UITableview, NSArrays and NSDictionnaries // Ordering - ios

Question

I have to UITableview, section headers titles contained in a dictionnary, contents in an array associated with each title (those arrays create the cells).
It is ok that many have answered here about ordering dictionnary, that is was pretty difficult, etc…
Even if a dictionnary can('t, or with difficulties) be ordered, how does it keeps the same order everytime ?
example
Let's say i end up with a table view with two sections (titled), each containing some cells
A dictionnary is declared, it contains the section titles.
NSMutableDictionary *menuEntries;
For each of those dictionnary entries, a different array associated (which then is used to create and populate the cells). We will have two sections (so two keys in the dictionnary), for some reasons we use two different array that we are going to associate to those keys
NSArray *mainMenuArray;
NSMutableArray *magazineMenuArray;
The first one is populated like this (
mainMenuArray = [[NSArray alloc] initWithObjects: btn1,btn2,btn3,btn4,nil];
The second array (magazineMenuArray) is populated via some json call (not showing here how, but everythings works fine)
So we end up up setting the dictionnary
menuEntries = [[NSMutableDictionary alloc] init];
[menuEntries setObject:mainMenuArray forKey:#"First section"];
[menuEntries setObject:self.magazineMenuArray forKey:#"Second section"];
In the end, it works pretty well, we have defined some attributes for the arrays' object, one for the title, one for the action to be called, pretty cool.
!! BUT !!
Second section appears before first section. Nothing to do about/against it. Always.
I can hear that a NSDictionnary CAN'T BE ORDERED, ok, but I reeeeeeally feel like, in that case, IT IS ORDERED somehow.
That is very confusing.

Answer 1

NSDictionary keeps the same order every time, but that is an arbitrary order based on the hash codes of the objects that you insert as keys. If the dictionary is mutable, inserting or removing objects can change the ordering of the keys that are already in the dictionary.
Although it is not possible to order the dictionary itself, it is certainly possible to order its keys into a separate array, and then walk that array in order, pulling the objects by key from the(unordered) dictionary.

Answer 2

Edit:
You say that you have
NSMutableDictionary *menuEntries;
Which is populated as:
menuEntries = [[NSMutableDictionary alloc] init];
[menuEntries setObject:mainMenuArray forKey:#"First section"];
[menuEntries setObject:self.magazineMenuArray forKey:#"Second section"];
If you want it to respect the order in which you populate it, you should use a NSMutableArray instead, e.g.:
NSMutableArray *menuEntries;
And then, you can populate that array with dictionary entries with, at the very least, two keys, something for the title of the section and something with the rows for that section. Thus:
menuEntries = [[NSMutableArray alloc] init];
[menuEntries addObject:[NSDictionary dictionaryWithObjectsAndKeys:
#"First section", #"title",
mainMenuArray, #"rows",
nil]];
[menuEntries addObject:[NSDictionary dictionaryWithObjectsAndKeys:
#"Second section", #"title",
self.magazineMenuArray, #"rows",
nil]];
Thus,
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return [menuEntries count];
}
- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section
{
NSDictionary *section = [menuEntries objectAtIndex:section];
return [section objectForKey:#"title"];
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
NSDictionary *section = [menuEntries objectAtIndex:section];
return [[section objectForKey:#"rows"] count];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
NSDictionary *section = [menuEntries objectAtIndex:indexPath.section];
NSArray *rows = [section objectForKey:#"rows"];
id row = [rows objectAtIndex:indexPath.row];
// I didn't know how mainMenuArray and self.magazineMenuArray were populated,
// so I used a data type of `id` for the row, but you can obviously replace
// that with whatever is appropriate, e.g., NSDictionary* or whatever.
// proceed with the configuring of the cell here
}
Personally, I wouldn't use the literal strings #"title" and #"rows" all over the place, but rather define constants like the following, include these at the start of the implementation, and use them instead of the literal strings. But I'm sure you get the basic idea.
NSString * const kTableTitleKey = #"title";
NSString * const kTableRowsKey = #"rows";
Regardless, this outlines a very common data model I use behind my UITableView objects. It's a nice logical structure that corresponds to the table view itself. Essentially it is an array of sections, each of which is a dictionary with two keys, one for the title and one for the rows of the section. The value for that "rows of the section" is, itself, an array, one entry for every row of the table. It sounds complicated, but as you see above, it actually makes the implementation very, very simple.
My original answer was provided before OP supplied any information about the nature of the data structures. Thus I provided an answer to the more abstract question of how does one sort an array of dictionary entries. I retain that answer for historical reference, though:
Original answer:
I'm not sure how you are storing your dictionary and how you represent rows in your table, but a common pattern is to have an array of dictionary items:
NSArray *array = #[
#{#"id" : #"1", #"name":#"Mo", #"age":#25},
#{#"id" : #"2", #"name":#"Larry", #"age":#29},
#{#"id" : #"3", #"name":#"Curly", #"age":#27},
#{#"id" : #"4", #"name":#"Shemp", #"age":#28}
];
You can then sort that via name, like so:
NSSortDescriptor *descriptor = [[NSSortDescriptor alloc] initWithKey:#"name"
ascending:YES];
NSArray *sortedArray = [array sortedArrayUsingDescriptors:#[descriptor]];
NSLog(#"array = %#", array);
NSLog(#"sortedArray = %#", sortedArray);
There are a whole series of sorting methods, so check out Sorting in the NSArray Class Reference.