Swift in Depth
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An excellent guide to using the advanced features of Swift to produce clean, high-performing code. The content is masterfully delivered, making it easy to quickly level-up your skills.
Swift is more than just a fun language to build iOS applications with. It features a host of powerful tools that, if effectively used, can help you create even better apps with clean, crystal-clear code and awesome features. Swift in Depth is designed to help you unlock these tools and quirks and get developing next-gen apps, web services, and more!
Table of Contents takes you straight to the bookdetailed table of contents
1 Introducing Swift in depth
1.1 The sweet spot of Swift
1.2 Below the surface
1.3 Swift’s downsides
1.3.1 ABI Stability
1.3.2 Strictness
1.3.3 Protocols are tricky
1.3.4 Concurrency
1.3.5 Venturing away from Apple’s platforms
1.3.6 Compile times
1.4 What you will learn in this book
1.5 How to make the most of this book
1.6 Minimum qualifications
1.7 Swift version
Summary
2 Modeling data with enums
2.1 Or vs. and
2.1.1 Modeling data with a struct
2.1.2 Turning a struct into an enum
2.1.3 Deciding between structs and enums
2.2 Enums for polymorphism
2.2.1 Compile-time polymorphism
2.3 Enums instead of subclassing
2.3.1 Forming a model for a workout app
2.3.2 Creating a superclass
2.3.3 The downsides of subclassing
2.3.4 Refactoring a data model with enums
2.3.5 Deciding on subclassing or enums
2.3.6 Exercises
2.4 Algebraic data types
2.4.1 Sum types
2.4.2 Product types
2.4.3 Distributing a sum over an enum
2.4.4 Exercise
2.5 A safer use of strings
2.5.1 Dangers of raw values
2.5.2 Matching on Strings
2.5.3 Exercises
2.6 Closing thoughts
Summary
Answers
3 Writing cleaner properties
3.1 Computed properties
3.1.1 Modelling an exercise
3.1.2 Converting functions to computed properties
3.1.3 Rounding up
3.2 Lazy properties
3.2.1 Creating a learning plan
3.2.2 When computed properties don’t cut it
3.2.3 Using lazy properties
3.2.4 Making a lazy property robust
3.2.5 Mutable properties and lazy properties
3.2.6 Exercises
3.3 Property observers
3.3.1 Trimming whitespace
3.3.2 Trigger property observers from initializers
3.3.3 Exercises
3.4 Closing thoughts
Summary
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4 Making optionals second nature
