Question

I’m writing an app for iOS and i have to read an external xml file. My program logic is working very well. I checked that several times with NSLog messages. My problem is, when I’m adding an new object to my NSMutuableArray masterNewsList then is after the insertion every object overwritten by the last inserted object. What’s my mistake here? I can’t find it.

//  NewsData.h

#import <Foundation/Foundation.h>

@interface NewsData : NSObject

@property (nonatomic,copy) NSString *title;
@property (nonatomic,copy) NSString *date;
@property (nonatomic,copy) NSString *detail;
@property (nonatomic,copy) NSString *content;

-(id) initWithTitle:(NSString *)title  date:(NSString *)date detail:(NSString *)detail content:(NSString *)content;

@end


//NewsData.m

#import "NewsData.h"

@implementation NewsData

-(id)initWithTitle:(NSString *)title date:(NSString *)date detail:(NSString *)detail content:(NSString *)content{
 self = [super init];
 if (self) {
    _title = title;
    _date = date;
    _detail = detail;
    _content = content;
    return self;
}
return nil;
}

@end



//  NewsDataController.h


#import <Foundation/Foundation.h>

@class NewsData;

@interface NewsDataController : NSObject <NSXMLParserDelegate>

@property (nonatomic, copy) NSMutableArray *masterNewsList;

- (NSUInteger)countOfList;
- (NewsData *)objectInListAtIndex:(NSUInteger)theIndex;

@end



//  NewsDataController.m


#import "NewsDataController.h"
#import "NewsData.h"

@interface NewsDataController()

@property NSMutableString *title;
@property NSMutableString *description;
@property NSMutableString *content;
@property NSMutableString *date;

@property BOOL itemValue;
@property BOOL titleValue;
@property BOOL descriptionValue;
@property BOOL contentValue;
@property BOOL dateValue;

-(void) initializeDataList;
- (void)addNewsData:(NewsData *)newsData;

@end

@implementation NewsDataController

- (void) initializeDataList {
    NSMutableArray *newsList = [NSMutableArray array];
    self.masterNewsList = newsList;

    self.title = [NSMutableString stringWithString:@""];
    self.description = [NSMutableString stringWithString:@""];
    self.content = [NSMutableString stringWithString:@""];
    self.date = [NSMutableString stringWithString:@""];

    self.itemValue = false;
    self.contentValue = false;
    self.dateValue = false;
    self.titleValue = false;
    self.descriptionValue = false;

    NSData *xmlData = nil;
    xmlData = [[NSData alloc] initWithContentsOfURL:[NSURL URLWithString:@"http://www.somesite.de/?type=100"]];
    if (xmlData != nil) {
        NSXMLParser *theParser = [[NSXMLParser alloc] initWithData:xmlData];
        theParser.delegate = self;
        [theParser parse];
    }
     else{
        NewsData *newsData;
        newsData = [[NewsData alloc] initWithTitle:@"Es konnten keine News geladen werden" date: @"---" detail:@"Keine Verbindung zum Server" content:@"Bitte Netzwerkverbindung überprüfen!"];
        [self addNewsData:newsData];
    }
}

-(void) setMasterNewsList:(NSMutableArray *)newList{
    if (_masterNewsList != newList) {
        _masterNewsList = [newList mutableCopy];
    }
}

-(id) init{
    if (self = [super init]) {
        [self initializeDataList];
        return self;
    }
    return nil;
}

- (NSUInteger) countOfList{

    return [self.masterNewsList count];
}

- (NewsData *)objectInListAtIndex:(NSUInteger)theIndex{

    return [self.masterNewsList objectAtIndex:theIndex];
}

Method who add the object to masterNewsList

- (void) addNewsData:(NewsData *)newsData{

    [self.masterNewsList addObject:newsData];

}

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

    if ([elementName isEqualToString:@"item"]) {
        self.itemValue = true;
    }
    if ([elementName isEqualToString:@"title"]) {
        [self.title deleteCharactersInRange:NSMakeRange(0, self.title.length)];
        self.titleValue = true;
    }
    if ([elementName isEqualToString:@"description"]) {
        [self.description deleteCharactersInRange:NSMakeRange(0, self.description.length)];
        self.descriptionValue = true;
    }
    if ([elementName isEqualToString:@"content:encoded"]) {
        [self.content deleteCharactersInRange:NSMakeRange(0, self.content.length)];
        self.contentValue = true;
    }
    if ([elementName isEqualToString:@"pubDate"]) {
        [self.date deleteCharactersInRange:NSMakeRange(0, self.date.length)];
        self.dateValue = true;
    }
 }

Here I’m creating the new object of kind NewsData and calling then the addNewsData Method

-(void) parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName{
    if ([elementName isEqualToString:@"item"]) {
        NewsData *newsData;
        newsData = [[NewsData alloc] initWithTitle:self.title date:self.date detail:self.description content:self.content];
        [self addNewsData:newsData];
        self.itemValue = false;
    }
    if ([elementName isEqualToString:@"title"]) {
        self.titleValue = false;
    }
    if ([elementName isEqualToString:@"description"]) {
        self.descriptionValue = false;
    }
    if ([elementName isEqualToString:@"content:encoded"]) {
        self.contentValue = false;
    }
    if ([elementName isEqualToString:@"pubDate"]) {
        self.dateValue = false;
    }
}

-(void) parser:(NSXMLParser *)parser foundCharacters:(NSString *)string{
    if (self.itemValue && self.titleValue) {
        [self.title appendString:string];
    }
    if (self.itemValue && self.descriptionValue) {
        [self.description appendString:string];
    }
    if (self.itemValue && self.contentValue) {
        [self.content appendString:string];
    }
    if (self.itemValue && self.dateValue) {
        [self.date appendString:string];
    }
}

-(void) parser:(NSXMLParser *)parser foundCDATA:(NSData *)CDATABlock{
    if (self.itemValue && self.contentValue) {
        [self.content appendString:[[NSString alloc] initWithData:CDATABlock encoding:NSUTF8StringEncoding]];
    }
}



@end

Answer 1

Your mistake is here:

if (self) {
    // None of these assignments copies the incoming mutable strings.
    // When strings change later on, so do titles, details, content, and so on.
    _title = title;
    _date = date;
    _detail = detail;
    _content = content;
    return self;
}

You are using assignments to backing variables of properties marked copy. Switch to assigning to properties, and your problem will be fixed:

if (self) {
    // Since your property is correctly marked `copy` (a good idea for NSString)
    // these assignments will make copies of mutable strings,
    // preventing the unwanted modifications.
    self.title = title;
    self.date = date;
    self.detail = detail;
    self.content = content;
    return self;
}