Product/Multiplication NSMutableArray Values [clos

问题:

I have an NSMutableArray and I need to make the product of all the numbers inside it. I just can't understand how to do. PS. I'm quite new with objective-c so be as clear as possible. Thank's

回答1:

yes you can also do like this..

int result=1;
NSMutableArray *array=[[NSMutableArray alloc]initWithObjects:@"1",@"2",@"3",@"4", nil];
for (int i=0; i<[array count]; i++) {
result*=[[array objectAtIndex:i] integerValue];
}
NSLog(@"%d     ",result);

回答2:

H2CO3 is right. For the sake of completeness try

NSNumber * sum = [numArray valueForKeyPath:@"@sum.self"];

where numArray is your array.

回答3:

You can have a look on NSExpression class it's very powerfull and you can customize it to your requirements. It's also support many build in functions, for example:

NSArray *nums = @[@1, @2, @3, @4, @5];
NSExpression *expression = [NSExpression expressionForFunction:@"sum:" arguments:@[[NSExpression expressionForConstantValue:nums]]];
id result = [expression expressionValueWithObject:nil context:nil];

回答4:

Assuming we're working with int values...

int sum = 1;
for (NSNumber *num in someArray) {
    sum *= [num intValue];
}
NSLog(@"%d", sum);

int and intValue can easily be replaced with double and doubleValue or whatever is appropriate for what you need. someArray is the name of the array of values.

---

If, however... the question is poorly worded and we've all misunderstood, and you need a new array whose indices contain the product of the values of the objects at the same indices in two other arrays, then you're looking for something more like this:

NSMutableArray *productArray = [NSMutableArray array];
for(int i=0; i<[arr1 count]; ++i) {
    int product = [[arr1 objectAtIndex:i] intValue] * [[arr2 objectAtIndex:i]
        intValue];
    [productArray addObject: [NSNumber numberWithInt: product]];
}