如何找出NSString中是否有“。”？

Question

Have got an

NSString *str = @"12345.6789"

and want to find out if there is that "." character inside of it. I'm afraid that there are ugly char-encoding issues when I would just try to match an @"." against this? How would you do it to make sure it always finds a match if there is one?

I just need to know that there is a dot in there. Everything else doesn't matter.

Answer 1

You can use rangeOfString: message to get the range where your "." is.

The prototype is:

- (NSRange)rangeOfString:(NSString *)aString

You can find more info about this message in: Mac Dev Center

There would be something like this:

NSRange range;  
range = [yourstring rangeOfString:@"."]; 
NSLog(@"Position:%d", range.location);

If you need to, there is another message ( rangeOfString:options: ) where you can add some options like "Case sensitive" and so on.

Answer 2

If [str rangeOfString:@"."] returns anything else than {NSNotFound, 0} , the search string was found in the receiver. There are no encoding issues as NSString takes care of encoding. However, there might be issues if your str is user-provided and could contain a different decimal separator (eg, a comma). But then, if str really comes from the user, many other things could go wrong with that comparison anyway.

Answer 3

To check . symbol, it will be useful.

if ([[str componentsSeparatedByString:@"."] count]>1) {
        NSLog(@"dot is there");
}else{
        NSLog(@"dot is not there");
}

Answer 4

If what you really want to do is determine whether the string represents a number with a fractional part, a better solution is to feed the string to a number formatter, then examine the number's doubleValue to see whether it has a fractional part.

For the latter step, one way would be to use the modf function , which returns both the fractional part (directly) and the integral part (by reference). If the fractional part is greater than zero (or some appropriately small fraction below which you're willing to tolerate), then the number has a fractional part.

The reason why this is better is because not everybody writes decimal fractions in the “12345.6789” format. Some countries use a comma instead, and I'm sure that's not the only variation. Let the number formatter handle such cases for you.

Answer 5

I wrote a little method to make things a little more natural if you use this sort of thing a whole bunch in your project:

+(BOOL)seeIfString:(NSString*)thisString ContainsThis:(NSString*)containsThis
{
    NSRange textRange = [[thisString lowercaseString] rangeOfString:[containsThis lowercaseString]];

    if(textRange.location != NSNotFound)
        return YES;

    return NO;
}

Enjoy!