Array to Hash Ruby

Question

Okay so here s the deal  I ve been googling for ages to find a solution to this and while there are many out there  they don t seem to do the job I m looking for   Basically I have an array structured like this     item 1    item 2    item 3    item 4      I want to convert this to a Hash so it looks like this      item 1    gt   item 2    item 3    gt   item 4      i e  the items that are on the  even  indexes are the keys and the items on the  odd  indexes are the values    Any ideas how to do this cleanly  I suppose a brute force method would be to just pull out all the even indexes into a separate array and then loop around them to add the values

User · Answer

a     item 1    item 2    item 3    item 4   Hash  a each slice  2   map    e  e       or  if you hate Hash          a each slice  2   each with object Hash new do   k  v   h  h k    v end   or  if you are a lazy fan of broken functional programming   h   a lazy each slice  2   tap    a    break Hash new    h  k  h k    a find    e     e    k   1         gt     h  item 1      gt   item 2  h  item 3      gt   item 4

User · Answer

Enumerator includes Enumerable  Since 2 1  Enumerable also has a method  to h  That s why  we can write  -  a     item 1    item 2    item 3    item 4   a each slice 2  to h     gt    item 1   gt  item 2    item 3   gt  item 4     Because  each slice without block gives us Enumerator  and as per the above explanation  we can call the  to h method on the Enumerator object

User · Answer

Ruby 2 1 0 introduced a to h method on Array that does what you require if your original array consists of arrays of key-value pairs  http   www ruby-doc org core-2 1 0 Array html method-i-to h      foo   bar    1  2   to h     gt    foo   gt   bar  1   gt  2

User · Answer

This is what I was looking for when googling this     a  1    b  2   reduce        h  v  h merge v     gt    a  gt 1   b  gt 2

User · Answer

Just use Hash    with the values in the array  For example   arr    1 2 3 4  Hash  arr     gt  gives  1   gt  2  3   gt  4

User · Answer

All answers assume the starting array is unique  OP did not specify how to handle arrays with duplicate entries  which result in duplicate keys   Let s look at   a     item 1    item 2    item 3    item 4    item 1    item 5     You will lose the item 1   gt  item 2 pair as it is overridden bij item 1   gt  item 5   Hash  a    gt    item 1   gt  item 5    item 3   gt  item 4     All of the methods  including the reduce  amp  merge   result in the same removal    It could be that this is exactly what you expect  though  But in other cases  you probably want to get a result with an Array for value instead      item 1   gt   item 2    item 5     item 3   gt   item 4      The na  ve way would be to create a helper variable  a hash that has a default value  and then fill that in a loop   result   Hash new   hash  k  hash k           Hash new with block defines unique defaults  a each slice 2    k v  result k   lt  lt  v   a   gt    item 1   gt   item 2    item 5     item 3   gt   item 4      It might be possible to use assoc and reduce to do above in one line  but that becomes much harder to reason about and read

User · Answer

You could try like this  for single array   irb main  019 0 gt  a     item 1    item 2    item 3    item 4       gt    item 1    item 2    item 3    item 4   irb main  020 0 gt  Hash  a      gt    item 1   gt  item 2    item 3   gt  item 4     for array of array   irb main  022 0 gt  a     1  2    3  4       gt    1  2    3  4   irb main  023 0 gt  Hash  a flatten      gt   1  gt 2  3  gt 4

User · Answer

Or if you have an array of  key  value  arrays  you can do     1  2    3  4   inject     do  r  s    r merge   s 0    gt  s 1    end     gt    1   gt  2  3   gt  4

User · Answer

a     item 1    item 2    item 3    item 4   h   Hash  a      gt     item 1    gt   item 2    item 3    gt   item 4      That s it  The   is called the splat operator   One caveat per  Mike Lewis  in the comments    Be very careful with this  Ruby expands splats on the stack  If you do this with a large dataset  expect to blow out your stack    So  for most general use cases this method is great  but use a different method if you want to do the conversion on lots of data  For example   Lukasz Niemier  also in the comments  offers this method for large data sets   h   Hash a each slice 2  to a

[ruby] Array to Hash Ruby

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