伊谢尔伦2017-04-21 10:59:12
According to NetEase’s mobile device report this year, there are still 2% of devices below iOS 4.
According to Apple's idea of elimination from generation to generation, the point when ARC is no longer under NDA is also the point in time when iOS 3 is declared dead.
Whether those two percentage points of users will use your software and whether you care about those two percentage points of users are the main factors in the decision. You also have to consider the expected completion time of the project. For example, after three months, the percentage of devices below iOS 4 will be even smaller.
The main devices using iOS3 are iPhone 2G, iPhone 3G and the first generation touch
大家讲道理2017-04-21 10:59:12
arc is not a runtime function, so it does not depend on the runtime environment.
Arc can be understood as a compile-time code optimization. Its working principle is that during the compilation process, your source code is automatically added with retain release autorelease and so on.
So, you can use arc at any time