Is Checking The Pointer Of An Object With Negation Operator The Same As With Comparing It To Nil?

Question

I maybe naming it wrong, so please correct me.

I just want to know if this

if(!obj)
{
    //do something
}

is exactly the same as this

if(obj == nil)
{

}

I mean are they both checking whether the object points to nil?

I'll just add this link http://stackoverflow.com/questions/11821282/objectivec-if-obj-and-if-obj-nil-which-is-better where the top answerer seems to have done some research on the compilation code — Larme, Nov 09 '16 at 12:16

Sergey Kalinichenko · Accepted Answer · 2016-11-09T12:12:18.630

2

Yes, this is exactly the same. ! operator turns anything other than nil into zero, while nil becomes 1. Therefore, you get exactly the same results as the comparison with nil.

Similarly, using if (obj) is logically identical to if (obj != nil). This convention is inherited from C, where pointers are commonly used in conditions, and NULL-checked with ! operator.

edited Nov 09 '16 at 12:12

answered Nov 09 '16 at 12:10

Sergey Kalinichenko

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score 1 · Answer 2 · answered Nov 09 '16 at 12:09

1

Yes, it's the same. That's right. Yep.

answered Nov 09 '16 at 12:09

joerick

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Sorry, my answer had to be at least 30 characters long! >_ – joerick Nov 09 '16 at 12:10

Is Checking The Pointer Of An Object With Negation Operator The Same As With Comparing It To Nil?

2 Answers2