4.1 The purpose of optionals
4.2 Clean optional unwrapping
4.2.1 Matching on optionals
4.2.2 Unwrapping techniques
4.2.3 When you’re not interested in a value
4.3 Variable shadowing
4.3.1 Implementing CustomStringConvertible
4.4 When optionals are prohibited
4.4.1 Adding a computed property
4.5 Returning optional strings
4.6 Granular control over optionals
4.6.1 Exercises
4.7 Falling back when an optional is nil
4.8 Simplifying optional enums
4.8.1 Exercise
4.9 Chaining optionals
4.10 Constraining optional booleans
4.10.1 Reducing a boolean to two states
4.10.2 Falling back on true
4.10.3 A boolean with three states
4.10.4 Implementing RawRepresentable
4.10.5 Exercise
4.11 Force unwrapping guidelines
4.11.1 When force unwrapping is "acceptable"
4.11.2 Crashing with style
4.12 Taming Implicitly Unwrapped Optionals
4.12.1 Recognizing IUO’s
4.12.2 IUO’s in practice
4.12.3 Exercise
4.13 Closing thoughts
Summary
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5 Demystifying initializers
5.1 Struct initializer rules
5.1.1 Custom initializers
5.1.2 Struct initializer quirk
5.1.2 Exercises
5.2 Initializers and subclassing
5.2.1 Creating a board game superclass
5.2.2 BoardGame’s initializers
5.2.3 Creating a subclass
5.2.4 Losing convenience initializers
5.2.5 Getting the superclass initializers back
5.2.6 Exercise
5.3 Minimizing class initializers
5.3.1 Convenience overrides
5.3.2 Subclassing a subclass
5.3.3 Exercise
5.4 Required initializers
5.4.1 Factory methods
5.4.2 Protocols
5.4.3 When classes are final
5.4.4 Exercises
5.5 Closing thoughts
Summary
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6 Effortless error handling
6.1 Errors in Swift
6.1.1 The Error protocol
6.1.2 Throwing errors
6.1.3 Swift doesn’t reveal errors
6.1.4 Keeping the environment in a predictable state
6.1.5 Exercises
6.2 Error propagation and catching
6.2.1 Propagating errors
6.2.2 Adding technical details for troubleshooting
6.2.3 Centralizing error handling
6.2.4 Exercises
6.3 Delivering pleasant APIs
6.3.1 Capturing validity within a type
6.3.2 Try?
6.3.3 Try!
6.3.4 Returning optionals
6.3.5 Exercises
6.4 Closing thoughts
Summary
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7 Generics
7.1 The benefits of generics
7.1.1 Creating a generic function
7.1.2 Reasoning about generics
7.1.3 Exercises
7.2 Constraining generics
7.2.1 Needing a constrained function
7.2.2 The Equatable and Comparable protocols
7.2.3 Constraining means specializing
7.2.4 Implementing Comparable
7.2.5 Constraining versus flexibility
7.3 Multiple constraints
7.3.1 The Hashable protocol
7.3.2 Combining constraints
7.3.3 Exercise
7.4 Creating a generic type
7.4.1 Wanting to combine two Hashable types
7.4.2 Creating a Pair type
7.4.3 Multiple generics
7.4.4 Conforming to Hashable
7.4.5 Exercise
7.5 Generics and subtypes
7.5.1 Subtyping and invariance
7.5.2 Invariance in Swift
7.5.3 Swift’s generic types get special privileges
7.6 Closing thoughts
Summary
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8 Putting the pro in Protocol-Oriented Programming
8.1 Runtime versus compile time
8.1.1 Creating a protocol
8.1.2 Generics versus protocols
8.1.3 A trade-off with generics
8.1.4 Moving to runtime
8.1.5 Choosing between compile-time and runtime
8.1.6 When a generic is the better choice
8.1.7 Exercises
8.2 The why of associated types
8.2.1 Running into a shortcoming with protocols
8.2.2 Trying to make everything a protocol
8.2.3 Designing a generic protocol
8.2.4 Modeling a protocol with associated types
8.2.5 Implementing a PAT
8.2.6 PATs in the standard library
8.2.7 Other uses for associated types
8.2.8 Exercises
8.3 Passing protocols with associated types
8.3.1 Where clauses with associated types
8.3.2 Types constraining associated types
8.3.3 Cleaning up our API with Protocol inheritance
8.3.4 Exercises
8.4 Closing thoughts
Summary
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9 Iterators, Sequences, and Collections
9.1 Iterating
9.1.1 IteratorProtocol
9.1.2 The IteratorProtocol
9.1.3 The Sequence protocol
9.1.4 Taking a closer look at Sequence
9.2 The powers of Sequence
9.2.1 filter
9.2.2 forEach
9.2.3 enumerated
9.2.4 Lazy iteration
9.2.5 Reduce
9.2.6 Reduce into
9.2.7 zip
9.2.8 Exercise
9.3 Creating a generic data structure with Sequence
9.3.1 Bags in action
9.3.2 Creating a BagIterator
9.3.3 Implementing AnyIterator
9.3.4 Implementing ExpressibleByArrayLiteral
9.3.5 Exercise
9.4 The Collection protocol
9.4.1 The Collection landscape
9.4.2 MutableCollection
9.4.3 RangeReplaceableCollection
9.4.4 BidirectionalCollection
9.4.5 RandomAccessCollection
9.5 Creating a collection
9.5.1 Creating a travel plan
9.5.2 Implementing Collection
9.5.3 Custom subscripts
9.5.4 ExpressibleByDictionaryLiteral
9.5.5 Exercise
9.6 Closing thoughts
Summary
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10 Understanding map, flatMap, and compactMap
10.1 Becoming familiar with map
10.1.1 Creating a pipeline with map
10.1.2 Mapping over a dictionary
10.1.3 Exercises
10.2 Mapping over sequences
10.2.1 Exercises
10.3 Mapping over optionals
10.3.1 When to use map on optionals
10.3.2 Creating a cover
10.3.3 A shorter map notation
10.3.4 Exercise
10.4 map is an abstraction
10.5 Grokking flatMap
10.5.1 What are the benefits of flatMap?
10.5.2 When map doesn’t cut it
10.5.3 Fighting the pyramid of doom
10.5.4 FlatMapping over an optional
10.6 flatMapping over collections
10.6.1 flatMapping over strings
10.6.2 Combining flatMap with map
10.6.3 Using compactMap
10.6.4 Nesting or chaining
10.6.5 Exercises
10.7 Closing thoughts
Summary
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11 Asynchronous error handling with Result
