Array variable access problem in Objective-C

Question

I have a problem that I can't figure out even after a couple of hours of testing different ways to achieve what I need: Here is the code I have a problem with:

AppDelegate.h

#import <Three20/Three20.h>

#import "NewsRssParser.h"
#import "NewsRss.h"

@class NewsRssParser;
@class NewsRss;

@interface AppDelegate : NSObject <UIApplicationDelegate,NewsRssParserDelegate> {
 NewsRssParser * _rssParser; 
 NSMutableArray * _newsRssArray;
}

@property(readwrite, retain) NewsRssParser * rssParser;
@property(readwrite, retain) NSMutableArray * newsRssArray;

@end

AppDelegate.m

@implementation AppDelegate

@synthesize rssParser = _rssParser;
@synthesize newsRssArray = _newsRssArray;

[...]

- (void)myFunction{

 NSMutableArray *dsItems = [[[NSMutableArray alloc] init] autorelease];

 for(NSMutableArray *rssItem in self.rssParser.rssItems)
 {
  NSString * rssItemTitle = [(NewsRss *)rssItem title];
  NSString * rssItemAuthor = [@"par " stringByAppendingString:[(NewsRss *)rssItem author]];
  NSString * rssItemDescription = [(NewsRss *)rssItem description];
  NSString * rssItemLinkUrl = [(NewsRss *)rssItem linkUrl];
  NSString * rssItemImageUrl = [(NewsRss *)rssItem mediaUrl];

  TTTableMessageItem *tMsgItem = [TTTableMessageItem itemWithTitle:rssItemTitle caption:rssItemAuthor text:rssItemDescription timestamp:nil imageURL:rssItemImageUrl URL:rssItemLinkUrl];
  [self.newsRssArray addObject:tMsgItem];
  [dsItems addObject:tMsgItem];
 }

 NSLog(@"AppDelegate/count/rssItems=%d", [self.rssParser.rssItems count]);
 NSLog(@"AppDelegate/count/newsRssArray=%d", [self.newsRssArray count]);
 NSLog(@"AppDelegate/count/dsItems=%d", [dsItems count]);

}

When I run the code, my RSS parser works properly and I can loop on 10 items in self.rssParser.rssItems. I need to access these items in another view to show them in a table, hence I prepare the data in NSMutableArray * newsRssArray that I have declared in my .h file

However if I try to add those 10 objects in the NSMutableArray * newsRssArray, I have nothing in the end (see the code output in the debugger). I test my code successfully if I use NSMutableArray *dsItems declared inside my function.

Here is gdb output:

Attaching to process 47209.
2011-01-29 14:55:24.813 TestApp[47209:207] AppDelegate/count/rssItems=10
2011-01-29 14:55:24.814 TestApp[47209:207] AppDelegate/count/newsRssArray=0
2011-01-29 14:55:24.815 TestApp[47209:207] AppDelegate/count/dsItems=10
(gdb)

What am I doing wrong?

Thanks for your help!

@robin That’s the correct syntax for synthesizing a property whose name is different from the corresponding backing instance variable. — user557219
– user557219, Commented Jan 29, 2011 at 9:18
@ceyquem Why do you declare NSMutableArray *rssItem in your enumeration and repeatedly cast it to NewsRss * inside the loop? You should declare NewsRss *rssItem in your enumeration instead. — user557219
– user557219, Commented Jan 29, 2011 at 9:24
@ceyquem Paste the code where you initialise newsRssArray. If its count returns zero then the most probable cause is that you haven’t actually allocated/inited the array. — user557219
– user557219, Commented Jan 29, 2011 at 9:27
@bavarious: good point for the cast in the loop, that was an unchanged old version of the loop to be optimized, thanks — Xtophe
– Xtophe, Commented Jan 29, 2011 at 11:06
@bavarious: i am confused, newRssArray is a property of the AppDelegate, I thought it was not necessary to allocate it. Where (in which function) and how should I initialize it? — Xtophe
– Xtophe, Commented Jan 29, 2011 at 11:07

raid5ive · Accepted Answer · 2011-01-29 08:09:50Z

2

Just glancing over the code you have supplied, I don't see where you initialize newsRssArray. Is this in another place or did you forget to init?

answered Jan 29, 2011 at 8:09

raid5ive

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4 Comments

D.C. Over a year ago

I agree. use an NSLog to see if _newsRssArray is nil in your log statements.

Xtophe Over a year ago

There were 2 problems in my code: I did not declare _newsRssArray properly in the .h (missing _) and I replaced _newsRssArray by self.newsRssArray in the .m code that does not work. Both self.newsRssArray and _newsRssArray dont work.

raid5ive Over a year ago

Ah, yes. Have to be careful with small details like that :)

bshirley Over a year ago

you likely do not need to declare _newRssArray in the .h - the newer compiler will handle that for you, the property/synthesize is good enough; you absolutely should alloc/init the value at some point of initialization … [nil count] == 0

Robin · Accepted Answer · 2011-01-29 08:26:50Z

0

Just may be you are adding the items to _newsRssArray instead of newsRssArray

answered Jan 29, 2011 at 8:26

Robin

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1 Comment

Xtophe Over a year ago

There were 2 problems in my code: I did not declare _newsRssArray properly in the .h (missing _) and I replaced _newsRssArray by self.newsRssArray in the .m code that does not work. Both self.newsRssArray and _newsRssArray dont work.

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