How do I get Scientific Notation in a text field?

Question

I'm trying to get this text field in my app to display in scientific notation after 8 characters are entered in (sort of like the built-in Calculator App). I've got everything working right, except when it's supposed to show in scientific notation, it just shows '0.0'.

What is wrong with my code?

NSString *current;
NSString *str = (NSString*)[sender currentTitle]; //sender is in the method header
if([current isEqualToString:@"0"]) {
    current = str;
} else if (current.length < 8){
    current = [current stringByAppendingString:str];
} else {
    NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
    [formatter setNumberStyle:NSNumberFormatterScientificStyle];
    current = [formatter stringFromNumber:(NSNumber*)current];
}

score 1 · Accepted Answer · edited May 23 '17 at 12:28

1

You can't just cast an NSString to an NSNumber. Use doubleValue to convert an NSString to a double:

current = [formatter stringFromNumber:@([current doubleValue])];

Or you can use an NSNumberFormatter to convert strings to numbers as described in this answer

edited May 23 '17 at 12:28

Community

1
1

answered Mar 26 '13 at 03:15

Sebastian

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Now, using the code you gave me, nothing happens after 8 characters are inserted. – cory ginsberg Mar 26 '13 at 03:47
1

If you step through the code with the debugger, do you end up in the final `else` block? – Sebastian Mar 26 '13 at 03:58
@coryginsberg: Check your if-statements. You probably should test `str`, not `current`. – Martin R Mar 26 '13 at 21:51

How do I get Scientific Notation in a text field?

1 Answers1