I have a plist and i want to convert it to xml. The xml itself is going to be around 1.2mb in size. What the best way to generate this xml? Simply with a NSMutableString? I am just worried about the performance issues and wether there is a better way to generate xml.
Thanks
For those wondering, what I have right now is something like this:
NSString *xml = [NSString stringWithFormat:#"<Sheet>%#</Sheet>", [self getSheetXMLString]];
and then, in getSheetXMLString method, i have more methods like above which drill down deep until the plist is fully transversed.
Thanks again.
What do you plan to do with the XML, if it is to output over a network or write to a file then instead of creating a NSString you could just write straight out to the network/file. If you plan to do manipulation if the XML you may want to consider libxml2, which is a C library included in iOS.
Related
How does NSArchiver serialize to file? I assume it's serialized in binary format, is that correct? What if I want to store it in string so I can store into SQLite database? Do I need to write my own custom NSArchiver? If so, how do I go about doing that? Are there any tutorials out there?
p.s. I do realize Core Data can do this but let me cross that option out for now.
You can archive to an NSData object instead of to a file, if you want, with +archivedDataWithRootObject:. It won't be a "string," but that's fine, because an NSString in Cocoa represents a sequence of Unicode characters, while an NSData represents a sequence of bytes (which you could easily store wherever you want, including in a database).
Note that you really should be using NSKeyedArchiver instead:
+ (NSData *)archivedDataWithRootObject:(id)rootObject
+ (id)unarchiveObjectWithData:(NSData *)data
I use a "get" request to receive a list of a data from a server. I have all of the NSURLConnection stuff working and receive the data ok. I am running into trouble actually parsing the data.
When the data is returned it is in a format like so:
[{"item":{"name":"xxx", "address":"xxx"}, "url":"xxx", "message":"xxx"}, {"item":{"name":"xxx", "address":"xxx"}, "url":"xxx", "message":"xxx"}.....]
Right now I have tried setting up the response data as an NSXMLDocument, then setting up this:
NSString *xpathQueryString =
#"";
NSArray *newItemsNodes = [rootNode nodesForXPath:xpathQueryString error:&error];
to get the nodes and parse through. But it does not work :(
I am not sure if this is the best way to go about this or if maybe my xpathQueryString is wrong.
Any help would be very much appreciated! Thank you for your time.
The text you are receiving is formatted as JSON, so you need to you a JSON Parser, rather than an XML Parser.
In iOS 5 there is a JSON parser included (NSJSONSerialisation), but if you are targeting systems running less than iOS 5, you need to use an external parser, such as JSONKit. Although JSONKit is actually more efficient than the one included in iOS5, so you're better off using it no matter what.
I want to read a list of integers from a text file, I just want to write code like
int temp;
fin>>temp;
But when I read the Cocoa documentation, I found NSFileHandle is suggested, and there is no method like I assumed, only one related method:
- (NSData *)readDataOfLength:(NSUInteger)length
Is there any class/method can help me do this in Objective C? Thanks.
I want to read a list of integers from a text file, I just want to
write code like
int temp; fin>>temp;
You have a lot of choices for file access. If you want to use C++-style access, you can, but you naturally need to open the file using the appropriate C++ file or stream methods. If you use Objective-C++, though, you can easily mix C++ code into your Objective-C.
You can also use the C standard library file routines like fopen(), fread(), etc.
Using C or C++ to read files is often a good choice if the files are coming from a source other than your program, something beyond your control.
But when I read Cocoa document, I found NSFileHandle is suggested, and
there is no method like I assumed, only one related method:
Again, lots of choices. Yes, you can use NSFileHandle to read bytes from the file into a NSData object, and then you can get ranges of bytes out of the data object. A much more common way to write and read data, though, is to use NSKeyedArchiver and NSKeyedUnarchiver:
NSData *data = [NSData dataWithContentsOfFile:pathToFile];
NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
int age = [unarchiver decodeIntForKey:#"Age"];
int weight = [unarchiver decodeIntForKey:#"Weight"];
NSString *name = [unarchiver decodeObjectForKey:#"Name"];
That's just the tip of the iceberg, though. It seems like a lot of code compared to what you were looking for, but it can also be a lot less work. Because objects and their relationships can be stored and read, you can read in a complex graph of objects with very little code:
OrgChart *chart = [NSUnarchiver unarchiveObjectWithFile:pathToFile];
Another option is to use property lists, which are very easy to use, but limited in the data types that can be used.
If you want to learn more about these topics, read Archives and Serializations Programming Guide, Property List Programming Guide, and File System Programming Guide.
You could use Objective-C++ and iostreams as you're used to.
You could use the C I/O functions like fopen and fscanf. (Probably what I'd do.)
Apple provides NSScanner for parsing, but it only reads from a string, not from an input stream. If you really want to use it, first you'll have to read your whole file (or a large chunk) into an NSString (or an NSData and then convert that to NSString).
