NSDecimalNumber lulz

rdar-20211159.playground

/*
 Fun with NSNumber to integer and unsigned integer conversions! This
 bit someone trying to use key-value coding to get the average of a
 given number out of an array of items with an NSUInteger property.

 The NSNumber which came out of the @avg.value KVC method was of value
 588.33333333333333333333333333333333333. The person then tried to access
 this value by calling both average.integerValue and
 average.unsignedIntegerValue.

 On this person's computer, which was running Mavericks, the average
 integer would be 588. On my computer, running Yosemite, the average
 would be zero. After quite a bit of futzing about, we discovered
 the following behaviors in NSNumber and NSDecimalNumber when
 converting to an integerValue or an unsignedIntegerValue.

 TL;DR - There's something screwy about how an NSDecimalNumber created
 from a string responds to being converted to an integer if the decimal is
 of sufficient length.
 */


import Cocoa


/*
 Created from an NSNumber where a float is passed in
 OSX 10.10.2, Xcode 6.2 (6C131e): 588
 OSX 10.9.5, Xcode 6.1.1 (6A2008a): 588
 */
let numberFromFloat = NSNumber(float: 588.33333333333333333333333333333333333)
numberFromFloat.integerValue
numberFromFloat.unsignedIntegerValue

/*
 Created from an NSDecimalNumber where a float is passed in.
 OSX 10.10.2, Xcode 6.2: 588
 OSX 10.9., Xcode 6.1 (6A2008a): 588
 */
let decimalNumberFromFloat = NSDecimalNumber(float: 588.33333333333333333333333333)
decimalNumberFromFloat.integerValue
decimalNumberFromFloat.unsignedIntegerValue

/*
 Created from NSDecimalNumber where a String is passed in
 OSX 10.10.2, Xcode 6.2: 0 <--- (╯°□°）╯︵ ┻━┻
 OSX 10.9., Xcode 6.1 (6A2008a): 588
 */
let decimalNumberFromString = NSDecimalNumber(string: "588.33333333333333333333333333")
decimalNumberFromString.integerValue
decimalNumberFromString.unsignedIntegerValue

/*
 Created from NSDecimalNumber where a String is passed in
 OSX 10.10.2, Xcode 6.2: 5
 OSX 10.9., Xcode 6.1 (6A2008a): 5
 */
let smallerDecimalNumberFromString = NSDecimalNumber(string: "5.3")
smallerDecimalNumberFromString.integerValue
smallerDecimalNumberFromString.unsignedIntegerValue