Extending Array and assigning to self

Discussion in 'Ruby' started by Oliver Saunders, May 6, 2008.

  1. I've got this class that is essentially an array with a few things
    added. Here's some of it:

    class Pages

    def initialize
    @content = []
    end

    def import(file, page_delimiter = ' ')
    @content = file.read.split page_delimiter
    self
    end

    def [](num)
    @content[num]
    end

    def <<(page_content)
    @content << page_content
    end

    ....

    Because I'm basically reimplementing Array I thought it might me more
    sense to inherit from Array or delegate to Array. The trouble is that I
    need to assign to @content. How do you suggest I get round this problem?
     
    Oliver Saunders, May 6, 2008
    #1
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  2. Oliver Saunders

    yermej Guest

    I would just use Array's own methods. E.g.:
    class Pages < Array
    def import(file, page_delimiter = ' ')
    self.clear
    self.concat file.read.split.page_delimiter
    end
    end

    I'm not sure if Array#concat is the best choice here (for some
    definition of best), but it'll work.
     
    yermej, May 6, 2008
    #2
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  3. Fantastic yermej. I didn't know about that concat method.

    Next point: What if I have a similar problem with strings? I'd like to
    achieve this:

    # is a string
    x = ValueChangeString.new 'foo' #=> 'foo'
    # has all the methods of string already
    x.length #=> 3
    # But also has methods that completely alter the string's value
    # whilst remaining the same object
    x.change_value! #=> 'bar'
     
    Oliver Saunders, May 6, 2008
    #3
  4. Hi --

    That's actually a space before page_delimiter, not a dot. Or:

    file.read.split(page_delimiter)

    just to be sure :)
    In general I'd use #replace rather than #clear plus #concat.


    David

    --
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    See http://www.rubypal.com for details and updates!
     
    David A. Black, May 6, 2008
    #4
  5. In general I'd use #replace rather than #clear plus #concat.
    Whoa! That answers the string question. Thanks :)
     
    Oliver Saunders, May 6, 2008
    #5
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