The Type System

Lessons

1. 01 Optionals Measuring how absence is expressed in the type, why a transforming closure never runs on nil, and where absence stops in nested layers. 13 min read
2. 02 Unwrapping Optionals Measuring when the right-hand side of if let and guard let, a ?? chain and optional chaining are evaluated. 14 min read
3. 03 Structures and Classes Measuring copying on assignment for structures, sharing for classes, when a default value is built, and why a copy appears at the first mutation. 13 min read
4. 04 Enumerations Measuring when a raw value and an associated value are set up, how pattern matching opens them, and why a computed property runs on every read. 13 min read
5. 05 Properties Measuring when stored, computed and observed properties, lazy properties and static let values are set up. 12 min read
6. 06 Protocols Measures when a value that fulfills a protocol requirement is evaluated: a default implementation runs on every call, but the conforming type decides the moment. 13 min read
7. 07 Extensions Measures adding methods, computed properties and protocol conformance to an existing type from the outside; shows that a stored property cannot be added, and the type-level exception. 13 min read
8. 08 Generics Applies one body to many types with type parameters and constraints; measures the transformer of a lazy sequence on every access and that of an eager map immediately. 13 min read
9. 09 Error Handling Measures that nothing after the `throw` line in the body of a throwing function ever runs, while a `defer` block runs on every exit. 14 min read
10. 10 Access Control Measures that making a cache `private` does not change the moment of evaluation, and that access control is decided at compile time. 14 min read