Spilt an NSMutableArray of NSDictionaries - ios

Question

I am trying to create a view that contains a UITableView, I would like to populate the UITableView using an NSMutableArray of NSDictionaries. I would however like to split the NSMutableArray into sections using one of the NSDictionaries key values.
The NSDictionary looks like this
First Name
Last Name
Age
The NSMutableArray is not sorted however I would like to create the UITableView that is split up into sections based on age and sorted lowest to highest.

Answer 1

NSArray has a method called sortedArrayUsingComparator:, which is called on an NSArray object and takes a block which returns as NSComparison result as an argument.
You can sort on the Age key as such:
NSArray *sortedArray = [yourArray sortedArrayUsingComparator:
^NSComparisonResult(id a, id b) {
NSInteger ageA = [[(NSDictionary*)a objectForKey:#"Age"] integerValue];
NSInteger ageB = [[(NSDictionary*)b objectForKey:#"Age"] integerValue];
if(a < b)
return NSOrderedAscending;
if(b < a)
return NSOrderedDescending;
else
return NSOrderedSame;
}];
For splitting into sections, since we've already sorted it, we can just iterate through the array:
NSMutableArray *sectionedArray = [NSMutableArray array];
for(NSDictionary *curDict in sortedArray) {
if([[curDict objectForKey:#"Age"] isEqual:
[[[sectionedArray lastObject] firstObject] objectForKey:#"Age"]) {
[[sectionedArray lastObject] addObject:curDict];
} else {
NSMutableArray *newSection = [NSMutableArray arrayWithObject:curDict];
[sectionedArray addObject:newSection];
}
}

Answer 2

First of all, you need to sort the array with this function:
self.mutableArray = [mutableArray sortedArrayUsingComparator:^NSComparisonResult(id a, id b) {
NSInteger ageA = [[(NSDictionary*)a objectForKey:#"Age"] integerValue];
NSInteger ageB = [[(NSDictionary*)b objectForKey:#"Age"] integerValue];
if(a < b) return NSOrderedAscending;
if(b < a) return NSOrderedDescending;
return NSOrderedSame;
}];
Now you can extract from the array the distinct values for the key "Age":
NSArray *uniqueAges = [_mutableArray valueForKeyPath:#"#distinctUnionOfObjects.Age"];
Finally, you can use this array to return the number of section in the tableView delegate:
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return [uniqueAges count];
}
And also you can use the array to return the name of the section:
- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section {
return [uniqueAges objectAtIndex:section];
//remember to return a string if isn't so!
}