How to validate the empty string in Objective C?

I want to validate the string value after getting in the below parser delegate method

I have tried like [string lengt开发者_如何学Pythonh]>0 ,(string !=NULL) in if condition still blank string is printed in the NSlog.So what is the efficient method to validate the sting.I have used the below code.

- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string {   
    if ([elemName isEqualToString:@"productName"]) {
        if (!prodStringValue) {
            prodStringValue = [[NSMutableString alloc] initWithCapacity:50];
        }
        [prodStringValue appendString:string];
        if(prodStringValue && [prodStringValue length]>0 && (prodStringValue !=NULL))
        {
            prodNameStr = prodStringValue;
        NSLog(@"productName:%@",prodNameStr);
        }
        if(string && [string length]>0 && (string !=NULL))
        {
            prodNameStr = string;
            NSLog(@"productName:%@",string);
        }

    }
}

Do you have whitespaces in this "empty" string? Be sure to delete them using

NSString *trimmedString = [string stringByTrimmingCharactersInSet:
                              [NSCharacterSet whitespaceAndNewlineCharacterSet]];

You can check if [string length] == 0. This will check if it's a valid but empty string (@"") as well as if its nil, since calling length on nil will also return 0.

You may use the following code instead of all three checks, I suppose.

[prodStringValue isEqualToString:@""];

And, BTW

if (prodStringValue)

equals to

if (prodStringValue != nil) // nil = NULL in objc

if (str == Nil)

Try This. Works For Me.

you can try this below few lines of code

NSString *trimedstr  = [string stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];


if(trimedstr != [NSNull null]&& ![trimedstr isEqualToString:@""])
{
    if([trimedstr length]>0)
    {
        NSLog(@"%@", trimedstr);
    }
}

In case of string is NULL and you check it's length then it will crash. so you may try.

string  = [string stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];


if(string != [NSNull null])
{
    if([string length]>0)
    {
        NSLog(@"%@",string);
    }
}

        [str isEqualToString:@""]

It is best way for nil string.