How do I sort an array of hashes by a value in the hash?

Question

This Ruby code is not behaving as I would expect:

# create an array of hashes
sort_me = []
sort_me.push({"value"=>1, "name"=>"a"})
sort_me.push({"value"=>3, "name"=>"c"})
sort_me.push({"value"=>2, "name"=>"b"})

# sort
sort_me.sort_by { |k| k["value"]}

# same order as above!
puts sort_me

I'm looking to sort the array of hashes by the key "value", but they are printed unsorted.

Solution 1

Ruby's sort doesn't sort in-place. (Do you have a Python background, perhaps?)

Ruby has sort! for in-place sorting, but there's no in-place variant for sort_by in Ruby 1.8. In practice, you can do:

sorted = sort_me.sort_by { |k| k["value"] }
puts sorted

As of Ruby 1.9+, .sort_by! is available for in-place sorting:

sort_me.sort_by! { |k| k["value"]}

Solution 2

As per @shteef but implemented with the sort! variant as suggested:

sort_me.sort! { |x, y| x["value"] <=> y["value"] }

Solution 3

Although Ruby doesn't have a sort_by in-place variant, you can do:

sort_me = sort_me.sort_by { |k| k["value"] }

---

Array.sort_by! was added in 1.9.2

Solution 4

You can use sort_me.sort_by!{ |k| k["value"]}. This should work.

View more solutions

Comments

[Marc-André Lafortune]

Actually, Array#sort_by! is new in Ruby 1.9.2. Available today to all Ruby version by requiring my backports gem too :-)

[tekknolagi]

Hi, is there a way to sort in descending order too? I figure I might want to go 3,2,1...

[Stéphan Kochen]

You can't do that with sort_by, but use sort or sort! and simply flip the operands: a.sort! {|x,y| y <=> x } (ruby-doc.org/core-1.9.3/Array.html#method-i-sort)

[Zaz]

Or: puts sorted = sort_me.sort_by{ |k,v| v }

[Zaz]

@tekknolagi: Just append .reverse.

[Islam Azab]

@Shtééf It is doable via both methods.

[AMIC MING]

good source of information. Thanks, your answer really help me

[web spider26]

This "Array.sort_by! was added in 1.9.2" answer worked for me

[Salma Gomaa]

For reverse you can check: stackoverflow.com/a/38362351/1770571