sort_by_this_array = [4,2,1,3] <-- This is array of attribute goal_id.
& then I have my
[<Todo id: 12, goal_id: 2]>, <Todo id: 13, goal_id: 2>, <Todo id: 6, goal_id: 1>, <Todo id: 7, goal_id: 2 >, <Todo id: 25, goal_id: 3 >, <Todo id: 30, goal_id: 1 >, <Todo id: 40, goal_id: 4 >]
Result should be: id: 40, 12,13,7, 6,30, 25
I'm thinking about 2 loops & it's definitely not the best way.
Maybe try this approach:
S = Struct.new(:id, :v)
a = Array.new(5) { |i| S.new(i, i) }
a.shuffle!
a.sort_by {|e| [2, 3 , 1 , 4, 0].index(e.id) }
It will return your a in order by ids.
You may want to use variation of sorting by selection where swapping would occur each time you find a 'todo' element for which its 'goal_id' attribute is equal to 'goal_id' from your array.
Todo = Struct.new(:id, :goal_id)
todos = [Todo.new(12,2), Todo.new(13,2),Todo.new(6,1), Todo.new(7,2), Todo.new(25,3), Todo.new(30,1), Todo.new(40,4)]
sort_by_this_array = [4,2,1,3]
j = 0
sort_by_this_array.each do |goal_id|
todos.each_with_index do |todo,i|
if todo.goal_id == goal_id
todos[i],todos[j] = todos[j],todos[i]
j += 1
end
end
end
I would reccommend reading some sources on the web about sorting by selection. As this is a simple variation of it http://www.sorting-algorithms.com/selection-sort
Unfortunately this solution will not preserve order of elements inside initial todos array, as each swapping changes the position on which todo element is located. So they will be sorted, but it will be not stable.
Below stable solution with additional memory.
j = 0
results = []
sort_by_this_array.each do |goal_id|
while idx = todos.index {|e| e.goal_id == goal_id}
results << todos[idx]
todos.delete_at(idx)
end
end
a.sort_by {|e| [2, 3 , 1 , 4, 0].index(e.id) } will not preserve initial order as well as in some cases using sort_by may be just inefficient. For more information I would suggest reading information at following site: apidock.com/ruby/Enumerable/sort_by. Sometimes one liners aren't best option (in terms of performance), but it very depends on your use case.
