CODEWITHSUNDEEP
objective-cnull
user1904273
user1904273

Reputation: 4764

Detect if NSNumber is zero, nil or 0

I have a variable in core data. I want to detect for the cases where it is nil zero, null or otherwise does not have a nice value such as 222 or 333.

This should be trivial but I am getting caught up in Objective-C's syntax.

Following code is not working:

if (_item.id!=nil && _item.id!=0) {
//do something
}

Of note id should be an NSNumber.

It is defined as

@property (nonatomic, retain) NSNumber * id;

I should clarify that it is not working when the value logs to console as 0.

Given the way variable types and core data work, I cannot tell you what causes the variable to log to console as '0' but something is causing it to do so. Basically, I want to exclude cases where the value is anything other than a non-zero integer (in mathematical, not computer science terms).

Upvotes: 2

Views: 7136

Answers (3)

Mohamed Ali
Mohamed Ali

Reputation: 59

To check the numeric value stored in an NSNumber, you have to call one of the methods which give you a primitive type.

e.g. integerValue, unsignedLongLongValue, doubleValue

To correctly check for nil and a value of 0, you need the following:

if (_item.id != nil && [_item.id intValue] != 0) {
    // code here
}

Because sending a message to a nil reference returns 0, you can take a shortcut:

if ([_item.id intValue] != 0)

Upvotes: 0

Jim Tierney
Jim Tierney

Reputation: 4105

As this NSManagedObject is of type NSNumber, simply check the intValue.

  if (!_item.id.intValue){
       //Method will stop in here if the id is nil/0 etc.
  }

However, it is not recommended to name a variable id, I suggest you rename it to itemId

In the same way you shouldn't name something 'string', or 'new' etc as these conflict with Apple's own native naming policies

Upvotes: 2

Avi
Avi

Reputation: 7552

To check the numeric value stored in an NSNumber, you have to call one of the methods which give you a primitive type.

e.g. integerValue, unsignedLongLongValue, doubleValue

To correctly check for nil and a value of 0, you need the following:

if (_item.id != nil && [_item.id intValue] != 0) {
    // code here
}

Because sending a message to a nil reference returns 0, you can take a shortcut:

if ([_item.id intValue] != 0) ...

This works because _item.id has to be non-nil to return a non-zero value from intValue.

Upvotes: 8

Related Questions