This document provides an overview of migrating code from Objective-C to Swift. It discusses keeping APIs compatible by using toll-free bridging for data types and protocols. It also provides a checklist for migration, including importing dependencies and adding nullability. Lastly, it recommends a method-by-method approach using extensions for medium to large projects and migrating to Swift idioms last.

1. Objective-C
to
Swift

2. story from 20k+ line of codes

3. Topics
• read “Migrating Your Objective-C Code to Swift”
• API Compatible
• Migration Check List
• Migration for small Project
• Migration for medium-large Project

4. API Compatible
Toll free bridge
• NSString <-> String
• NSArray <-> [AnyObject]
• NSObject <-> [NSObject : AnyObject]

5. API Compatible
Delegate
@protocol UITableViewDataSource<NSObject>
@required
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section;
@optional
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView;
….
@objc protocol UITableViewDataSource {
public func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int
optional public func numberOfSectionsInTableView(tableView: UITableView) -> Int
….

6. API Incompatible
• Some NSString APIs.
Exp: stringByAppendingPathComponent
Solution: (str as NSString).stringByAppendingPathComponent("hello")

7. Migration Check List
• Migrate class by class, start from sub-class
• Import all dependencies to Bridging-Header.h
• Import Project-Swift.h to .m
• Use @class for .h
• Storyboard: re-type your class name

8. Master Detail Sample

9. Master Detail Sample

10. Migration for medium-large Project
• Add Nullability to your Objective-C
• Unit Test
• Method by method using Extension

11. Last step
• Migrate to swift way ( get, set, willSet, didSet, map,
flatMap, filter, extension, lazy, struct, …)

12. More
• https://medium.com/swifty-coffee