greetings

Discussion in 'Ruby' started by Mage, Jan 23, 2006.

  1. Mage

    Mage Guest

    Hello,

    some months ago I started to use Python and to see the light.

    Now my eyes are a bit burned so I went back to the darkness (for some
    glittering red gem). I started Ruby.

    I read almost the whole pragmatic programmer book without writing a
    piece of code, except this: 15.times { puts 'I love you, xxx'}, where
    xxx were my girlfriend's name. From that moment she also started to like
    Ruby.

    It is a good book. However, it is based on Ruby 1.6. I failed to find
    something like "what changed from 1.6 to 1.8". Can you help me?

    Also, the reference is hard to read. It took a simple google session to
    find the quoted-printable method (Array.pack('M')). I think it could be
    easier to find in the manual.

    Setting up postgresql was quite easy (apt-get install libpgsql-ruby).
    The documented PGconn.open method generated error, it said that it is
    protected method. I use PGconn.new. Is it normal? I cannot skip the
    'port' parameter with the new method.

    On the whole I am happy with my first Ruby script and with the language
    itself.

    Mage
     
    Mage, Jan 23, 2006
    #1
    1. Advertisements

  2. Mage

    Joe Van Dyk Guest

    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.=20
    http://whytheluckystiff.net/articles/rubyOneEightOh.html
     
    Joe Van Dyk, Jan 23, 2006
    #2
    1. Advertisements

  3. Hello and welcome to Ruby.
    Actually, the current version of the Pickaxe covers very modern Ruby:

    http://www.pragmaticprogrammer.com/titles/ruby/index.html

    I strongly recommend picking it up.
    The top hit from Google for "What's new in Ruby 1.8" is:

    http://whytheluckystiff.net/articles/rubyOneEightOh.html

    ;)

    James Edward Gray II
     
    James Edward Gray II, Jan 23, 2006
    #3
  4. Mage

    Mage Guest

    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
     
    Mage, Jan 23, 2006
    #4
  5. Mage

    Gene Tani Guest

    these articles on symbols were written for you:

    http://glu.ttono.us/articles/2005/08/19/understanding-ruby-symbols
    http://onestepback.org/index.cgi/Tech/Ruby/SymbolsAreNotImmutableStrings
    http://www.oreillynet.com/ruby/blog/2005/12/digging_into_ruby_symbols.html
    http://www.oreillynet.com/ruby/blog/2005/12/symbols_strings_methods_and_va.html
    http://microjet.ath.cx/WebWiki/2005.12.27_UsingSymbolsForTheWrongReason.html
    http://www.rubycentral.com/faq/rubyfaqall.html#s6
    http://moonbase.rydia.net/mental/blog/programming/ruby-symbols-explained.html
     
    Gene Tani, Jan 23, 2006
    #5
  6. Mage

    Zach Guest

    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 }

    you can refer to the parameters as :x and :y. As opposed to mandating
    the prototype of the method being center(x, y).

    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.

    -Zach
     
    Zach, Jan 23, 2006
    #6
  7. 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 =3D> 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.
    Well, in a Hash they are called keys.
    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.
    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.
     
    Mark Volkmann, Jan 23, 2006
    #7
  8. Michael Bannister, Jan 23, 2006
    #8
  9. Mage

    Mage Guest

    I think I understand now, thanx.
    Actually, database connection parameters are good example for variable
    length arguments. Sometimes you want to skip the port number and the
    authentication data, other times you want only defne the user and the
    database name.

    Mage
     
    Mage, Jan 23, 2006
    #9
  10. Mage

    Zach Guest

    Exactly. I see Rails using this especially in generating views from ERB.
    "Almost" every parameter can be omitted depending on how you want to
    generate the view. (I'm mainly talking about the helper tags).

    -Zach
     
    Zach, Jan 23, 2006
    #10
  11. Mage

    Zach Guest

    "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
     
    Zach, Jan 23, 2006
    #11
  12. In your previous example, you ARE passing a Hash to the link_to
    method. Whenever all the parameters at the end are of the form "key =3D>
    value", Ruby automatically turns them into a single Hash object and
    passes that to the method.

    When you send a block to a method, you are giving it code that it can
    choose to execute any number of times. The block always follows the
    parameter list and must begin on the same line as the closing paren.
    It starts with either "do" or "{".
     
    Mark Volkmann, Jan 23, 2006
    #12
  13. Mage

    Zach Guest

    Great, thanks for the clarification!

    -Zach
     
    Zach, Jan 23, 2006
    #13
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.