NSString Converting into a doubleValue after extracting NSString from UIPicker

I have :

    NSInteger dollarrow = [ValuesPicker selectedRowInComponent:kDollar];

    NSString *dollar = [dollarlist objectAtIndex:dollarrow];

   double converteddollar=0;

I want to do a for开发者_运维问答 loop on this and get the value in double , I am trying this :

    for(dollar=1;dollar<=99;dollar++)
    {
    converteddollar = converteddollar + 2;
    }

Now the dollar contains NSString how do I convert into double to do the operation successfully and then

NSString *message = [[NSString alloc] initWithFormat:@"%0.2f",converteddollar];

I am getting warnings and the app is crashing .. How can I correct it . I am learning Objective C please help . Thankyou . Sorry I did not want == i just wanted to use =

Your for loop is wrong. Are you really want '=='? I guess you want only '='. Can't you use something like this? (I'm just giving an example to point the mistakes in loop. Your requirement may be something different. And also I have not compiled the code, don't have mac with me right now. So you may get some minor mistake)

double sum = 0

for (NSInteger i = 1; i <= 99; i++) {
    sum += 2;  // or whatever you need here
}

NSString *convertedStr = [NSString stringWithFormat:@"%lf", sum];

Lots of errors...

NSInteger dollarrow = [ValuesPicker selectedRowInComponent:kDollar];

The selectedRowInComponent: method is a member method. Not a static one. You need to call it on an instance.

== is a comparison operator. What you want is certainly an assignment, with a single =sign.

You declare a pointer to a NSString object. But it's not initialized.
You should also use a temporary double variable for your loop.

I don't understand what your loop is supposed to do. Can you explain a little bit?

NSString *dollar = [dollarlist objectAtIndex:dollarrow];

double converteddollar = [dollar doubleValue]; should work (no need for you for loop)