What the hell is the => operator?

ruby-talk
1

I've seen this in some ruby code but I have no idea what is going on.
I'd do a google search on it but... I don't search for '=>' and I don't know
how to describe it in english so that the context will be this!
    I've seen this operator used in, what seems to me, to be totally bizarre
contexts. As far as I know, it's only used in hash definitions. However,
it's used in both Rails and scRUBYt. It looks something like this:

method_call :symbol => false do
    # do something here
end

another_method random_var, :symbol => :other_symbol do
    # do something else
end

    Can someone explain to me what is going on here?
    Thank you...

2

It's mostly 'syntactic sugar'. In Ruby you can leave the curly braces {} in a method call away in case the last values form a hash.

For example:

method_call( param_1, param_2, :sym1 => 'something', 'another_key' => :another_value )

Note that you're not limited to symbols as hash keys.

The following examples are esentially the same:

method_call( :symbol => false ) do
    # do something here
end

another_method( random_var, :symbol => :other_symbol ) do
    # do something else
end

method_call( { :symbol => false } ) do
    # do something here
end

another_method( random_var, { :symbol => :other_symbol } ) do
    # do something else
end

'=>' is used to point from a hash key to its value.

Happy rubying

Stephan

···

Am Freitag, den 02. November 2007 um 09.06 Uhr schrieb Just Another Victim of the Ambient Morality <ihatespam@hotmail.com>:

   I've seen this in some ruby code but I have no idea what is going on.
I'd do a google search on it but... I don't search for '=>' and I don't know
how to describe it in english so that the context will be this!
   I've seen this operator used in, what seems to me, to be totally bizarre
contexts. As far as I know, it's only used in hash definitions. However,
it's used in both Rails and scRUBYt. It looks something like this:

method_call :symbol => false do
   # do something here
end

another_method random_var, :symbol => :other_symbol do
   # do something else
end

   Can someone explain to me what is going on here?

3

Just Another Victim of the Morality wrote:

    Can someone explain to me what is going on here?
    Thank you...

def methA(arg)
  p arg
end

methA({'a'=>10})
methA('a'=>10)
methA 'a'=>10

--output:---
{"a"=>10}
{"a"=>10}
{"a"=>10}

def methB(arg)
  p arg
end

methB({'a'=>10, 'b'=>20})
methB('a'=>10, 'b'=>20)
methB 'a'=>10, 'b'=>20

--output:--
{"a"=>10, "b"=>20}
{"a"=>10, "b"=>20}
{"a"=>10, "b"=>20}

def methC(arg1, arg2)
  p arg1, arg2
end

methC(12.3, {'a'=>10, 'b'=>20})
methC(12.3, 'a'=>10, 'b'=>20)
methC 12.3, 'a'=>10, 'b'=>20

--output:---
12.3
{"a"=>10, "b"=>20}
12.3
{"a"=>10, "b"=>20}
12.3
{"a"=>10, "b"=>20}

···

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