CODEWITHSUNDEEP
iphonexcodensstringnscfstring
Sindhia
Sindhia

Reputation: 411

NSString or NSCFString in xcode?

I m taking a NSMutabledictionary object in NSString like this :

NSString *state=[d valueForKey:@"State"];

Now sometimes state may be null and sometimes filled with text.So Im comparing it.While comparing state becomes NSString sometimes and NSCFString othertimes..So unable to get the desired result..

if([state isEqualToString@""])
{
//do something 
}
else
{
//do something
}

So while comparing it is returning nil sometimes.So immediately jumping into the else block.

I need a standard way to compare if the state is empty whether it is a NSString or NSCFString ...

How can I do it?

Upvotes: 2

Views: 3694

Answers (3)

Rajneesh071
Rajneesh071

Reputation: 31091

You can do this 

if([state isEqualToString:@""])
{
//do something 
}
else
{
//do something
}

Upvotes: 1

junaidsidhu
junaidsidhu

Reputation: 3580

You must have to type cast it to get the correct answer.

 NSString *state = (NSString *) [d valueForKey:@"State"];

  if(state != nil)
  {
      if(state.length > 0)
      {
           //string contains characters
      }
  }

Upvotes: -1

zneak
zneak

Reputation: 138261

If you're unable to get the result you want, I can assure you it's not because you get a NSCFString instead of a NSString.

In Objective-C, the framework is filled with cluster classes; that is, you see a class in the documentation, and in fact, it's just an interface. The framework has instead its own implementations of these classes. For instance, as you noted, the NSString class is often represented by the NSCFString class instead; and there are a few others, like NSConstantString and NSPathStore2, that are in fact subclasses of NSString, and that will behave just like you expect.

Your issue, from what I see...

Now sometimes state may be null and sometimes filled with text.

... is that in Objective-C, it's legal to call a method on nil. (Nil is the Objective-C concept of null in other languages like C# and Java.) However, when you do, the return value is always zeroed; so if you string is nil, any equality comparison to it made with a method will return NO, even if you compare against nil. And even then, please note that an empty string is not the same thing as nil, since nil can be seen as the absence of anything. An empty string doesn't have characters, but hey, at least it's there. nil means there's nothing.

So instead of using a method to compare state to an empty string, you probably need to check that state is not nil, using simple pointer equality.

if(state == nil)
{
    //do something 
}
else
{
    //do something
}

Upvotes: 2

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