Mapping XML to objects using NSXMLParser (http://themainthread.com/blog/2014/04/mapping-xml-to-objects-with-nsxmlparser.html)

XMLObjectMapper.h

//
//  XMLObjectMapper.h
//  Copyright (c) 2014 Justin Driscoll All rights reserved.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

#import <Foundation/Foundation.h>

@class XMLObjectMapper;


@protocol XMLMappedObject
- (void)mapper:(XMLObjectMapper *)mapper foundString:(NSString *)string forElementNamed:(NSString *)elementName;
@end


@protocol XMLObjectMapperDelegate
- (id <XMLMappedObject>)mapper:(XMLObjectMapper *)mapper startElementNamed:(NSString *)elementName withAttributes:(NSDictionary *)attributes currentObject:(id <XMLMappedObject>)currentObject;
- (void)mapper:(XMLObjectMapper *)mapper endElementNamed:(NSString *)elementName currentObject:(id <XMLMappedObject>)currentObject;
@end


@interface XMLObjectMapper : NSObject

@property (nonatomic, weak) id <XMLObjectMapperDelegate> delegate;

- (id)initWithData:(NSData *)XMLData delegate:(id <XMLObjectMapperDelegate>)delegate;
- (void)mapElementsToObjects;
- (BOOL)inElements:(NSArray *)elementsToCheck;

@end

XMLObjectMapper.m

//
//  XMLObjectMapper.m
//  Copyright (c) 2014 Justin Driscoll All rights reserved.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

#import "XMLObjectMapper.h"


static inline NSString *strip(NSString *string) {
    return [string stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
}


@interface XMLObjectMapper () <NSXMLParserDelegate>
@property (nonatomic, strong) NSXMLParser *parser;
@property (nonatomic, strong) NSMutableArray *elements;
@property (nonatomic, strong) NSMutableArray *objects;
@property (nonatomic, strong) NSMutableString *characters;
@end


@implementation XMLObjectMapper

- (id)initWithData:(NSData *)XMLData delegate:(id <XMLObjectMapperDelegate>)delegate
{
    self = [super init];
    if (self) {
        _parser = [[NSXMLParser alloc] initWithData:XMLData];
        _parser.delegate = self;
        _delegate = delegate;
    }
    return self;
}

- (void)mapElementsToObjects
{
    _elements = [NSMutableArray array];
    _objects = [NSMutableArray array];

    [_parser parse];
}

- (BOOL)inElements:(NSArray *)elementsToCheck
{
    NSUInteger index = 0;
    for (NSString *elementToFind in elementsToCheck) {
        NSUInteger i = [self.elements indexOfObject:elementToFind];
        if (i == NSNotFound || i < index) {
            return NO;
        }
        index = i;
    }
    return YES;
}

- (void)clearString
{
    self.characters = nil;
}

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict
{
    [self.elements addObject:elementName];

    id <XMLMappedObject> object = [self.delegate mapper:self startElementNamed:elementName withAttributes:attributeDict currentObject:[self.objects lastObject]];

    if (object) {
        [self.objects addObject:object];
    }
}

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName
{
    NSAssert([[self.elements lastObject] isEqualToString:elementName], @"Attempt to end tag other than the current head.");

    [self.elements removeLastObject];

    id <XMLMappedObject> currentObject = [self.objects lastObject];

    NSString *str = strip(self.characters);
    if (str && [str length]) {
        [currentObject mapper:self foundString:str forElementNamed:elementName];
    }

    [self clearString];
    [self.objects removeLastObject];

    [self.delegate mapper:self endElementNamed:elementName currentObject:currentObject];
}

- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
{
    if (!_characters) {
        _characters = [[NSMutableString alloc] init];
    }

    [_characters appendString:string];
}

- (void)parser:(NSXMLParser *)parser foundCDATA:(NSData *)CDATABlock
{
    NSString *string = [[NSString alloc] initWithData:CDATABlock encoding:NSUTF8StringEncoding];
    [self parser:parser foundCharacters:string];
}

@end

This is great, thanks!

Hi Justin,
Can you provide a simple example on how to use this class?
Regard,
Haris

Please create a sample project for your code.
Thanks.

Same with the above two comments. Looks really good but can't quite figure out how to use it!

Tried to use it for XML with nested objects, Didn't got any success so far. Will it work for xml with nested objects?

To everyone asking for some example, the author wrote an article on this mapper: http://themainthread.com/blog/2014/04/mapping-xml-to-objects-with-nsxmlparser.html. In fact, the url is in the title :)

Hope this helps!