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iOS

Posted by Mehrbod Nikbakhsh
Mehrbod Nikbakhsh
293 Points

NSMutableArray & NSDictionary

I'm trying to build a simple App (tableview based) for reading posts (with a "load more button" ) from my back-end (PHP/MySQL) system.

  • Data I receive is in JSON . like {posts:[{ "title" : "-","time":"-"},{ "title" : "-","time":"-"}]}

  • I put it in to a NSDictionary

  • I put the "posts" part of the Dictionary into the NSMutableArray.

  • the I refresh my tableview

I have problem to add more JSON data to my table. any idea how I can solve this??

thanks

4 Answers

John W
John W
21,558 Points

I assumed your currentPosts was an NSDictionary as you initially described. Here is how the implementation would look like given your property declaration. Notice that now I'm simply referring to what used to be `currentPosts[@"posts"] with the property dot-notation self.posts. Also, the initialization should happen only once, so you should have it in viewDidLoad or lazily in the getter.

/*
In viewDidLoad
*/
self.posts = [NSMutableArray arrayWithCapacity:0];


/*
When you are loading in posts
*/
NSError * error;
// You want to do the following asynchronously, but I'm simplifying here
NSData * data = [NSData dataWithContentsOfURL:[NSURL URLWithString:@"http://yourserver.com/service.php?q=etc"] ];
NSDictionary * newPosts = [NSJSONSerialization JSONObjectWithData:data  options:0 error:&error];
if (!error) {
    [self.posts addObjectsFromArray:newPosts[@"posts"]];
}
John W
John W
21,558 Points
John W
John W
21,558 Points

The following might work. Haven't tested out myself yet, but basically I would just use addObjectsFromArray: from the NSMutableArray class to add the serialized JSON dictionary's posts element to the currentPosts dictionary's posts element.

// initialize currentPosts as follow or something similar:
NSDictionary * currentPosts = @{  @"posts": [NSMutableArray arrayWithCapacity:0] };
/*
 * A little bit down the road...
*/
NSError * error;
// You want to do the following asynchronously, but I'm simplifying here
NSData * data = [NSData dataWithContentsOfURL:[NSURL URLWithString:@"http://yourserver.com/service.php?q=etc"] ];
NSDictionary * newPosts = [NSJSONSerialization JSONObjectWithData:data  options:0 error:&error];
if (!error) {
    [currentPosts[@"posts"] addObjectsFromArray:newPosts[@"posts"]];
}
Mehrbod Nikbakhsh
Mehrbod Nikbakhsh
293 Points
Mehrbod Nikbakhsh
Mehrbod Nikbakhsh
293 Points

thanks a lot !

the code works fine at first, but not when I try to load more data and add to the currentPost. And I think it has to do with my initialization of current posts.

my NSMutableArray is an property in the [.h] file => @property (strong, nonatomic) NSMutableArray *posts; I tried to it into your first line of code , initialize it "NSDictionary * currentPosts = @{ @"posts": [self.posts arrayWithCapacity:0] };"

but it's not correct! how can I fix it?

thanks

Mehrbod Nikbakhsh
Mehrbod Nikbakhsh
293 Points
Mehrbod Nikbakhsh
Mehrbod Nikbakhsh
293 Points

fantastic.. and NOW IT WORKS .. finally after 1 weak try and error!

thank you very much John. appreciate it a lot ;)