From: reavey <reavey@...>
Date: 2003-02-19T20:57:35+09:00
Subject: Re: help: append error on Array push


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Thanks for you help
re-v

Matt Armstrong wrote:

>reavey <reavey@nep.net> writes:
>
>  
>
>>I get an error
>>"NameError: undefined method 'push' for nil from append"
>>as I'm working thru the Prag prog ruby book.
>>"""We'll start our class with a basic initialize method, which creates
>>the Array we'll use to hold our songs and store a reference to it in
>>the instance variable @songs
>>
>>class SongList
>>    def initialize
>>      @songs = Array.new
>>    end
>>    def append(aSong)
>>        @songs.push(aSong)
>>        self
>>    end
>>end
>>
>>list = SongList.new
>>list.
>>    append(Song.new('title1', 'artist1', 1)).
>>    append(Song.new('title2', 'artist2', 2))      """
>>    
>>
>
>The code you posted simply shouldn't report that error.  Here is my
>IRB session:
>
>irb(main):001:0> class SongList
>irb(main):002:1> def initialize
>irb(main):003:2> @songs = []
>irb(main):004:2> end
>irb(main):005:1> def append(song)
>irb(main):006:2> @songs.push(song)
>irb(main):007:2> self
>irb(main):008:2> end
>irb(main):009:1> end
>=> nil
>irb(main):010:0> list = SongList.new
>=> #<SongList:0x401c4c10 @songs=[]>
>irb(main):011:0> list.append("foo").append("bar")
>=> #<SongList:0x401c4c10 @songs=["foo", "bar"]>
>
>P.S. for this test it doesn't matter what objects you pass to
>SongList#append, since it just appends it to the @songs array.
>
>  
>


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Thanks for you help<br>
re-v<br>
<br>
Matt Armstrong wrote:<br>
<blockquote type="cite" cite="mid87heb0pzg2.fsf@squeaker.lickey.com">
  <pre wrap="">reavey <a class="moz-txt-link-rfc2396E" href="mailto:reavey@nep.net">&lt;reavey@nep.net&gt;</a> writes:

  </pre>
  <blockquote type="cite">
    <pre wrap="">I get an error
"NameError: undefined method 'push' for nil from append"
as I'm working thru the Prag prog ruby book.
"""We'll start our class with a basic initialize method, which creates
the Array we'll use to hold our songs and store a reference to it in
the instance variable @songs

class SongList
    def initialize
      @songs = Array.new
    end
    def append(aSong)
        @songs.push(aSong)
        self
    end
end

list = SongList.new
list.
    append(Song.new('title1', 'artist1', 1)).
    append(Song.new('title2', 'artist2', 2))      """
    </pre>
  </blockquote>
  <pre wrap=""><!---->
The code you posted simply shouldn't report that error.  Here is my
IRB session:

irb(main):001:0&gt; class SongList
irb(main):002:1&gt; def initialize
irb(main):003:2&gt; @songs = []
irb(main):004:2&gt; end
irb(main):005:1&gt; def append(song)
irb(main):006:2&gt; @songs.push(song)
irb(main):007:2&gt; self
irb(main):008:2&gt; end
irb(main):009:1&gt; end
=&gt; nil
irb(main):010:0&gt; list = SongList.new
=&gt; #&lt;SongList:0x401c4c10 @songs=[]&gt;
irb(main):011:0&gt; list.append("foo").append("bar")
=&gt; #&lt;SongList:0x401c4c10 @songs=["foo", "bar"]&gt;

P.S. for this test it doesn't matter what objects you pass to
SongList#append, since it just appends it to the @songs array.

  </pre>
</blockquote>
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