Guidelines

swift.org/documentation/api-design-guidelines

Clarity the point of use

• No Prefixes in Swift-only Frameworks

Values and References

Classes - Reference Types Structs and Enums - Value Types

Choosing - Reference or Value ?

Prefer structs over classes

• Only choose classes when reference semantics are important

Classes can make a good choice when

• You need a reference counting and deinitialization
• The value is held centrally and shared
• Where there is held centrally and shared

Value and Reference Semantics

Value types makes copy of reference types

Protocols and Generics

Don’t literally start with a protocol

• Start with concrete use cases
• Discover a need for generic code
• Try to compose solutions from existing protocols first
• Consider a generic type instead of a protocol

Protocol for code reuse, otherwise use generics.

Key Path Member Lookup

Swift Evolution: SE-0252 @dynamicMemberLookup & subscript $ backing storage property, binding property, key path member lookup

Property Wrapper

@LateInitialized <- give a private policy Provides similar benefits to the built-in lazy

• Eliminates boilerplate
• Documents semantics at the point of definition

Property wrappers reuse computed property definitions.

Using Property Wrappers

Uses of property wrappers expand into a stored property and a computed property

Using the DefensiveCopying Property Wrapper

@DefensiveCopying Variables can be initialized in their declaration

• Property Wrappers in UserDefault
• Property Wrappers in SwiftUI