在ruby中排序或映射两个数组

Question

I have a section array ['part one','part two'] and an array of item objects [item1,item2,item3] .

Each item object has a section attribute ( in this case with the value of 'part one' or'part two') and an order attribute which is an integer.

I want to create an array like

[ ['part one',[item1,item3]],['part two',[item3]] ]

or

[['part one',item1,item3],['part two',item3]]

where

item1.section == 'part one' and item1.order == 1, 
item3.section == 'part one' and item3.order == 2, 
item2.section == 'part two' and item2.order == 1

Answer 1

To group by section , and order by order you can do the following:

items.sort_by(&:order).group_by(&:section).to_a
# => [["part one", [item1, item3]], ["part two", [item2]]]

sort_by orders all the items according to the order attribute, while group_by groups them into a hash of arrays, each key is a different section . to_a turns the hash into an array.

---

If you want to keep the order of the section list, you can use it to define the order instead of to_a :

grouped = items.sort_by(&:order).group_by(&:section)
# => { "part one" => [item1, item3], "part two" => [item2] }
sorted = sections.zip(sections.map { |s| grouped[s] })
# => [["part one", [item1, item3]], ["part two", [item2]]]