Sorting through an array objects to find the highest number

Question

I'm trying to sort through an array of objects to find the highest number. I'm fairly new with objective C (and C in general), so I am not sure why this isn't working, although my gut says its probably due to the NSNumber declaration. The max variable is always returned as random value from the array. Any ideas?

 NSNumber * max = 0;

    for (int i=0; i<mutableChartData.count; i++) {



     if ([mutableChartData objectAtIndex:i] > max) {
            max =[mutableChartData objectAtIndex:i];

        }


    }

check this [link](http://stackoverflow.com/questions/3080540/finding-maximum-numeric-value-in-nsarray) — Pawan Rai, Sep 03 '14 at 11:40
The reason your code isn't working is that you're comparing the entries in the array incorrectly. Objective-C collection classes can only store objects e.g. NSObject descendants such as NSNumber - which it looks like you're using here. Object variables e.g. your max variable are pointers, not actual objects. Therefore, when you look at the value of max you wont see the actual NSNumber object, instead you see a memory reference - which points to the location of the NSNumber object. — mmccomb, Sep 03 '14 at 11:58
A @mmccomb indicates, your `max` should be declared as `long` or `int` (or, perhaps, `NSInteger`) and you should do `[[mutableChartData objectAtIndex:i] longValue] > max` in your compare and assign the `longValue` to `max` if the compare is true. — Hot Licks, Sep 03 '14 at 12:05
Thank you @HotLicks, I had been trying the "longValue" stuff, but didn't quite get the syntax right with the braces. — spogebob92, Sep 03 '14 at 12:17
But this is stuff you should know. In particular, the difference between a number and a pointer is critical, and you will get into deep trouble in Objective-C if you don't clearly "get" the difference. — Hot Licks, Sep 03 '14 at 12:38
My point is that you should not attempt Objective-C programming unless you already have a good foundation in this stuff. — Hot Licks, Sep 03 '14 at 16:03

chaithraVeeresh · Answer 1 · 2014-09-03T12:11:18.280

-1

enumerate array using code below:

NSNumber *max = 0;

[mutableChartData enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *Stop)
 {
     if ([mutableChartData[i] intValue] > [max intValue]) {
        max =mutableChartData[i];
    }

 }];

enumerartion is fast and efficient and you will get maximum number in array

edited Sep 03 '14 at 12:11

answered Sep 03 '14 at 11:50

chaithraVeeresh

258
3
11

Not working I'm afraid, giving my max as "1391716256" when the max is 200. – spogebob92 Sep 03 '14 at 11:55
You make the same error as OP in his code. – Martin R Sep 03 '14 at 11:55
no it worked for me i'm initialising max = 0 and i'm enumerating through array so will get max number defined in array itself – chaithraVeeresh Sep 03 '14 at 11:58
to get max number in an array it is the eficient method i think – chaithraVeeresh Sep 03 '14 at 12:03
1

@chaithraVeeresh: Have a look at mmccomb's comment above, and at the duplicate question that I pointed to. You cannot compare NSNumber objects with `<` because that compares the pointers, not the values. – Martin R Sep 03 '14 at 12:05
@MartinR ok i got it. we can compare by intValues of an array so it will compare values but not pointers i guess – chaithraVeeresh Sep 03 '14 at 12:12

Sorting through an array objects to find the highest number

1 Answers1