检查是否包含空

Question

When I print the following I get (null)

NSLog(@"%@", [[responseObject objectAtIndex:i] objectForKey:@"child"]);

Now I want to do a validation to check if it returns (null) . How am I supposed to do this?

I tried the following but it doesn't work:

1.

 if (![[[responseObject objectAtIndex:i] objectForKey:@"child"] isEqualToString:@"(null)"]) {

}

2.

if (![[[responseObject objectAtIndex:i] objectForKey:@"child"]  isEqual:@"(null)"]) {
}

Answer 1

"null" isn't just a NSString . You should do some research into the concept of a null object.

What you're looking for can be written like this:

if (![[responseObject objectAtIndex:i] objectForKey:@"child"]) {
    //key "child" not in dictionary
}

Answer 2

(null) is the representation of nil displayed by NSLog .

You can write the following:

if ([[responseObject objectAtIndex:i] objectForKey:@"child"] == nil) {

}

Or a shorter alternative:

if (![[responseObject objectAtIndex:i] objectForKey:@"child"]) {

}

Answer 3

Another way to check is to use string length. I know other answers are just as good, I am just giving OP and anyone else in future some more options.

NSString *childStr = [[responseObject objectAtIndex:i]objectForKey:@"child"];

if ([childStr length] < 1)
{
  //no value specified - childStr is NULL
}
else
{ 
 //there is something in the childStr - throw a party!
}

Answer 4

NSUserDefaults *defaults=[NSUserDefaults standardUserDefaults];
if ([defaults objectForKey:@"hello"]) {
  NSLog(@"only if not null show %@",[defaults objectForKey:@"hello"]);
}

This is a way to check it from User Defaults. It will only print if the saved object does not equal null .