|g| p g}
#   ["1", "2"]
#   ["3"]

 # %w(1 2 3 4 5 6 7).in_groups_of(3) {|g| p g} # ["1", "2", "3"] # ["4", "5", "6"] # ["7", nil, nil] # # %w(1 2 3).in_groups_of(2, ' ') {|g| p g} # ["1", "2"] # ["3", " "] # # %w(1 2 3).in_groups_of(2, false) {|g| p g} # ["1", "2"] # ["3"] 

in_groups_of的第一个参数指示几个元素一组，而第二个参数指示了当最后一组缺元素时用什么填补位置
我们可以几个一组来显示tasks了:

<table>
<% @tasks.in_groups_of(4,false) do |row_tasks| %>
  <tr>
    <% for task in row_tasks %>
      <td><%= task.name %></td>
    <% end %>
  </tr>
<% end %>
</table>

<table> <% @tasks.in_groups_of(4) do |row_tasks| %> <tr> <% for task in row_tasks %> <td><%= task.name %></td> <% end %> </tr> <% end %> </table> 

 # File vendor/rails/activesupport/lib/active_support/core_ext/array/grouping.rb, line 22
22: def in_groups_of(number, fill_with = nil)
23: if fill_with == false
24: collection = self
25: else
26: # size % number gives how many extra we have;
27: # subtracting from number gives how many to add;
28: # modulo number ensures we don't add group of just fill.
29: padding = (number - size % number) % number
30: collection = dup.concat([fill_with] * padding)
31: end
32:
33: if block_given?
34: collection.each_slice(number) { |slice| yield(slice) }
35: else
36: returning [] do |groups|
37: collection.each_slice(number) { |group| groups << group }
38: end
39: end
40: end

关键字: split(value = nil) {|element| ...}

  [1, 2, 3, 4, 5].split(3)                # => [[1, 2], [4, 5]]
  (1..10).to_a.split { |i| i % 3 == 0 }   # => [[1, 2], [4, 5], [7, 8], [10]]

     # File vendor/rails/activesupport/lib/active_support/core_ext/array/grouping.rb, line 90
 90:         def split(value = nil)
 91:           using_block = block_given?
 92: 
 93:           inject([[]]) do |results, element|
 94:             if (using_block && yield(element)) || (value == element)
 95:               results << []
 96:             else
 97:               results.last << element
 98:             end
 99: 
100:             results
101:           end
102:         end