CODEWITHSUNDEEP
objective-cxmlnsxmlparser
Luke
Luke

Reputation: 9700

Feeding XML into custom objects?

I have some XML being returned from a web query, with multiple parameters wrapped up inside a tag, like so:

<game>
    <name>First game title</name>
    <id>12345</id>
    <desc>A game..</desc>
</game>
<game>
    <name>Second game title</name>
    <id>67890</id>
    <desc>Another game..</desc>
</game>

I'm using NSXMLParser to parse it, and it's spitting out each line one by one into my console as I NSLog them. I'm trying to feed each <game> into one of my Game objects, with name as an NSString, ID as an NSNumber, etc. However, I'm struggling to work out how I'd tell it to begin a new object, since the <game> tag isn't being returned in any of my NSLog statements, only those with actual data are (such as each name, id, etc.)

If I want to get all of the data within each <game> </game> tag into a separate object, how can I do so? Here's the parser code:

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qualifiedName attributes:(NSDictionary *)attributeDict {
    element = [NSMutableString string];
}

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName {

    NSLog(@"ELEMENT TYPE: %@ VALUE: %@", elementName, element);

}

Upvotes: 1

Views: 428

Answers (1)

lukestringer90
lukestringer90

Reputation: 492

First make yourself a Game class. We will parse the XML into Games objects.

Game.h like so:

@interface Game : NSObject

@property (nonatomic, retain) NSString *name;
@property (nonatomic, retain) NSNumber *gameID;
@property (nonatomic, retain) NSString *gameDescription;

@end

Now in the class you are parsing the XML in (in this example ViewController), create a NSMutableArray property to store the Game objects as we parse them, a Game property to use as we create new Game objects, a NSString property to store the current element we are parsing in the XML, and a property for the NSXMLParser instance we are using. Also make sure it conforms to the NSXMLParserDelegate protocol.

So the header ViewController.h:

@interface ViewController : UIViewController <NSXMLParserDelegate>

@property (nonatomic, retain) NSString *currentElement;
@property (nonatomic, retain) NSMutableArray *games;
@property (nonatomic, retain) Game *gameBeingParsed;
@property (nonatomic, retain) NSXMLParser *xmlParser;

@end

Now in the implementation ViewController.m we parse the XML:

#import "ViewController.h"

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    // Make an NSMutableArray to put the parsed Game objects in
    self.games = [NSMutableArray array];

    // Get the XML data to parse
    // We need it in an NSdata object
    NSString *xmlString = @"<?xml version=\"1.0\" encoding=\"utf-8\"?><xml><game><name>First game title</name><id>12345</id><desc>A game..</desc></game><game><name>Second game title</name><id>67890</id><desc>Another game..</desc></game></xml>";
    NSData *xmlData = [xmlString dataUsingEncoding:NSStringEncodingConversionAllowLossy];

    // Set up an NSXMLParser to use
    // Set the delegate and start parsing!
    self.xmlParser = [[[NSXMLParser alloc] initWithData:xmlData] autorelease];
    _xmlParser.delegate = self;
    [_xmlParser parse];


}

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qualifiedName attributes:(NSDictionary *)attributeDict {

    // If we have a <game> tag then we are starting to parse a new Game object
    if ([elementName isEqualToString:@"game"]) {
        self.gameBeingParsed = [[[Game alloc] init] autorelease];
    }

    // If not then we need to keep track of the element name so we know which property to set on the Game object
    else {
        self.currentElement = elementName;
    }

}

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName {

    // If we have a closing </game> tag we are done parsing a Game so add it to the array
    if ([elementName isEqualToString:@"game"]) {
        [_games addObject:_gameBeingParsed];
    }
}

- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
{
    // Work out which element we have the characters for
    // Then set the property of the Game object
    if ([_currentElement isEqualToString:@"name"]){
        _gameBeingParsed.name = string;
    }
    if ([_currentElement isEqualToString:@"id"]){
        _gameBeingParsed.gameID = [NSNumber numberWithInt:[string intValue]];
    }
    if ([_currentElement isEqualToString:@"name"]){
        _gameBeingParsed.gameDescription = string;
    }
}

- (void)parserDidEndDocument:(NSXMLParser *)parser{

    // We are done parsing XML
    NSLog(@"Parsed %d Games", _games.count);
    for (Game *game in _games) {
        NSLog(@"%@ : %@ : %@", game.name, game.gameID, game.gameDescription);
    }
}

After parsing has finished and we get a call back in parserDidEndDocument: At this point the _games property will be populated we instances of Games.

Upvotes: 2

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