Why is this string key in a hash converted to a symbol?

Question

Using Ruby 2.3:

In example 1, the string key "a" is automatically converted to a symbol, whereas with example 2, it stays a string.

Example 1

{"a": 1} # => {:a=>1}  

Example 2

{"a"=>"c"} # => {"a"=>"c"} 

I thought : was the same as the old style hash rocket => syntax. What is going on? Why have I never noticed this in Rails? Is it the HashWithIndifferentAccess that is obscuring this?

Answer 1

In Ruby 2.3(.0), these are all the same:

{:"a" => 1} {"a": 1}, {:a => 1} {a: 1}  

They all translate to the same thing: a is a symbol in all these cases.

{"a"=>1} is different: a is a string in this case.

Answer 2

It's because of the new hash syntax introduced with ruby 1.9. The syntax with colon works with symbol keys only. It's called a "symbol to object" hash and it's only syntactic sugar for the most common style of hashes out there. Another point for me, it's closer to the javascript object notation.

If I have mixed key types then I prefer the old style (hash-rocket syntax), but that's up to you. Mixing the two style looks ugly to me.