Minor updates to AFURLConnectionOperation documentation

AFNetworking/AFURLConnectionOperation.h

@@ -22,8 +22,10 @@
 
 #import <Foundation/Foundation.h>
 
+#import <Availability.h>
+
 /**
- `AFURLConnectionOperation` is an `NSOperation` that implements NSURLConnection delegate methods.
+ `AFURLConnectionOperation` is a subclass of `NSOperation` that implements `NSURLConnection` delegate methods.
  
  ## Subclassing Notes
  
@@ -48,11 +50,11 @@
   
  ## Class Constructors
  
- Class constructors, or methods that return an unowned (zero retain count) instance, are the preferred way for subclasses to encapsulate any particular logic for handling the setup or parsing of response data. For instance, `AFJSONRequestOperation` provides `JSONRequestOperationWithRequest:success:failure:`, which takes block arguments, whose parameter on for a successful request is the JSON object initialized from the `response data`.
+ Class constructors, or methods that return an unowned instance, are the preferred way for subclasses to encapsulate any particular logic for handling the setup or parsing of response data. For instance, `AFJSONRequestOperation` provides `JSONRequestOperationWithRequest:success:failure:`, which takes block arguments, whose parameter on for a successful request is the JSON object initialized from the `response data`.
  
  ## Callbacks and Completion Blocks
  
- The built-in `completionBlock` provided by `NSOperation` allows for custom behavior to be executed after the request finishes. It is a common pattern for class constructors in subclasses to take callback block parameters, and execute them conditionally in the body of its `completionBlock`. Make sure to handle cancelled operations appropriately when setting a `completionBlock` (e.g. returning early before parsing response data). See the implementation of any of the `AFHTTPRequestOperation` subclasses for an example of this.
+ The built-in `completionBlock` provided by `NSOperation` allows for custom behavior to be executed after the request finishes. It is a common pattern for class constructors in subclasses to take callback block parameters, and execute them conditionally in the body of its `completionBlock`. Make sure to handle cancelled operations appropriately when setting a `completionBlock` (i.e. returning early before parsing response data). See the implementation of any of the `AFHTTPRequestOperation` subclasses for an example of this.
  
  Subclasses are strongly discouraged from overriding `setCompletionBlock:`, as `AFURLConnectionOperation`'s implementation includes a workaround to mitigate retain cycles, and what Apple rather ominously refers to as ["The Deallocation Problem"](http://developer.apple.com/library/ios/#technotes/tn2109/).
  
@@ -69,7 +71,7 @@
  
  - `-copy` and `-copyWithZone:` return a new operation with the `NSURLRequest` of the original. So rather than an exact copy of the operation at that particular instant, the copying mechanism returns a completely new instance, which can be useful for retrying operations.
  - A copy of an operation will not include the `outputStream` of the original.
- - Operation copies do not include `completionBlock`. `completionBlock` often strongly captures a reference to `self`, which, perhaps surprisingly, would otherwise point to the _original_ operation when copied.
+ - Operation copies do not include `completionBlock`. `completionBlock` often strongly captures a reference to `self`, which would otherwise have the unintuitive side-effect of pointing to the _original_ operation when copied.
  */
 @interface AFURLConnectionOperation : NSOperation <NSURLConnectionDelegate, NSURLConnectionDataDelegate, NSCoding, NSCopying>