Method To Delete 2nd Label, Then First Label, Not Functioning Correctly

Question

I know I am missing something obvious, but I just cannot see it. This method is meant to compare the text of a label to the text of a text box, and then delete the text. So if t

Answer 1

Compairing String literals using == is not guaranteed to behave as you might expect. Use isEqual: or isEqualToString: instead.

See http://nshipster.com/equality/.

Answer 2

When you are comparing NSStrings with == what you are actually comparing are two memory addresses and that is not what you are really intended for. You want to compare the values of two strings what == operator is not suitable for and thus you are getting the warning

Direct comparison of a string literal has undefined behavior.

To compare the values of NSStrings you should use isEqualToString: method. You could have also use isEqual: method derived from NSObject class but that is not suitable for Unicode comparison. So isEqualToString: is always the safest bet.

After using isEqualToString: your code should look something like:

-(IBAction)btnDelete:(id)sender
{
  if ([self.lblFabric2.text isEqualToString:self.txtType.text])
   {
     self.lblFabric2.text = @"";
   }
  else
   {
     self.lblFabric1.text=@"";
   }
}

Answer 3

You should not use == or != for string comparison in Objective C. You need to use the isEqualToString or isEqual method.

if (([self.lblFabric2.text isEqualToString:self.txtType.text]))

When you use == or != you are comparing the pointers where the strings are stored.

Answer 4

To compare NSStrings use:

if ([myString1 isEqualToString:myString2])

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