"random" and "random:" function for NSExpression's init(forFunction:arguments:)

Question

Apple's document says Function random returns

An NSNumber object (a random integer value)

After running these two line of code:

let expression = NSExpression(forFunction: "random", arguments: [])
let value: AnyObject = expression.expressionValueWithObject(nil, context: nil)

What I get is a number between 0 and 1, such as 0.312047983519733.

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As to Function random:, the document says it returns

An NSNumber object (a random integer value between 0 and the value in the array (exclusive))

I try to use it as according to document (take a parameter which is an NSArray object containing one NSExpression object representing a number):

let expression = NSExpression(forFunction: "random:", arguments: [NSExpression(forConstantValue: 100)]) // The compiler says "Execution was interrupted, reason: signal SIGABRT"
let value: AnyObject = expression.expressionValueWithObject(nil, context: nil)

The first line even cannot pass compiling. In the console, it says "Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'random: is not a supported method.'"

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I'm not sure what the problem is. I've tried all functions for init(forFunction:arguments:), all worked as described in the document except random and random:.

Answer 1

The reason this doesn't work is because there is a slight difference in the selector name between random and randomn:. Notice the n at the end of the latter.

This should work

let expression = NSExpression(forFunction: "randomn:", arguments: 
[NSExpression(forConstantValue: 100)])
let value: AnyObject = expression.expressionValueWithObject(nil, context: nil)