Ruby sort by multiple values?

Question

I have an array of hashes:

a=[{ \'foo\'=>0,\'bar\'=>1 },
   { \'foo\'=>0,\'bar\'=>2 },
   ... ]

I want to sort the array first

Answer 1

This error appeares when you have unstable keys and trying to sort by them. Example:

[{'foo'=>99,'bar'=>1},{'foo'=>0,'bar'=>2, 'qwe' => 7}]
a.sort_by{|v| v['qwe']}
ArgumentError: comparison of NilClass with 7 failed

Try to do

a.sort_by{|v| [v['qwe']].select{|k| not k.nil?}}

But it doesnt work for me in

[v['index'],v['count'],v['digit'],v['value']]

where digit is unstable