Getting index of minimum double value within NSMutableArray

Question

I need to get the minimum value (and its index) among objects inside an NSMutable double array.

I get the minimum value correctly but I cannot get its index. A weird and very high number comes up. How can I retrieve the index?

double lowestvalue = 1.0;
double highestvalue = 100.0;
double n4 = 4.0;
double n2 = 2.0;
double n3 = 3.0;
double n1 = 10.0;

NSMutableArray *arr1 = [[NSMutableArray alloc] init];

NSNumber *num1 = [NSNumber numberWithDouble:n1];
NSNumber *num2 = [NSNumber numberWithDouble:n2];
NSNumber *num3 = [NSNumber numberWithDouble:n3];
NSNumber *num4 = [NSNumber numberWithDouble:n4];
NSNumber *numL = [NSNumber numberWithDouble:lowestvalue];
NSNumber *numH = [NSNumber numberWithDouble:highestvalue];

[arr1 addObject:num2];
[arr1 addObject:num3];
[arr1 addObject:num4];
[arr1 addObject:numL];
[arr1 addObject:num1];
[arr1 addObject:numH];

NSLog(@"arr1: %@",arr1);

NSNumber * min_ = [arr1 valueForKeyPath:@"@min.doubleValue"];
NSString *str1_ =[NSString stringWithFormat:@"%@",min_];
NSInteger path1_ =[arr1 indexOfObject:str1_];
NSIndexPath *indepath1_ =[NSIndexPath indexPathForItem:path1_ inSection:0];

NSLog(@"Min_ Value = %f and index_ = %ld",[min_ doubleValue], (long)indepath1_.row);


//Min_ Value = 1.000000 and index_ = 9223372036854775807

CRD · Accepted Answer · 2019-08-14 17:46:31Z

0

Your "weird" number is NSNotFound, which you will find is covered in the documentation under the "Return Value" section.

The reason your object is not found is you have an array of NSNumber * references/objects, valueForKeyPath returns an NSNumber * which you store in min_, you then produce a different NSString object (effectively creating a "picture" of your NSNumber object) storing its reference in str1, and then ask indexOfObject if your new object of a different type is in your array – answer NSNotFound.

HTH

answered Aug 14, 2019 at 17:46

CRD

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6 Comments

jeddi Over a year ago

Got it. Many thanks for pointing it out. However how can I get the index of the minimum number?

CRD Over a year ago

@jeddi - lookup the object from the array, e.g. [arr1 indexOfObject:min_]

jeddi Over a year ago

It gives me exactly the same issue (NSNotFound)

jeddi Over a year ago

By the way, this is not the problem. My code works perfectly fine if the array is composed of strings, but it fails to return the index when the doubles are wrapped in NSNumbers. There must be a problem here: NSNumber *num1 = [NSNumber numberWithDouble:n1];

jeddi Over a year ago

Or the problem is the formatting of the NSLog...... NSLog(@"Min_ Value = %f and index_ = %ld",[min_ doubleValue], (long)indepath1_.row); Any idea?

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