When to use : before variables?

Hi out there,

after looking at rails and the pickaxe book (not totally red yet, just
used as a reference) I still wondering when to use just a construct

:a => something

What does it stands for and when to use it? Please apologize if it’s a
basic questions, but I can’t realize myself the usage.

If someone has a page no. in the pickaxe book, I’m glad to read the
chapter :wink:

Thanks in advance.

Look up Symbols. The colon (:slight_smile: is used to create them.

The basic idea is that if you are using a String as the key or value
for a hash in many places, it is more efficient to use a Symbol.


It helps not to think of :a as a variable (you won’t see it on
left-hand-side). It is an identifier called a ‘symbol’ or in some
languages an ‘atom’ or ‘interning.’ A symbol is guranteed to be the same
(for the same string) everywhere it is used. Atoms can be introduced
in your code and anywhere you use the same atom is assured to match
:foo !=
:bar but :foobar == :foobar. It is a space and time saver to use
symbols as
constants, keys etc. rather than using a string constant.

More on Pg. 308 of Pickaxe 2nd edition.

Hi Mark,

Mark E. wrote:

More on Pg. 308 of Pickaxe 2nd edition.

Thanks a lot. That are these kind of programming constructs I’ve to
learn. I’ll read the pages.