Swift 3 focused on solidifying and maturing the Swift language and development experience. It focused on several areas:
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API design guidelines: The way in which Swift is used in popular libraries has almost as much of an effect on the character of Swift code as the Swift language itself. The API naming and design guidelines are a carefully crafted set of guidelines for building great Swift APIs.
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Automatic application of naming guidelines to imported Objective-C APIs: When importing Objective-C APIs, the Swift 3 compiler automatically maps methods into the new Swift 3 naming guidelines, and provides a number of Objective-C features to control and adapt this importing.
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Adoption of naming guidelines in key APIs: The Swift Standard Library has been significantly overhauled to embrace these guidelines, and key libraries like Foundation and libdispatch have seen major updates, which provide the consistent development experience we seek.
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Swiftification of imported Objective-C APIs: Beyond the naming guidelines, Swift 3 provides an improved experience for working with Objective-C APIs. This includes importing Objective-C generic classes, providing the ability to import C APIs into an "Object Oriented" style, much nicer imported string enums, safer syntax to work with selectors and keypaths, etc.
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Focus and refine the language: Since Swift 3 is the last release to make major source breaking changes, it is also the right release to reevaluate the syntax and semantics of the core language. This means that some obscure or problematic features will be removed, we focus on improving consistency of syntax in many small ways (e.g. by revising handling of parameter labels, and focus on forward looking improvements to the type system. This serves the overall goal of making Swift a simpler, more predictable, and more consistent language over the long term.
Swift 3 is the first release to enable broad scale adoption across multiple platforms, including significant functionality in the Swift core libraries (Foundation, libdispatch, XCTest, etc), portability to a number of platforms including Linux/x86, Raspberry Pi, and Android, and the Swift package manager to easily manage the distribution of Swift soure code.
Finally, Swift 3 also includes a mix of relatively small but important additions to the language and standard library that make solving common problems easier and make everything feel nicer.
- SE-0002: Removing currying
funcdeclaration syntax - SE-0003: Removing
varfrom Function Parameters - SE-0004: Remove the
++and--operators - SE-0005: Better Translation of Objective-C APIs Into Swift
- SE-0006: Apply API Guidelines to the Standard Library
- SE-0007: Remove C-style for-loops with conditions and incrementers
- SE-0008: Add a Lazy flatMap for Sequences of Optionals
- SE-0016: Adding initializers to Int and UInt to convert from UnsafePointer and UnsafeMutablePointer
- SE-0017: Change
Unmanagedto useUnsafePointer - SE-0019: Swift Testing
- SE-0023: API Design Guidelines
- SE-0025: Scoped Access Level
- SE-0029: Remove implicit tuple splat behavior from function applications
- SE-0031: Adjusting inout Declarations for Type Decoration
- SE-0032: Add
first(where:)method toSequenceType - SE-0033: Import Objective-C Constants as Swift Types
- SE-0034: Disambiguating Line Control Statements from Debugging Identifiers
- SE-0035: Limiting
inoutcapture to@noescapecontexts - SE-0036: Requiring Leading Dot Prefixes for Enum Instance Member Implementations
- SE-0037: Clarify interaction between comments & operators
- SE-0038: Package Manager C Language Target Support
- SE-0039: Modernizing Playground Literals
- SE-0040: Replacing Equal Signs with Colons For Attribute Arguments
- SE-0043: Declare variables in 'case' labels with multiple patterns
- SE-0044: Import as Member
- SE-0046: Establish consistent label behavior across all parameters including first labels
- SE-0047: Defaulting non-Void functions so they warn on unused results
- SE-0048: Generic Type Aliases
- SE-0049: Move @noescape and @autoclosure to be type attributes
- SE-0052: Change IteratorType post-nil guarantee
- SE-0053: Remove explicit use of
letfrom Function Parameters - SE-0054: Abolish
ImplicitlyUnwrappedOptionaltype - SE-0055: Make unsafe pointer nullability explicit using Optional
- SE-0057: Importing Objective-C Lightweight Generics
- SE-0059: Update API Naming Guidelines and Rewrite Set APIs Accordingly
- SE-0060: Enforcing order of defaulted parameters
- SE-0061: Add Generic Result and Error Handling to autoreleasepool()
- SE-0062: Referencing Objective-C key-paths
- SE-0063: SwiftPM System Module Search Paths
- SE-0064: Referencing the Objective-C selector of property getters and setters
- SE-0065: A New Model For Collections and Indices
- SE-0066: Standardize function type argument syntax to require parentheses
- SE-0067: Enhanced Floating Point Protocols
- SE-0069: Mutability and Foundation Value Types
- SE-0070: Make Optional Requirements Objective-C-only
- SE-0071: Allow (most) keywords in member references
- SE-0072: Fully eliminate implicit bridging conversions from Swift
- SE-0076: Add overrides taking an UnsafePointer source to non-destructive copying methods on UnsafeMutablePointer
- SE-0077: Improved operator declarations
- SE-0081: Move
whereclause to end of declaration - SE-0085: Package Manager Command Names
- SE-0086: Drop NS Prefix in Swift Foundation
- SE-0088: Modernize libdispatch for Swift 3 naming conventions
- SE-0089: Renaming
String.init<T>(_: T) - SE-0091: Improving operator requirements in protocols
- SE-0092: Typealiases in protocols and protocol extensions
- SE-0093: Adding a public
baseproperty to slices - SE-0094: Add sequence(first:next:) and sequence(state:next:) to the stdlib
- SE-0095: Replace
protocol<P1,P2>syntax withP1 & P2syntax - SE-0096: Converting dynamicType from a property to an operator
- SE-0099: Restructuring Condition Clauses
- SE-0101: Reconfiguring
sizeofand related functions into a unifiedMemoryLayoutstruct - SE-0102: Remove
@noreturnattribute and introduce an emptyNevertype - SE-0103: Make non-escaping closures the default
- SE-0106: Add a
macOSAlias for theOSXPlatform Configuration Test - SE-0107: UnsafeRawPointer API
- SE-0109: Remove the
Booleanprotocol - SE-0111: Remove type system significance of function argument labels
- SE-0112: Improved NSError Bridging
- SE-0113: Add integral rounding functions to FloatingPoint
- SE-0114: Updating Buffer "Value" Names to "Header" Names
- SE-0115: Rename Literal Syntax Protocols
- SE-0116: Import Objective-C
idas SwiftAnytype - SE-0117: Allow distinguishing between public access and public overridability
- SE-0118: Closure Parameter Names and Labels
- SE-0120: Revise
partitionMethod Signature - SE-0121: Remove
OptionalComparison Operators - SE-0124:
Int.init(ObjectIdentifier)andUInt.init(ObjectIdentifier)should have abitPattern:label - SE-0125: Remove
NonObjectiveCBaseandisUniquelyReferenced - SE-0127: Cleaning up stdlib Pointer and Buffer Routines
- SE-0128: Change failable UnicodeScalar initializers to failable
- SE-0129: Package Manager Test Naming Conventions
- SE-0130: Replace repeating
CharacterandUnicodeScalarforms of String.init - SE-0131: Add
AnyHashableto the standard library - SE-0133: Rename
flatten()tojoined() - SE-0134: Rename two UTF8-related properties on String
- SE-0135: Package Manager Support for Differentiating Packages by Swift version
- SE-0136: Memory Layout of Values
- SE-0137: Avoiding Lock-In to Legacy Protocol Designs