Hi,
Apologies in advance, as I believe this may be a very basic question, but I've
only recently started using the Cocoa XML classes. I'm using NSXMLDocument,
NSXMLNode and NSXMLElement to read and write OPML files. Everything works fine
except for one thing - I can't seem to find a way of preserving whitespace
inside the element attribute stringValues. I've searched the docs and Googled
around for anything on whitespace or newlines and the various NSXML... classes
as I figured this would be fairly trivial, but I must be using the wrong search
terms because I can't find an obvious solution.
For instance, an .opml XML file might look like this:
<?xml version="1.0" encoding="UTF-8"?>
<opml version="1.0">
<head>
<title>Test</title>
</head>
<body>
<outline text="An item" _note="This note...
has some...
newlines...
and a tab !">
</outline>
</body>
</opml>
That is, the "_note" attribute of the <outline> element may have some newlines
and tabs in its stringValue.
I believe that whitespace like this isn't entirely supported by XML, in that
multiple whitespace characters may just get rolled back into a single space
when read back in... Certainly, that's what I'm seeing. When I read the above
OPML file in and call -stringValue on the attribute named "_note" of the
<outline> NSXMLElement, this is what I get:
This note... has some... newlines... and a tab !
In other words, all of the whitespace characters between other characters get
converted to a single space, so that I've lost line breaks and tabs.
It seems that some other OPML exporters convert newline characters to at
least (though they seem to leave tabs as-is). But I'm not sure how I would go
about that (I see that & and others are mentioned under
-predefinedEntityDeclarationForName: of the NSXMLDTD documentation, but I
cannot find much information on what that does. I have noticed that ampersands
are converted to & when an NSXMLElement is written out to file via
NSXMLDocument's -XMLData method, as are certain other characters mentioned
there (though, notably, whilst "<" became < ">" did *not* become &rt; but
remained as-is). I can't find how to convert newlines to , though. I
thought I could do it using -stringByReplacingOccurrencesOfString:, but the
NSXML... methods convert ampersands internally which prevents me from doing
this (if I could prevent "&" from becoming "&" and handle that manually
instead via -stringByReplacingOccurrencesOfString: I would at least be
able to replace newlines with " "...).
(On a sidenote, it seems that NSXMLDocument also converts " " to single
spaces internally upon reading a file before I can look for this tag...)
So, to get to the point: how can I make sure that the NSXMLElements created
from a file read using NSXMLDocument keep the whitespace intact in -stringValue
of the element's attributes? (I'm using initWithData:options:error:, and none
of the options I've tried seem to make a difference.) How can I have it so that
if I do this:
NSXMLElement *OPMLElement = ...
NSString *string = [[OPMLElement attributeForName:@"_note"] stringValue];
string may contain newlines or tab characters that haven't been squashed into
single space characters by the NSXMLDocument parsing process...
Many thanks in advance for any help.
All the best,
Keith
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