From: Zach <zacharooni@...>
Date: 2006-01-24T04:30:55+09:00
Subject: Re: greetings

"The fact that the right-hand side is surrounded by curly braces is
what makes it a Hash. Each key/value pair initially added to the Hash
looks like "key => value"."

I don't know about the braces, but I was meaning more about the 
Parenthesis (sorry about the type in the earlier example) for example:
|
link_to("View Article", :controller => "blah", :action => "yay", :id => 1)|

I guess I'm clueless as to what the difference is now between sending it 
a block and sending it parameterized symbols?

-Zach

Mark Volkmann wrote:

>On 1/23/06, Zach <zacharooni@comcast.net> wrote:
>  
>
>>I may be totally off base, being a Ruby Newbie myself, but I believe the
>>point of the :variable is sort of passing a HashMap to the method...for
>>instance:
>>
>>inside the method
>>    center = { :x => 1, :y => 2 }
>>    
>>
>
>The fact that the right-hand side is surrounded by curly braces is
>what makes it a Hash. Each key/value pair initially added to the Hash
>looks like "key => value". In this particular case, they decided to
>use symbols for keys which is pretty common. The colon means that the
>word following it is a symbol. They could have also used String keys.
>
>There was a long discussion about what symbols are recently, so I
>hesitate to try to simplify this, but here goes. Think of a symbol as
>a string that will be the same object in memory each time you use it.
>For example, "foo" and "foo" will be two different objects in memory,
>but :foo and :foo will refer to the same object.
>
>  
>
>>you can refer to the parameters as :x and :y.
>>    
>>
>
>Well, in a Hash they are called keys.
>
>  
>
>>As opposed to mandating
>>the prototype of the method being center(x, y).
>>    
>>
>
>That's a good point. Passing a Hash to a method, in a way, allows you
>to pass arbitrary parameters if you think of the keys as being
>parameter names the values as being parameter values.
>
>  
>
>>The benefits I can see are variable length arguments, and the arguments
>>placed don't have to be in the same order. Coming from java, I'm
>>actually a little wary about this, but I sort of understand the
>>usefulness, especially after reading the Rails book.
>>    
>>
>
>I don't think it's common in Ruby to use Hashes for this purpose.
>Usually methods have fixed parameters and you don't pass them in a
>Hash.
>
>  
>
>>Mage wrote:
>>
>>    
>>
>>>Joe Van Dyk wrote:
>>>
>>>      
>>>
>>>>On 1/23/06, Mage <mage@mage.hu> wrote:
>>>>
>>>>
>>>>
>>>>The second edition of the book was released two years ago or so and
>>>>covers Ruby 1.8.  You should read that one instead.
>>>>
>>>>Here's a pretty good summary of the changes in Ruby 1.8.
>>>>http://whytheluckystiff.net/articles/rubyOneEightOh.html
>>>>
>>>>
>>>>        
>>>>
>>>Thanx.
>>>
>>>One of the things I don't understand are the semicolons. When I read
>>>the Book, it said:
>>>
>>>class SomeThing
>>> atrr_reader :x, :y
>>>end
>>>
>>>I figured out that the attr_reader need to get the name of the
>>>instance variables.
>>>
>>>However, what is this code good for?
>>>
>>>def make_point_hash( point )
>>>  center = { :x => 1, :y => 2 }
>>>  big = { :r => 10 }
>>>  center.merge( big ).merge( point ) end
>>>make_point_hash( { :x => 20 } )
>>>
>>>#=> {:y=>2, :r=>10, :x=>20}
>>>
>>>What is that those semicolons do?
>>>
>>>    Mage
>>>
>>>
>>>
>>>
>>>
>>>      
>>>
>>    
>>
>
>
>--
>R. Mark Volkmann
>Partner, Object Computing, Inc.
>
>
>  
>