Hash does not contain 'try' method

Question

I am noticing differences between a hash object within Ruby 1.8.7 and a hash object within Rails 3.0.10.

For example, within the 1.8.7 irb, I get:

1.8.7 :001 > {}.try(:method)
NoMethodError: undefned method `try' for {}:Hash
from (irb):1```

However, from the 3.0.10 rails console, I get:

1.8.7 :003 > {}.try(:method_x)
NoMethodError: undefined method `method_x' for {}:Hash
  from (irb):3:in `try'
  from (irb):3

This surprises me because I was under the impression that try is defined in Object which is an ancestor of Hash and try will return nil instead of throwing a NoMethodError.

What am I missing?

score 12 · Accepted Answer · answered Mar 09 '12 at 00:54

12

This surprises me because I was under the impression that try is defined in Object which is an ancestor of Hash and try will return nil instead of throwing a NoMethodError.

What am I missing?

Your impression of which class try is defined in is correct (Object). What you are missing is what file it is defined in. It's defined in the ActiveSupport library, not in the Ruby core library.

So, you need to

require 'active_support/core_ext/object/try'

first.

answered Mar 09 '12 at 00:54

Jörg W Mittag

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Yeah, I discovered that Rails monkeypatches Object and adds in `try,` which was a surprise to me. – David Weiser Mar 09 '12 at 17:14

score 1 · Answer 2 · answered Mar 08 '12 at 17:26

1

try is not part of ruby 1.8.7, though Rails does include it through ActiveSupport. try is part of Object from ruby 1.9+ (afaik).

answered Mar 08 '12 at 17:26

James Brooks

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No, `try` is not a part of Ruby even post 1.9 – Lee Jarvis Mar 09 '12 at 00:59

Hash does not contain 'try' method

2 Answers2