Ruby Syntax ":attr =>" vs. "attr:"?

Question

Is this code aquivalent

class Product < ActiveRecord::Base
  validates :legacy_code, :format => { :with => /\A[a-zA-Z]+\z/,
    :message => "Only letters allowed" }
end

to this code:

class Product < ActiveRecord::Base
  validates :legacy_code, format: { with:/\A[a-zA-Z]+\z/,
    message:"Only letters allowed" }
end

??

This sort of thing can be easily verified using IRB. Compare `{:a=>1}` with `{a:1}`. — the Tin Man, Nov 17 '12 at 15:33
@theTinMan: But then you'll fall into the trap of thinking that `{:$n=>1}` and `{$n:1}` are the same thing when they're not. — mu is too short, Nov 17 '12 at 17:13
possible duplicate of [Is there any difference between the \`:key => "value"\` and \`key: "value"\` hash notations?](http://stackoverflow.com/questions/8675206/is-there-any-difference-between-the-key-value-and-key-value-hash-no) — mu is too short, Nov 17 '12 at 17:31

score 2 · Accepted Answer · answered Nov 17 '12 at 12:57

2

Yes, this codes are equivalent in ruby 1.9.
{:key => vales} - is a hash syntax in ruby 1.8
{key: value} - is a new hash syntax, it was added in ruby 1.9

answered Nov 17 '12 at 12:57

Alexander Randa

868
4
7

score 1 · Answer 2 · answered Nov 17 '12 at 13:01

Yes. As long you aren't using Ruby 1.8, you can use {a: 'b'} syntax. It does exactly what {:a => 'b'} does, it's just shorter.

When ran in IRB, both examples show identical results (in Ruby 1.9).

$ irb1.9
irb(main):001:0> {:a => 'b'}
=> {:a=>"b"}
irb(main):002:0> {a: 'b'}
=> {:a=>"b"}
irb(main):003:0>

But when running in Ruby 1.8, {a: 'b'} doesn't work.

$ irb1.8
irb(main):001:0> {:a => 'b'}
=> {:a=>"b"}
irb(main):002:0> {a: 'b'}
SyntaxError: compile error
(irb):2: odd number list for Hash
{a: 'b'}
   ^
(irb):2: syntax error, unexpected ':', expecting '}'
{a: 'b'}
   ^
(irb):2: syntax error, unexpected '}', expecting $end
        from (irb):2
irb(main):003:0>

No, it doesn't do exactly the same thing. The JavaScript notation is limited to a subset of symbol keys whereas the hashrocket works with any valid key. More details over here: http://stackoverflow.com/a/8675314/479863 — mu is too short, Nov 17 '12 at 17:34

score 0 · Answer 3 · answered Nov 17 '12 at 12:57

0

If you are using ruby 1.9 then it is valid and also equivalent.

answered Nov 17 '12 at 12:57

krichard

3,699
24
34

Ruby Syntax ":attr =>" vs. "attr:"?

3 Answers3