How can i check string contains unknown character? - ios

Question

I am calling webservice in the response i am getting the string.
When i print the string in NSLog it return empty string and When i check the length it returns 1.
So my problem is that how can i check the string is empty or not.
#define CHECK_NA_STRING(str) (str == (id)[NSNull null] || [str length] == 0)?#"N/A":str
NSLog(#"%#",CHECK_NA_STRING([dict objectForKey:#"ADDRESS_A"])); // nothing empty string
NSLog(#"%d",[CHECK_NA_STRING([dict objectForKey:#"ADDRESS_A"]) length]); // return 1
So how can i check that string is empty or not?
Thanks.

Answer 1

So the string is just a space? Then it will still have a length of 1.
Try:
NSString* string = ...;
if([string isKindOfClass:[NSString class]])
{
NSCharacterSet* invertedWhitespaceSet = [[NSCharacterSet whitespaceAndNewlineCharacterSet] invertedSet];
const NSRange nonEmptyCharacterRange = [string rangeOfCharacterFromSet:invertedWhitespaceSet options:NSCaseInsensitiveSearch];
if(nonEmptyCharacterRange.location == NSNotFound)
{
// Empty invalid string
}
else
{
// Non-empty valid string
}
}

Answer 2

The string is not considered empty if it contains a binary zero (null character). For instance, try this code:
#define CHECK_NA_STRING(str) (str == (id)[NSNull null] || [str length] == 0)?#"N/A":str
NSMutableDictionary *dict = [[NSMutableDictionary alloc] init];
[dict setObject:#"\0" forKey:#"ADDRESS_A"];
NSLog(#"%#",CHECK_NA_STRING([dict objectForKey:#"ADDRESS_A"])); // nothing empty string
NSLog(#"%d",[CHECK_NA_STRING([dict objectForKey:#"ADDRESS_A"]) length]); // return 1
Nothing will print for the first NSLOG, but the second will print a "1". Indeed the string is one character long; it just messes up your NSLOG.
You probably want to test for some valid range of responses, or some invalid range. Perhaps, you could use a regular expression.