Airbnb

iOS

1. Implement a UIImage Category that supports LRU Image Cache with cache size of 10 images
2. Download the image without blocking the main thread
3. Dispatch to another queue for async image fetching

4. Need to consider thread safety and dispatch barrier

5. Imagine UITableView and UICollectionView haven't been invented yet, implement a Horizontal Table View that recycles memories.

6. Create your own dataSource protocals: numberOfColumns and cellForColumnsAtIndexPath
7. Initialization
8. Get call back when user scroll your view: 为recycle memory做准备。因为我们subclass的已经是一个UIScrollView了，所以可以直接delegate给自己，然后得到scrollViewDidScroll的call back

9. Recycle memory: 当有cells被滑动到屏幕外边了之后(通过上一步来判断)，把这些cells装到一个queue上，然后新的cells来重复使用这个queue里的memory, 原理和UITableView一模一样。不过当时面试官说不用queue这么复杂了，这里用一个set就行。

10. Implement a view controller with the following functions

11. Display an image
12. A delete button

13. Drag the image to the button and delete the image

14. How to create a collectionView within the cells of a tableView programmatically

15. Review the core values

16. Be a host
17. Champion the mission
18. Every frame matters
19. Be a cereal entreprenual

1. Text Justification