facebook/facebook-ios-sdk — comment on commit 60367ef741ae5063570f793520d9c7559a55fbcc
File:  line 0
By HamiltonSnow:

also ,in here FBRequest.h.h

that's why
-54 @property(nonatomic,assign) NSURLConnection* connection;
-55 @property(nonatomic,assign) NSMutableData* responseText;

use assign , use retain or strong is better?