What is the correct attribute for a setter/getter for an int?

I have seen a number of different ways to propertise/synthesize a int, but I don't know the proper way.

I usually do:

@property (nonatomic, assign) int myInt

But I have seen people use:

@property (non开发者_如何学运维atomic) int myInt
@property int myInt

Which way is correct?

Here is a great post about the difference between atomic and nonatomic:

Assuming that you are @synthesizing the method implementations, atomic vs. non-atomic changes the generated code. If you are writing your own setter/getters, atomic/nonatomic/retain/assign/copy are merely advisory.

With atomic, the synthesized setter/getter will ensure that a whole value is always returned from the getter or set by the setter, regardless of setter activity on any other thread. That is, if thread A is in the middle of the getter while thread B calls the setter, an actual viable value -- an autoreleased object, most likely -- will be returned to the caller in A.

In nonatomic, no such guarantees are made. Thus, nonatomic is considerably faster than atomic.

What atomic does not do is make any guarantees about thread safety. If thread A is calling the getter simultaneously with thread B and C calling the setter with different values, thread A may get any one of the three values returned -- the one prior to any setters being called or either of the values passed into the setters in B and C. Likewise, the object may end up with the value from B or C, no way to tell.

Ensuring data integrity -- one of the primary challenges of multi-threaded programming -- is achieved by other means.

Note that the default is atomic, so the last example is equivalent to

@property (atomic) int myInt

Another default value is assign, therefore these two options are equivalent:

@property (nonatomic, assign) int myInt
@property (nonatomic) int myInt

And, similarly, the following are also equivalent

@property (atomic, assign) int myInt
@property (atomic) int myInt

EDIT: As Josh points out, atomic being included is a hypothetical example.

defaults are assign and atomic

It's more of a style issue than an issue of technical correctness. For an int type, the only thing that has to true the assign modifier (because you don't retain scalars). Otherwise, it's context specific: readwrite or readonly, atomic or nonatomic, it depends on the application.

Note that if you don't specify a modifier, the default applies (atomic, readwrite, assign). So your example your first other example are identical, and the third only differs in atomicity.

@property(nonatomic,assign)int myVariable;

always remember assign will be used for primitive data types like int , bool