﻿NSNumber *number1 = [NSNumber numberWithInteger:20];
NSNumber *number2 = [NSNumber numberWithInteger:40];
NSArray *numberArray = [NSArray arrayWithObjects: number1, number2, nil];

NSExpression *arrayExpression = [NSExpression expressionForConstantValue: numberArray];
NSArray *argumentArray = [NSArray arrayWithObject: arrayExpression];

NSExpression* expression =
    [NSExpression expressionForFunction:@"sum:" arguments:argumentArray];
id result = [expression expressionValueWithObject: nil context: nil];

BOOL ok = [result isEqual: [NSNumber numberWithInt: 60]]; // ok == YES