Ruby => operator... eg: :text => /Log In/

Question

What does this do? I find the example here, but other than what it does, what does it mean? I can't find anything on google because well, I am not sure what '=>' is even called in this context.

More examples here: http://mechanize.rubyforge.org/mechanize/EXAMPLES_rdoc.html

Answer 1

It associates a value with an index for hashes.

obj.method :text => /Log In/

is shorthand for

obj.method {:text => /Log In/}

Answer 2

In :text => /Log In/, you are passing a hash to page's link_with function, and the key in the hash is :text and its corresponding value is /Log In/.

Basically: :x => y means that :x is a key in a hash that maps to a value of y.

passing hashes to functions like this allows you to have something like (but not exactly) named parameters.

UPDATE:

A symbol of the form :something is called.... a symbol! You can think of them sort of like global string constants (but they're not quite the same). Now, when you think back to something like:

 login_page.form_with(:action => '/account/login.php')

What you're actually doing is constructing a new hash on the fly. You create a new element in the hash, where the key is a string with the value "action", and the value of that element is "/account/login.php" (in this case, also a string, but I'm pretty sure you can store other things in hashes besides strings).

...whew! It's been a while since I've worked with Ruby. I hope I got that all correct. ;)

Some good looking pages here (more can be found by searching google for "ruby symbol")

http://glu.ttono.us/articles/2005/08/19/understanding-ruby-symbols

http://www.troubleshooters.com/codecorn/ruby/symbols.htm#_What_are_symbols

Answer 3

It's used to create a hash expression, as in { key => value }.

Also, when used as the last parameter in a method call, the { } are not needed, so the key => value can appear alone.

>> p({:a => 1, :b => 2})
{:a=>1, :b=>2}
=> nil
>> p :c=>3, :d=>4
{:d=>4, :c=>3}
=> nil
>> t = { :e=>5, :f=>6 }
=> {:f=>6, :e=>5}

This shorthand is really nice in poetry mode, where a literal hash following a method name would look like a block.