When to use : before variables?

daniel · December 4, 2005, 6:50pm

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

Thanks in advance.

daniel · December 4, 2005, 6:54pm

Look up Symbols. The colon ( 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.

Ryan

daniel · December 4, 2005, 7:06pm

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
other
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
ad-hoc
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.