Objective-C how to check if a string is null

Question

SO I wish to check to see if the item in my array [clientDataArray objectForKey:@"ClientCompany"] is nil.

    temp = [clientDataArray objectForKey:@"ClientCompany"];
    if (temp != [NSNull null]) infofieldCompany.text = temp;

So far I have been able to achieve this through the above code, but it does give me the warnings

• warning: NSArray may not respond to -objectForKey:
• warning: comparison of distinct Objective-C types struct NSNull * and struct NSString * lacks a cast

My main interest is the second warning, but the first warning also interest me. How should I adapt my above code?

Answer 1

After trying all the options, i think this is the best option to comapre NSString null

if ( temp != ( NSString *) [ NSNull null ] )
{
  // do some thing
}

Answer 2

Your first warning looks like you're trying to call objectForKey on an NSArray. Which isn't going to work, as NSArray doesn't have an objectForKey method.

As for the second warning you can just compare directly with nil, ie:

if (temp != nil)

or since nil is equivalent to 0, you can also just do:

if (temp)