Open Radar

 
Summary:
Instantiating more than 1 NSProgress (with progressWithTotalUnitCount:) 
between the becomeCurrentWithPendingUnitCount and resignCurrent 
does not make all instances children of the the current progress.

Steps to Reproduce:
  _mainProgress = [NSProgress progressWithTotalUnitCount:100];
    
    [_mainProgress becomeCurrentWithPendingUnitCount:100];

    for (int i=0; i<5; i++) {
        [self addChildProgress];
    }
    
    [_mainProgress resignCurrent];

Expected Results:
expected _mainProgress to have 5 children like in iOS 8 

<NSProgress: 0x7fe05248c750> : Parent: 0x0 / Fraction completed: 0.0000 / Completed: 0 of 100  
  <_NSProgressGroup: 0x7fe05248fcc0> : Portion of parent: 100 Children: 5
    <NSProgress: 0x7fe052519bf0> : Parent: 0x7fe05248c750 / Fraction completed: 0.0000 / Completed: 0 of 0  
    <NSProgress: 0x7fe05248fe50> : Parent: 0x7fe05248c750 / Fraction completed: 0.0000 / Completed: 0 of 0  
    <NSProgress: 0x7fe0524904e0> : Parent: 0x7fe05248c750 / Fraction completed: 0.0000 / Completed: 0 of 0  
    <NSProgress: 0x7fe052519a50> : Parent: 0x7fe05248c750 / Fraction completed: 0.0000 / Completed: 0 of 0  
    <NSProgress: 0x7fe052490070> : Parent: 0x7fe05248c750 / Fraction completed: 0.0000 / Completed: 0 of 0  


Actual Results:
same code on iOS 9.1 the main progress has only 1 child
<NSProgress: 0x7fa259d3d180> : Parent: 0x0 / Fraction completed: 0.0000 / Completed: 0 of 100  
  <NSProgress: 0x7fa259d406f0> : Parent: 0x7fa259d3d180 / Fraction completed: 0.0000 / Completed: 0 of 0 

all other 4 progress instances have the parent nil 

Version:
with iOS 8.4 an iOS 9.1

Notes:
Even though [NSProgress currentProgress] is always returning the _mainProgress as expected, using the - (instancetype)initWithParent:(NSProgress *)parentProgressOrNil userInfo:(NSDictionary *)userInfoOrNil
method and passing the [NSProgress currentProgress] the resulting progress still has the parent nil

Configuration:
iPhone 6 Simulator