What does retain as property attribute exactly do in objective-c?

Question

If I declare a public property as :

@property (retain) NSString * name;

Then how does the compiler implicitly implement this? I have read that the retain gains ownership over the instance variable "_name". I have also read that "retain" message increases the reference count of the object. So each time I call the setter for "name" property in the above example, will it increase the reference count?

So after this,

object.name=@"name1";
object.name=@"name2";

Will the reference count be 2?

Possible duplicate http://stackoverflow.com/questions/2255861/property-and-retain-assign-copy-nonatomic-in-objective-c — Sujay, Jun 04 '15 at 10:52

score 0 · Answer 1 · edited Mar 06 '18 at 10:46

0

According to Blamdarot in this answer:

"retain" is needed when the attribute is a pointer to an object. The setter generated by @synthesize will retain (aka add a retain count) the object. You will need to release the object when you are finished with it.

edited Mar 06 '18 at 10:46

Pang

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answered Jun 04 '15 at 10:55

Sujay

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score 0 · Answer 2 · answered Jun 08 '15 at 08:51

To answer your specific question:

object.name = @"name1";

name now holds a strong reference to the "name1" string instance.

object.name = @"name2";

name now holds a strong reference to the "name2" string instance. No object holds a reference to the "name1" instance, and a release statement will be inserted by the compiler for "name1". (in practice, the first statement will likely be optimized away entirely).

What does retain as property attribute exactly do in objective-c?

2 Answers2