String in Objective-C

In Objective-C, you can use the NSNumberFormatter class to check if a string is a number. Here is an example of how to check if a string is a decimal number:

``objective-c
NSString *inputString = @"123.45";
NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
formatter.numberStyle = NSNumberFormatterDecimalStyle;
NSNumber *number = [formatter numberFromString:inputString];
if (number != nil) {
NSLog(@"%@ is a number", inputString);
} else {
NSLog(@"%@ is not a number", inputString);
}


In this example, we create a NSNumberFormatter object and set its numberStyle property to NSNumberFormatterDecimalStyle, which allows it to recognize decimal numbers. We then use the numberFromString: method to attempt to convert the input string to a number. If the resulting NSNumber object is not nil, then the input string is a number.

Here's another example for checking if a string is an integer:

In this example, we use the same NSNumberFormatter object and the numberFromString: method to attempt to convert the input string to a number. We also check if the number is an integer by comparing its intValue and doubleValue`. If they are equal, then the input string is an integer.