Why can't I read a value from a hash?

Question

Considering the following code:

  hash = {"a"=>["B", "C"], "b"=>["C"], "c"=>["D", "E"], "d"=>["F"]}
  puts hash["a"]

This just prints nothing.

puts hash["a"].class

This prints NilClass

Is there some kind of known bug in the following ruby version?

ruby 2.0.0p247 (2013-06-27 revision 41674) [universal.x86_64-darwin13]

I hope someone can help me out, this is driving me crazy. My IDE is RubyMine from JetBrains. I also tried to run it directly via IRB.

Thanks

PS. OS is OSX

Not an answer as to why this is happening but why dont you try to use symbols as indexes in the hash: `hash = {:a=>["B", "C"], :b=>["C"], :c=>["D", "E"], :d=>["F"]}` and this way `puts hash[:a]` works — Agush, Apr 22 '14 at 20:17
Hey thanks for your comment. I havent done that because I am setting the keys dynamic — Sjaak Rusma, Apr 22 '14 at 20:27
Try setting the keys with the `.to_sym` method of String http://apidock.com/ruby/String/to_sym — Agush, Apr 22 '14 at 20:29
Aha, works great. But look at the answer below. This will also convert the weird 65279 to a symbol.. — Sjaak Rusma, Apr 22 '14 at 20:33
Yeah there seems to be a problem with your input then, you should sanitize it before converting it to a hash :/ — Agush, Apr 22 '14 at 20:35
Your `"a"` key has a [BOM](http://en.wikipedia.org/wiki/Byte_order_mark) (byte-order-mark) as the first character. You need to open the file using the appropriate encoding. At a guess I'd say you're working with UTF-16LE. — the Tin Man, Apr 22 '14 at 21:39

score 7 · Accepted Answer · edited May 23 '17 at 12:28

7

By copying your code and pasting it in my console, I could reproduce your problem.

Then I took your hash and did the following:

hash.first.first
# => "a"
hash.first.first.length
# => 2

!!!

It seems that your "a" has an unprintable first char. Delete it, and you'll be fine.

And you char is What is this char? 65279 '':

hash.first.first[0].ord
# => 65279

edited May 23 '17 at 12:28

Community

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answered Apr 22 '14 at 20:17

Uri Agassi

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Pfff after hours of debugging this appears to be the case.. I am reading the values out of a .txt file. Not sure how I am going to fix this.. Super thanks anyhow – Sjaak Rusma Apr 22 '14 at 20:32
Wow, this is remarkable. If I add one empty line at the beginning of the file everything works. – Sjaak Rusma Apr 22 '14 at 20:35
@SjaakRusma or you could try this when reading the file: http://stackoverflow.com/a/7780559/481229 – Agush Apr 22 '14 at 20:37
Removed the BOM with an HEX editor. Sad enough, doing things like File.open('foo', 'rb:BOM|UTF-16LE') do |fi| did not work. – Sjaak Rusma Apr 24 '14 at 14:56

score 2 · Answer 2 · answered Apr 22 '14 at 21:43

Your "a" key has a BOM (byte-order-mark) as the first character. You need to open the file using the appropriate encoding. At a guess I'd say you're working with UTF-16LE.

File.open('foo', 'rb:BOM|UTF-16LE') do |fi|
  ...
end

See http://www.ruby-doc.org/core-2.1.1/IO.html#method-c-new-label-IO+Encoding for more information.

Why can't I read a value from a hash?

2 Answers2

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