sorting array of nested NSDictionary containing an array - iphone

Question

Im quite new to iOS and objective.. heres my question..
if my array looks like this:
myArray = {
parentdict = {
childdict = {
aname = "Aname";
bname - "Bname";
cname = "Cname";
};
childarray = {
{
counter = "1";
close = "25236";
},
{
counter = "2";
close = "12458";
};
};
};
},
{
parentdict = {
childdict = {
aname = "Aname";
bname - "Bname";
cname = "Cname";
};
childarray = {
{
counter = "1";
close = "28556";
},
{
counter = "2";
close = "12118";
};
};
};
},
{
parentdict = {
childdict = {
aname = "Aname";
bname - "Bname";
cname = "Cname";
};
childarray = {
{
counter = "1";
close = "24356";
},
{
counter = "2";
close = "155628";
};
};
};
};
basically its an array of nested dictionary and inside one of the dictionary contains an array of dictionary (childarray) if i want to sort myArray by #"close" of array index 1, which is the one next to counter 2, exactly how should i do this?..(perhaps i should use NSSortDescriptor?)
thanks for the reply

Answer 1

You have presented your structure in the JSON format. I assume it is for sake of presenting it to the audience here. If you are actually starting with JSON string, you will have to convert it to nested NSArrayies and NSDictionaryies using some third-party libs or iOS 5 built-in classes..
Assuming you already have your top level NSArray* myArray, give it a try to the following code:
NSArray* myArray = // ... this is your array
NSArray* sorted_array = [myArray sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {
NSDictionary* left = obj1;
NSDictionary* right = obj2;
NSDictionary* left_parent_dict = [left objectForKey: #"parentdict"];
NSDictionary* right_parent_dict = [right objectForKey: #"parentdict"];
NSArray* left_child_array = [left_parent_dict objectForKey: #"childarray"];
NSArray* right_child_array = [right_parent_dict objectForKey: #"childarray"];
NSDictionary* left_child_first = [left_child_array objectAtIndex: 1];
NSDictionary* right_child_first = [right_child_array objectAtIndex: 1];
NSString* left_close = [left_child_first objectForKey: #"close"];
NSString* right_close = [right_child_first objectForKey: #"close"];
NSNumber* left_val = [NSNumber numberWithInt: [left_close intValue]];
NSNumber* right_val = [NSNumber numberWithInt: [right_close intValue]];
return [left_val compare: right_val];
} ];
You will need, of course, to add some checks which I omitted for simplicity.
If you want to get descending order modify the last statement to:
return [right_val compare: left_val];
I would also suggest you considering SQL database for complex data structures as pointed out by Niko.

Answer 2

Sorting an array can be quite complex, especially when the array contains nested objects. May be you should create an SQLite database

Answer 3

You should use iOS 5.0's built in JSON API. [Here's a link to a great tutorial.] (http://www.raywenderlich.com/5492/working-with-json-in-ios-5). JSON is really easy to work with. And that site also has great tutorials on Core Data (iOS's SQLite API) here. There are two more parts to that tutorial as well.

Answer 4

Try this
[array sortUsingComparator:(NSComparator)^(id obj1, id obj2){
int firstValue = [[obj1 objectForKey:#"someKey"] intValue];
int secondValue = [[obj2 objectForKey:#"someKey"] intValue];
int valueDiff = firstValue - secondValue;
return (valueDiff == 0) ? NSOrderedSame : (valueDiff < 0) ? NSOrderedAscending : NSOrderedDescending;
}];