What's the difference `{'x'=> 3}` and `{x: 3}`?

Question

I have this:

a = {'x' => 3}
b = {'x': 3}
c = {x: 3}
d = {:x => 3}
e = {:'x' => 3}

So, I have that b = c = d = e = {:x => 3}, meanwhile a = {"x" => 3} but a.class == b.class.

I don't understand what the difference is between a and the rest of variables.

sorry, I ment, the boolean validation between both object class is true. — Iván Cortés, Apr 04 '16 at 03:13
Possible duplicate of [In Ruby what is the meaning of colon after identifier in a Hash?](http://stackoverflow.com/questions/10645668/in-ruby-what-is-the-meaning-of-colon-after-identifier-in-a-hash) — SwiftMango, Apr 04 '16 at 03:37

Petr Gazarov · Answer 1 · 2016-04-04T03:34:07.633

2

Your variable a hash has "x" key as a string, while other variables have that key as symbol.

Calling class on an object in Ruby returns its class, in your example it is Hash. In other words, the constructor of all hash instances, such as {x: 3} is Hash object.

edited Apr 04 '16 at 03:34

answered Apr 04 '16 at 03:19

Petr Gazarov

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score 2 · Accepted Answer · edited Apr 04 '16 at 07:39

2

In b,c,d, and e, the key is a Symbol.

In a, the key is a String.

a = { 'x' => 3 }  #=> { "x" => 3 } 
b = { 'x': 3 }    #=> { :x => 3 }
c = { x: 3 }      #=> { :x => 3 }
d = { :x => 3 }   #=> { :x => 3 }
e = { :'x' => 3 } #=> { :x => 3 }

edited Apr 04 '16 at 07:39

spickermann

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answered Apr 04 '16 at 03:31

cozyconemotel

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score 0 · Answer 3 · edited May 23 '17 at 10:28

There is a significant difference between String and Symbol classes in ruby:

By convention, all but the very first hash notations cast keys to the Symbol instance, while the first one uses the key (String instance in this particular case) as is. (To be more precise: b and c cast key to the Symbol instance, d and e do not cast anything, but keys given in these cases are Symbol instances already.)

Since ('x' == :x) == false, a hash differs from the latters.

What's the difference `{'x'=> 3}` and `{x: 3}`?

3 Answers3