11.1 Why use the Result type?
11.1.1 Getting your hands on Result
11.1.2 Result is like Optional, with a twist
11.1.3 Understanding the benefits of Result
11.1.4 Creating an API using Result
11.1.5 Bridging from Cocoa Touch to Result
11.2 Propagating Result
11.2.1 Typealiasing for convenience
11.2.2 The search function
11.3 Transforming values inside Result
11.3.1 Exercise
11.3.2 flatMapping over Result
11.3.3 Exercises
11.4 Mixing Result with throwing functions
11.4.1 From throwing to a Result type
11.4.2 Converting a throwing function inside flatMap
11.4.3 Weaving errors through a pipeline
11.4.4 Finishing up
11.4.5 Exercises
11.5 Multiple errors inside of Result
11.5.1 Introducing AnyError
11.6 Impossible failure and Result
11.6.1 When a protocol defines a Result
11.7 Closing thoughts
Summary
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12 Protocol extensions
12.1 Class inheritance vs. Protocol inheritance
12.1.1 Modeling data horizontally instead of vertically.
12.1.2 Creating a protocol extension
12.1.3 Multiple extensions
12.2 Protocol inheritance vs. Protocol composition
12.2.1 When protocol inheritance is a tad rigid
12.2.2 Protocol inheritance
12.2.3 The composition approach
12.2.4 Unlocking the powers of an intersection
12.2.5 Exercises
12.3 Overriding priorities
12.3.1 Overriding a default implementation
12.3.2 Overriding with protocol inheritance
12.3.3 Exercise
12.4 Extending in two directions
12.4.1 Opting in to extensions
12.4.2 Exercises
12.5 Extending with associated types
12.5.1 A specialized extension
12.5.2 A wart in our extension
12.6 Extending with concrete constraints
12.7 Extending Sequence
12.7.1 Looking under the hood of filter
12.7.2 Creating the take(while:) method
12.7.3 Creating the Inspect method
12.7.4 Exercise
12.8 Closing thoughts
Summary
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13 Swift Patterns
13.1 Dependency injection
13.1.1 Swapping an implementation
13.1.2 Passing a custom Session
13.1.3 Constraining an associated type
13.1.4 Swapping an implementation
13.1.5 Unit testing and Mocking with associated types
13.1.6 Using the Result type
13.1.7 Exercise
13.2 Conditional conformance
13.2.1 Free functionality
13.2.2 Conditional conformance on associated types
13.2.3 Making Array conditionally conform to a custom protocol
13.2.4 Conditional conformance and generics
13.2.5 Conditional conformance on your types
13.2.6 Exercise
13.3 Dealing with protocol shortcomings
13.3.1 Avoiding a protocol using an enum
13.3.2 Type erasing a protocol
13.3.3 Exercise
13.4 An alternative to protocols
13.4.1 With great power comes great unreadability
13.4.2 Creating a generic struct
13.4.3 Rules of thumb for polymorphism
13.5 Closing thoughts
Summary
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14 Delivering quality Swift code
14.1 API documentation
14.1.1 How Quick Help works
14.1.2 Adding callouts to Quick Help
14.1.3 Documentation as HTML with Jazzy
14.2 Comments
14.2.1 Explain the why
14.2.2 Only explain obscure elements
14.2.3 Code has the truth
14.2.4 Comments are no band-aid to bad names
14.2.5 Zombie code
14.3 Settling on a style
14.3.1 Consistency is key
14.3.2 Enforcing rules with a linter
14.3.3 Installing Swift Lint
14.3.4 Configure SwiftLint
14.3.5 Temporarily disabling SwiftLint rules
14.3.6 Autocorrecting SwiftLint rules
14.3.7 Keeping SwiftLint in sync
14.4 Kill the Managers
14.4.1 The value of managers
14.4.2 Attacking managers
14.4.3 Paving the road for generics
14.5 Naming abstractions
14.5.1 Generic versus specific
14.5.2 Good names don’t change
14.5.3 Generic naming
14.6 Checklist
14.7 Closing thoughts
Answers
15 Where to Swift from here
15.1 Build frameworks that build on Linux
15.2 Explore the Swift Package Manager
15.3 Explore frameworks
15.4 Challenge yourself
15.4.1 Join the Swift evolution
15.4.2 Final words
About the Technology
It’s fun to create your first toy iOS or Mac app in Swift. Writing secure, reliable, professional-grade software is a different animal altogether. The Swift language includes an amazing set of high-powered features, and it supports a wide range of programming styles and techniques. You just have to roll up your sleeves and learn Swift in depth.
About the book
Swift in Depth guides you concept by concept through the skills you need to build professional software for Apple platforms, such as iOS and Mac; also on the server with Linux. By following the numerous concrete examples, enlightening explanations, and engaging exercises, you’ll finally grok powerful techniques like generics, efficient error handling, protocol-oriented programming, and advanced Swift patterns. Author Tjeerd in ’t Veen reveals the high-value, difficult-to-discover Swift techniques he’s learned through his own hard-won experience.
