Sorting 2-dimensional arrays - iphone

Question

I have the following case. I import data from an xml feed and from facebook graph api, in this case posts. I want to merge this data in a array and sort this on the included date data.
I have now the following:
[containerArray addObject: [NSMutableArray arrayWithObjects: created_time, message, picture, fbSource, nil ]
];
This creates a 2-dimensional array, but i want to order all the entries on created_time.
How can i best solve this problem? Thnx in advance!!

Answer 1

Create a data class containing the necessary instance variables instead of the mutable array. Then you can use the various sort method of the NSArray class, for example sortedArrayUsingDescriptors.
A sort could look like this:
NSSortDescriptor *sortDescriptor = [[[NSSortDescriptor alloc] initWithKey:#"created_time"
ascending:YES] autorelease];
NSArray *sortedArray = [containerArray sortedArrayUsingDescriptors:[NSArray arrayWithObject:sortDescriptor]];
[sortDescriptor release];
EDIT
To quote Mr. Fowler from his book Refactoring: Improving the Design of Existing Code.
Replace Array with Object
You have an array in which certain elements mean different things.
Replace the array with an object that has a field for each element
...
Motivation
Arrays are a common structure for organizing data. However, they should be used only to contain a collection of similar objects in somre order.
That's what we want to do here. Let's create a simple Posts class. You can easily add your custom initializer which accepts the four values as parameters, or even a convenience class method to return an autoreleased object later on. This is just a basic skeleton:
Post.h
#interface Posts : NSObject
{
NSDate *created_time;
NSString *message;
UIImage *picture;
id fbSource; // Don't know what type :)
}
#property (nonatomic, retain) NSDate *created_time;
#property (nonatomic, copy) NSString *message;
#property (nonatomic, retain) UIImage *picture;
#property (nonatomic, retain) id fbSource;
#end
Post.m
#import "Post.h"
#implementation Post
#synthesize created_time, message, picture, fbSource;
#pragma mark -
#pragma mark memory management
- (void)dealloc
{
[created_time release];
[message release];
[picture release];
[fbSource release];
[super dealloc];
}
#pragma mark -
#pragma mark initialization
- (id)init
{
self = [super init];
if (self) {
// do your initialization here
}
return self;
}
EDIT 2
Adding a Post object to your array:
Post *newPost = [[Post alloc] init];
newPost.reated_time = [Date date];
newPost.message = #"a message";
newPost.picture = [UIImage imageNamed:#"mypic.jpg"];
// newPost.fbSource = ???
[containerArray addObject:newPost];
[newPost release];