Generics in Theory and Practice

@MicheleTitolo

What We’ll Cover

What Is Generic Programming

Super Reusable

Type Independent

The Generics Manifesto

Not A Promise

Parts Implemented In Swift 3

Generics In The Standard Library

Collections

Can Hold Anything

Force Type Decisions

Global Functions

Widely Applicable

Transformations

Single Type Constraint If Any

Language Limitations

Variables That Are Classes + Protocols

Protocols With Associated Types

The stdlib Is Protocol Oriented

public init<Subject, C : Collection where C.Iterator.Element == Child, C.SubSequence : Collection, C.SubSequence.Iterator.Element == Child, C.SubSequence.Index == C.Index, C.SubSequence.Indices : Collection, C.SubSequence.Indices.Iterator.Element == C.Index, C.SubSequence.Indices.Index == C.Index, C.SubSequence.Indices.SubSequence == C.SubSequence.Indices, C.SubSequence.SubSequence == C.SubSequence, C.Indices : Collection, C.Indices.Iterator.Element == C.Index, C.Indices.Index == C.Index, C.Indices.SubSequence == C.Indices>(_ subject: Subject, children: C, displayStyle: Mirror.DisplayStyle? = default, ancestorRepresentation: Mirror.AncestorRepresentation = default)

One-Offs

Except When Working Around Language Limitations

Being Cool

What Can We Learn?

Generics Have Purpose

Design Decision Or Last Resort

Create True Reusability

Does Type Matter?

If It Matters, Probably Not Generic

Surface And Enforce Type Decisions

Using Generics Are Making Type Decisions

Generics Enforce That Choice

Any Is Poor Form

Coming Soon

Recursive Protocol Constraints

Associatedtypes Reference Enclosing Type

Sequence

And Leaky Abstractions

Nested Generics

Compiler Feature

Generics Can Contain Generics

Enhanced Existentials

Generic Types Are Enforced At Compile Time

Existential Types Are Enforced At Runtime

id<UITableViewDataSource, UITableViewDelegate>

UITableViewDataSource & UITableViewDelegate

Only Works With Concrete Protocols In Swift 3

Workaround With Generics

Goal To Be Fixed In Swift 4

Swift Is Evolving!

Get Involved

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