Ios – the way to quick-switch between tabs in Xcode 4

Stop, stop, stop.

This is not how Vim's tabs are designed to be used. In fact, they're misnamed. A better name would be "viewport" or "layout", because that's what a tab is—it's a different layout of windows of all of your existing buffers.

Trying to beat Vim into 1 tab == 1 buffer is an exercise in futility. Vim doesn't know or care and it will not respect it on all commands—in particular, anything that uses the quickfix buffer (:make, :grep, and :helpgrep are the ones that spring to mind) will happily ignore tabs and there's nothing you can do to stop that.

Instead:

• :set hidden
  If you don't have this set already, then do so. It makes vim work like every other multiple-file editor on the planet. You can have edited buffers that aren't visible in a window somewhere.
• Use :bn, :bp, :b #, :b name, and ctrl-6 to switch between buffers. I like ctrl-6 myself (alone it switches to the previously used buffer, or #ctrl-6 switches to buffer number #).
• Use :ls to list buffers, or a plugin like MiniBufExpl or BufExplorer.

The last two are identical; "atomic" is the default behavior (note that it is not actually a keyword; it is specified only by the absence of nonatomic -- atomic was added as a keyword in recent versions of llvm/clang).

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. (Note: @synthesize is now the default behavior in recent versions of LLVM. There is also no need to declare instance variables; they will be synthesized automatically, too, and will have an _ prepended to their name to prevent accidental direct access).

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.

Adding to this:

atomicity of a single property also cannot guarantee thread safety when multiple dependent properties are in play.

Consider:

 @property(atomic, copy) NSString *firstName;
 @property(atomic, copy) NSString *lastName;
 @property(readonly, atomic, copy) NSString *fullName;

In this case, thread A could be renaming the object by calling setFirstName: and then calling setLastName:. In the meantime, thread B may call fullName in between thread A's two calls and will receive the new first name coupled with the old last name.

To address this, you need a transactional model. I.e. some other kind of synchronization and/or exclusion that allows one to exclude access to fullName while the dependent properties are being updated.