iOS objective sort dictionary by quantity

Question

I'm new to iOS development, and I'm in problem that I don't know how to solve it...

I have JSON:

{
    "038b7af5-2874-448b-88c3-f667908723d8" = {
        Name = "Coffee";
        Quantity = 5;
    };
    "4d63daaf-962b-4382-a90e-dd4db0ce052e" = {
        Name = "Water";
        Quantity = 1;
    };
    "693a6897-4250-4eef-8164-3bb1812315fc" = {
        Name = "Fruit frappe";
        Quantity = 1;
    };
    "778a66df-a2ec-419f-b9dc-94e0c0fef40d" = {
        Name = "Fruit nes frappe";
        Quantity = 1;
    };
}

What I want to do is to sort them in UITableViewController by quantity. I tried NSSortDescriptor but with no success... Thanks in advance, Stefan

Answer 1

Dictionaries are unordered collection types.

To order the tableview you need to use an additional array (which can be ordered) of the dictionary keys.

So to populate item 0 of the tableview you get the key from the array at index 0 and then get the column values from the dictionary entry with that key.

In order to sort this array by Quanitity you do this:

@property (readonly) NSMutableArray *arrayIndex;
@property (readonly) NSMutableDictionary *dataDict;

...

[arrayIndex sortUsingComparator:^NSComparisonResult(NSString *keyA, NSString *keyB) {
    NSDictionary *dictA = _dataDict[keyA];
    NSNumber *quantityA = dictA["Quantity"];
    NSDictionary *dictB = _dataDict[keyB];
    NSNumber *quantityB = dictB["Quantity"];
    if (quantityA.integerValue > quantityB.integerValue)
        return NSOrderedDescending;
    else if (quantityA.integerValue < quantityB.integerValue)
        return NSOrderedAscending;
    return NSOrderedSame;
}];

Free tip: Don't store data in dictionaries if you can avoid it; instead convert the dictionary to a custom object as soon as possible as custom objects bring so much power and flexibility to your code, and look how much code I had to write just to make a comparator.