iOS compare string to null

tranvutuan · Feb 9, 2012

After parsing and get values for each elements from XML, one of the field is null like below

Code:

myXML.h
@property (strong, nonatomic) NSString *address;
@property (strong, nonatomic) NSString *phone;

Below is my xml structure

Code:

<myXML>
  <address> A Street </address>
  <phone>  (null)      </phone>
</myXML>

I am doing a checking :

Code:

if ( ![myMXL.phone isEqualToString:@"null"] ) {
      NSLog(@"phone is not null");
else
      NSLog(@"phone is null");

After running the codes, the debugger gives me

Code:

phone is not null

It seems isEqualToString is not working.I also try !(myXML.phone == NULL) and !([myXML.phone isEqual:NULL]), but still get same problem
Does anyone have an idea about this.. pls advice me. Thanks

tranvutuan · Feb 9, 2012

tranvutuan said:
After parsing and get values for each elements from XML, one of the field is null like below

Code:

myXML.h @property (strong, nonatomic) NSString *address; @property (strong, nonatomic) NSString *phone;

Below is my xml structure

Code:

<myXML> <address> A Street </address> <phone> (null) </phone> </myXML>

I am doing a checking :

Code:

if ( ![myMXL.phone isEqualToString:@"null"] ) { NSLog(@"phone is not null"); else NSLog(@"phone is null");

After running the codes, the debugger gives me

Code:

phone is not null

It seems isEqualToString is not working.I also try !(myXML.phone == NULL) and !([myXML.phone isEqual:NULL]), but still get same problem
Does anyone have an idea about this.. pls advice me. Thanks

I've just found the way how to solve this issue. Because phone is NNString so we can count the length of it. Therefore, instead of comparing to null, I did

Code:

if (!([phone length] == 0 ))
   // do sth here

But I am still looking for other solutions, so please answer if you have another solution. Thanks

dantastic · Feb 9, 2012

(null) is not a string, it's nothing. you can't compare it to the string "null"

if you want to check for null do

Code:

if (myMXL.phone) {
   NSLog(@"phone has a value: %@", myMXL.phone);
} else {
   NSLog(@"this will print (null): %@", myMXL.phone);
}

tranvutuan · Feb 9, 2012

dantastic said:
(null) is not a string, it's nothing. you can't compare it to the string "null"

if you want to check for null do

Code:

if (myMXL.phone) { NSLog(@"phone has a value: %@", myMXL.phone); } else { NSLog(@"this will print (null): %@", myMXL.phone); }

I have just gave it a try but it does not work... What I got from the console is

Code:

phone has a value :(null)

I dont know why because we already know from OP, my phone is null

dantastic · Feb 9, 2012

odd..
Or do you actually have a string with "(null)" in it?
If you add

Code:

if (myMXL.phone) {
   NSLog(@"phone has a value: >%@< of Kind: %@, length: %i", myMXL.phone, [myMXL.phone class], [myMXL.phone length]);
} else {
   NSLog(@"this will print (null): %@", myMXL.phone);
}

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iOS compare string to null

tranvutuan

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tranvutuan

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tranvutuan

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