Wednesday, December 9, 2009

Simple Objective-XML example

Many times now, I've been asked about more Objective-XML examples. Here's a very simple one. It is adapted from Marcus Zarra's very helpful libxml and xmlreader tutorial. That tutorial shows how to parse a very simple XML format using libxml2.

The XML file parsed is the following:

<?xml version="1.0" encoding="UTF-8"?>

<root>

  <person>

    <name>John Doe</name>

    <age>14</age>

  </person>

  <person>

    <name>Mary Doe</name>

    <age>14</age>

  </person>

  <person>

    <name>John Smith</name>

    <age>15</age>

  </person>

</root>

It is parsed using at application startup using the following code:

- (void)applicationDidFinishLaunching:(NSNotification*)notification

{

NSString *path = [[NSBundle mainBundle] pathForResource:@"xmlExample" ofType:@"xml"];

NSData *xmlData = [NSData dataWithContentsOfFile:path];

xmlTextReaderPtr reader = xmlReaderForMemory([xmlData bytes],

[xmlData length], 

[path UTF8String], nil, 

(XML_PARSE_NOBLANKS | XML_PARSE_NOCDATA | XML_PARSE_NOERROR | XML_PARSE_NOWARNING));

if (!reader) {

NSLog(@"Failed to load xmlreader");

return;

}

NSString *currentTagName = nil;

NSDictionary *currentPerson = nil;

NSString *currentTagValue = nil;

NSMutableArray *people = [NSMutableArray array];

char* temp;

while (true) {

if (!xmlTextReaderRead(reader)) break;

switch (xmlTextReaderNodeType(reader)) {

case XML_READER_TYPE_ELEMENT:

//We are starting an element

temp =  (char*)xmlTextReaderConstName(reader);

currentTagName = [NSString stringWithCString:temp

encoding:NSUTF8StringEncoding];

if ([currentTagName isEqualToString:@"person"]) {

currentPerson = [NSMutableDictionary dictionary];

[people addObject:currentPerson];

}

continue;

case XML_READER_TYPE_TEXT:

//The current tag has a text value, stick it into the current person

temp = (char*)xmlTextReaderConstValue(reader);

currentTagValue = [NSString stringWithCString:temp

encoding:NSUTF8StringEncoding];

if (!currentPerson) return;

[currentPerson setValue:currentTagValue forKey:currentTagName];

currentTagValue = nil;

currentTagName = nil;

default: continue;

}

}

NSLog(@"%@:%s Final data: %@", [self class], _cmd, people);

[self setRecords:people];

}

To parse it using MAX you need to add MPWXmlKit and MPWFoundation to your project, and then replace the code above with the following:

- (void)applicationDidFinishLaunching:(NSNotification*)notification

{

NSString *path = [[NSBundle mainBundle] pathForResource:@"xmlExample" ofType:@"xml"];

NSArray *people=[[MPWMAXParser parser] parsedDataFromURL:[NSURL fileURLWithPath:path]];

[self setRecords:people];

}

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