How do I test if a string is empty in Objective C?

Question

How do I test if an NSString is empty in Objective C?

Answer 1

The best way is to use the category.
You can check the following function. Which has all the conditions to check.

-(BOOL)isNullString:(NSString *)aStr{
        if([(NSNull *)aStr isKindOfClass:[NSNull class]]){
            return YES;
        }
        if ((NSNull *)aStr  == [NSNull null]) {
            return YES;
        }
        if ([aStr isKindOfClass:[NSNull class]]){
            return YES;
        }
        if(![[aStr stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] length]){
            return YES;
        }
        return NO;
    }

Answer 2

- (BOOL)isEmpty:(NSString *)string{
    if ((NSNull *) string == [NSNull null]) {
        return YES;
    }
    if (string == nil) {
        return YES;
    }
    if ([string length] == 0) {
        return YES;
    }
    if ([[string stringByTrimmingCharactersInSet: [NSCharacterSet whitespaceAndNewlineCharacterSet]] length] == 0) {
        return YES;
    }
    if([[string stringByStrippingWhitespace] isEqualToString:@""]){
        return YES;
    }
    return NO;
}

Answer 3

check this :

if ([yourString isEqualToString:@""])
{
    NsLog(@"Blank String");
}

Or

if ([yourString length] == 0)
{
    NsLog(@"Blank String");
}

Hope this will help.

Answer 4

May be this answer is the duplicate of already given answers, but i did few modification and changes in the order of checking the conditions. Please refer the below code:

+(BOOL)isStringEmpty:(NSString *)str
    {
        if(str == nil || [str isKindOfClass:[NSNull class]] || str.length==0) {
            return YES;
       }
        return NO;
    }

Answer 5

You have 2 methods to check whether the string is empty or not:

Let's suppose your string name is NSString *strIsEmpty.

Method 1:

if(strIsEmpty.length==0)
{
    //String is empty
}

else
{
    //String is not empty
}

Method 2:

if([strIsEmpty isEqualToString:@""])
{
    //String is empty
}

else
{
    //String is not empty
}

Choose any of the above method and get to know whether string is empty or not.

Answer 6

Just pass your string to following method:

+(BOOL)isEmpty:(NSString *)str
{
    if(str.length==0 || [str isKindOfClass:[NSNull class]] || [str isEqualToString:@""]||[str  isEqualToString:NULL]||[str isEqualToString:@"(null)"]||str==nil || [str isEqualToString:@"<null>"]){
        return YES;
    }
    return NO;
}