If you can require the text file to be in JSON format, you can read it in one gulp and use NSJSONSerialization to parse it.
I need to read a HTML file and search for some tags in it. Based on the results, some tags would need to be removed, other ones changed and maybe refining some attributes — to then write the file back.
Is NSXMLDocument the way to go? I don't think that a parser is really needed in this case, it could even mean more work. And I don't want to touch the entire file, all I need to do is to load the file in memory, change some things, and save it again.
Note that, I'll be dealing with HTML, and not XHTML. Could that be a problem for NSXMLDocument? Maybe some unmatched tags or un-closed ones could make it stop working.
NSXMLDocument is the way to go. That way you can use Xpath/Xquery to find the tags you want. Bad HTML might be a problem but you can set NSXMLDocumentTidyHTML and it should be OK unless it's really bad.
NSRange startRange = [string rangeOfString:#"<htmlTag>"];
NSRange endRange = [string rangeOfString:#"</htmlTag>"];
NSString *subStr = [string subStringWithRange:NSMakeRange(startRange.location+startRange.length, endRange.location-startRange.location-startRange.length)];
NSString *finalStr = [string stringByReplacingOccurencesOfString:substr];
and then write finalstr to the file.
This is what I would do, note that I don't exactly know what the advantages of using NSXMLDocument would be, this should do it perfectly.
NSXMLDocument will possibly fail, due to the fact that HTML pages are not well formed, but you can try with NSXMLDocumentTidyHTML/NSXMLDocumentTidyXML (you can use them both to improve results) as outlined here and also have a look a this for tan approach at modifying the HTML.
I have a sample set of XML returned back:
<rsp stat="ok">
<site>
<id>1234</id>
<name>testAddress</name>
<hostname>anotherName</hostname>
...
</site>
<site>
<id>56789</id>
<name>ba</name>
<hostname>alphatest</hostname>
...
</site>
</rsp>
I want to extract everything within <name></name> but not the tags themselves, and to have that only for the first instance (or based on some other test select which item).
Is this possible with regex?
<disclaimer>I don't use Objective-C</disclaimer>
You should be using an XML parser, not regexes. XML is not a regular language, hence not easely parseable by a regular expression. Don't do it.
Never use regular expressions or basic string parsing to process XML. Every language in common usage right now has perfectly good XML support. XML is a deceptively complex standard and it's unlikely your code will be correct in the sense that it will properly parse all well-formed XML input, and even it if does, you're wasting your time because (as just mentioned) every language in common usage has XML support. It is unprofessional to use regular expressions to parse XML.
You could use Expat, with has Objective C bindings.
Apple's options are:
The CF xml parser
The tree based Cocoa parser (10.4 only)
Without knowing your language or environment, here are some perl expressions. Hopefully it will give you the right idea for your application.
Your regular expression to capture the text content of a tag would look something like this:
m/>([^<]*)</
This will capture the content in each tag. You will have to loop on the match to extract all content. Note that this does not account for self-terminated tags. You would need a regex engine with negative lookbehinds to accomplish that. Without knowing your environment, it's hard to say if it would be supported.
You could also just strip all tags from your source using something like:
s/<[^>]*>//g
Also depending on your environment, if you can use an XML-parsing library, it will make your life much easier. After all, by taking the regex approach, you lose everything that XML really offers you (structured data, context awareness, etc).
The best tool for this kind of task is XPath.
NSURL *rspURL = [NSURL fileURLWithPath:[#"~/rsp.xml" stringByExpandingTildeInPath]];
NSXMLDocument *document = [[[NSXMLDocument alloc] initWithContentsOfURL:rspURL options:NSXMLNodeOptionsNone error:NULL] autorelease];
NSArray *nodes = [document nodesForXPath:#"/rsp/site[1]/name" error:NULL];
NSString *name = [nodes count] > 0 ? [[nodes objectAtIndex:0] stringValue] : nil;
If you want the name of the site which has id 56789, use this XPath: /rsp/site[id='56789']/name instead. I suggest you read W3Schools XPath tutorial for a quick overview of the XPath syntax.
As others say, you should really be using NSXMLParser for this sort of thing.
HOWEVER, if you only need to extract the stuff in the name tags, then RegexKitLite can do it quite easily:
NSString * xmlString = ...;
NSArray * captures = [xmlString arrayOfCaptureComponentsMatchedByRegex:#"<name>(.*?)</name>"];
for (NSArray * captureGroup in captures) {
NSLog(#"Name: %#", [captureGroup objectAtIndex:1];
}
Careful about namespaces:
<prefix:name xmlns:prefix="">testAddress</prefix:name>
is equivalent XML that will break regexp based code. For XML, use an XML parser. XPath is your friend for things like this. The XPath code below will return a sequence of strings with the info you want:
./rsp/site/name/text()
Cocoa has NSXML support for XPath.