Rules of iOS development

1. Keep a class small - 83.
2. TableViewCell reusing may cause a problem, when common cell is not set correctly.83
3. TableView use model instead of indexPath, stabler when needs change.84
4. Block property must use copy.84
5. When we debug and change code, the program is running with old code.
6. CollectionView only alloc two cells,we can use it to create a view scrolling inifinitly.