How to catch a Nan?

How to catch a Nan?

NaN is not equal to any value, including NaN, use this property instead of the equal-to operator (==) or not-equal-to operator (!=) to test whether a value is or is not NaN.

Nan represents Not a number

When it happens to get a Nan as a result of an expression you have to find a way to catch it before.

Let’s think an if statement and inside this the appropriate check.

A working code is the following:

Objective-C

The class property [NSDecimalNumber notANumber] is just for this purpose. In some languages NaN != NaN

if NSNumber is a NaN, convert it to a double and use the C function isnan():

NSNumber *validNumber = [NSNumber numberWithDouble: 1.];
NSLog( @"%d", isnan(validNumber.doubleValue) ); // prints "0"

NSNumber *nanNumber = [NSNumber numberWithDouble: 0./0.];
NSLog( @"%d", isnan(nanNumber.doubleValue) ); // prints "1"

[[NSDecimalNumber notANumber] isEqualToNumber:myNumber]

if ([[NSDecimalNumber decimalNumberWithString:self.price...] isEqual:[NSDecimalNumber notANumber]]) {

//Code

}

SWIFT 

let x = 0.0
let y = x * .infinity
// y is a NaN

// Comparing with the equal-to operator never returns 'true'
print(x == Double.nan)
// Prints "false"
print(y == Double.nan)
// Prints "false"

// Test with the 'isNaN' property instead
print(x.isNaN)
// Prints "false"
print(y.isNaN)
// Prints "true"