Join Scott Gardner for an in-depth discussion in this video Define class-only protocols, part of Swift 3 Essential Training: Beyond the Basics.
- [Instructor] I'll keep going in the same exercise file…from the previous video.…Sometimes you may want to define a protocol that…can only be implemented by class types,…which are passed by reference, versus structures…and enumerations that are value types and passed by copy.…To require the type to be a class, write the class keyword…in the protocol's inheritance list.…And it must be listed first before any inherited protocols.…I'll define a ratable protocol…that must be implemented by a class.…As the author of this protocol, I want to make sure…that instances of a type that adopt ratable…do not get copied around by default, in which case…adding a rating might update a copy and not the original.…
So, I require the type to be a class.…Ratable will require a ratings property and two methods,…add rating and average rating.…Now I'll adopt ratable in book, and conform to it.…First by adding the ratings array, which I'll set…to an empty array by default,…and next I'll define the add rating method,…and first prevent ratings higher than five,…
- Adding source files, resources, links, and literals
- Adding pages to a playground
- Using overflow operators and bitwise operators
- Using ranges with strings
- Creating complex sequences
- Chaining higher-order functions
- Defining lazy properties
- Using failable initializers
- Mutating methods
- Working with singletons
- Nesting function types
- Creating error types and recursive enumerations
- Extending concrete types
- Referencing selectors and key paths
- Working with protocol-oriented programming
- Defining class-only protocols and optional protocols
- Using option sets, type checking, and casting operators
Skill Level Intermediate
Core Data for iOS and macOS Enterprise Developerswith Jon Bott1h 46m Intermediate
Distributing Your iOS App for Testing with TestFlightwith Ron Buencamino35m 10s Intermediate
iOS App Development: Test-Driven Developmentwith Harrison Ferrone2h 14m Intermediate
3. Strings and Characters
4. Sequences and Collections
5. Control Flow
6. Value and Reference Types
9. Access Control
Understand access control3m 47s
Next steps1m 2s
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