Rails hash confusion

13 Mar

One of the things that confused and intimidated me when first encountering Rails (I’m a newbie, so we’re talking 3.2 here) was the preponderance of colons ‘:’ and their seemingly ever-shifting whereabouts.

:controller (sometimes on the left)
controller: (sometimes on the right)

While it may seem silly to some, these little seeming inconsistencies, taken at a gulp while perusing a page of code, made my eyes blur and led me to quickly conclude that whatever voodoo it was that some folks were in command of to understand so many tiny details and nuances of syntax, I didn’t understand it a bit.

I did understand the idea of a Ruby symbol:

:cats

And I understood the idea of a hash:

{ :cats => "animal" }

But nowhere in Ruby had I seen a colon on the right!

Cutting to the chase:

Turns out it’s just an update in Rails that gives developers a short-hand alternative for writing hashes. They probably find it difficult to imagine how anyone could be anything but dazzled at the newfound convenience!

:controller => :posts
or
:cats => "Frisky"

and

controller: :posts
or
cats: "Frisky"

…are the exact same thing in later versions of Rails. Colon to the left with a hashrocket ( => ), or to the right without. That’s it.

A convenience for those already familiar with Rails conventions, but a possible point of confusion for newbies trying to parse out the syntax.

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