Robert Klemme
6/9/2008 12:53:00 PM
2008/6/8 Rob Boellaard <rboell@tuparev.com>:
>
>
>
> Hello,
>
> I am trying to get some simple create/update/delete xml-element to
> work with REXML, but I run into trouble when writing to file. Here's a
> code example:
>
> def save
> file = File.open(@@filePath, "r+")
> doc = Document.new(file)
> root = doc.root
>
>
> #create/update/delete elements in the root
>
> file.rewind
> formatter = REXML::Formatters::Default.new( 5 )
> formatter.write( doc, file)
> file.close
>
> end
>
> at first I was just adding and updating, and I noticed I needed to put
> the line:
> file.rewind
> or it would just append the root elements to the existing ones in the
> file, thereby creating doubles.
> Now that I have reached delete, I get the following behaviour:
>
> say the file contains:
>
> element_1
> element_2
> element_3
> element_4
>
> and I want to delete element_2, the result in the file is:
>
> element_1
> element_3
> element_4
> element_4
>
>
>
> to me, this:
> formatter.write( doc, file)
> implies that the entire xml doc would be written to the file, and as a
> result the file should only contain the doc (or the root of the doc),
> and nothing else.
>
> I am not very experienced in Ruby, and tried to resolve this way:
>
> def save
> file = File.open(@@filePath, "r+")
> doc = Document.new(file)
> root = doc.root
> file.close
>
> #create/update/delete elements in the root
>
> file = File.open(@@filePath, "w")
> formatter = REXML::Formatters::Default.new( 5 )
> formatter.write( doc, file)
> file.close
>
> end
>
>
> this works, but I feel there should be a better approach, because
> having to open the same file twice seems awkward .
>
> Thanks in advance,
IMHO you need to seek and truncate the file when opened in rw mode.
Otherwise you do not have control about where the document is written.
Since you are first reading it it is likely that the new content
simply gets appended. HTH
Kind regards
robert
--
use.inject do |as, often| as.you_can - without end