Let's say you define a simple Hash.
irb(main):001:0> h1 = {"a"=>1,"b"=>2,"c"=>3}
=> {"a"=>1, "b"=>2, "c"=>3}
What do you think you'll get when you send an each message to it? I figured either a, b, c or 1, 2, 3. Surprise:
irb(main):003:0> h1.each{|a| puts a}
a
1
b
2
c
3
=> {"a"=>1, "b"=>2, "c"=>3}
It all comes out, keys and values interleaved.
Now, the trick becomes figuring out what to Google for to learn the syntax that gets you just the part of the hash you're after. Let me save you a little time. What you're after is each_value.
irb(main):008:0> h1.each_value {|a| puts a}
1
2
3
=> {"a"=>1, "b"=>2, "c"=>3}
You can also use each_key. Fairly intuitive, once you know it. Ah, there's the rub. :-)
irb(main):009:0> h1.each_key {|a| puts a}
a
b
c
=> {"a"=>1, "b"=>2, "c"=>3}
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Comments[2]
Posted by lee on August 17, 2005 2:26:33 PM EDT
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Re: Iterating over a Hash in Ruby
Your problem was that the block Hash#each takes is really looking for a |key, value| .
Your code should read:
h1.each { |key, val| ... }
http://ruby-doc.org/core/classes/Hash.html#M000635
Comment from Tony on August 18, 2005 12:45:37 PM EDT
Yep, cool. Thanks, Tony!
irb(main):043:0> h1.each{|k,v| puts "#{k} ---> #{v}"}
a ---> 1
b ---> 2
c ---> 3
=> {"a"=>1, "b"=>2, "c"=>3}
This reminds me of something else that has been bugging me since I saw it. What does this syntax mean?
def list @category_pages, @categories = paginate :category, :per_page => 10, :order_by => 'category' endHow can Ruby return two values from the paginate method?!
Comment from lee on August 22, 2005 9:22:39 AM EDT
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