Attributes

Attributes should be on their own lines in functions and types, but on the same line as variables and imports

• Identifier: attributes
• Enabled by default: No
• Supports autocorrection: No
• Kind: style
• Analyzer rule: No
• Minimum Swift compiler version: 5.0.0
• Default configuration:

  Key	Value
  severity	warning
  attributes_with_arguments_always_on_line_above	true
  always_on_same_line	[“@IBAction”, “@NSManaged”]
  always_on_line_above	[]

Rationale

Erica Sadun says:

My take on things after the poll and after talking directly with a number of developers is this: Placing attributes like @objc, @testable, @available, @discardableResult on their own lines before a member declaration has become a conventional Swift style.

This approach limits declaration length. It allows a member to float below its attribute and supports flush-left access modifiers, so internal, public, etc appear in the leftmost column. Many developers mix-and-match styles for short Swift attributes like @objc

See https://ericasadun.com/2016/10/02/quick-style-survey/ for discussion.

SwiftLint’s rule requires attributes to be on their own lines for functions and types, but on the same line for variables and imports.

Non Triggering Examples

@objc var x: String

@objc private var x: String

@nonobjc var x: String

@IBOutlet private var label: UILabel

@IBOutlet @objc private var label: UILabel

@NSCopying var name: NSString

@NSManaged var name: String?

@IBInspectable var cornerRadius: CGFloat

@available(iOS 9.0, *)
 let stackView: UIStackView

@NSManaged func addSomeObject(book: SomeObject)

@IBAction func buttonPressed(button: UIButton)

@objc
 @IBAction func buttonPressed(button: UIButton)

@available(iOS 9.0, *)
 func animate(view: UIStackView)

@available(*, deprecated, message: "A message")
 func animate(view: UIStackView)

@nonobjc
 final class X {}

@available(iOS 9.0, *)
 class UIStackView {}

@NSApplicationMain
 class AppDelegate: NSObject, NSApplicationDelegate {}

@UIApplicationMain
 class AppDelegate: NSObject, UIApplicationDelegate {}

@IBDesignable
 class MyCustomView: UIView {}

@testable import SourceKittenFramework

@objc(foo_x)
 var x: String

@available(iOS 9.0, *)
@objc(abc_stackView)
 let stackView: UIStackView

@objc(abc_addSomeObject:)
 @NSManaged func addSomeObject(book: SomeObject)

@objc(ABCThing)
 @available(iOS 9.0, *)
 class Thing {}

class Foo: NSObject {
 override var description: String { return "" }
}

class Foo: NSObject {

 override func setUp() {}
}

@objc
class ⽺ {}

extension Property {

    @available(*, unavailable, renamed: "isOptional")
    public var optional: Bool { fatalError() }
}

@GKInspectable var maxSpeed: Float

@discardableResult
 func a() -> Int

@objc
 @discardableResult
 func a() -> Int

func increase(f: @autoclosure () -> Int) -> Int

func foo(completionHandler: @escaping () -> Void)

private struct DefaultError: Error {}

@testable import foo

private let bar = 1

import XCTest
@testable import DeleteMe

@available (iOS 11.0, *)
class DeleteMeTests: XCTestCase {
}

@objc
internal func foo(identifier: String, completion: @escaping (() -> Void)) {}

@objc
internal func foo(identifier: String, completion: @autoclosure (() -> Bool)) {}

func printBoolOrTrue(_ expression: @autoclosure () throws -> Bool?) rethrows {
  try print(expression() ?? true)
}

import Foundation

class MyClass: NSObject {
  @objc(
    first:
  )
  static func foo(first: String) {}
}

func refreshable(action: @escaping @Sendable () async -> Void) -> some View {
    modifier(RefreshableModifier(action: action))
}

import AppKit

@NSApplicationMain
@MainActor
final class AppDelegate: NSAppDelegate {}

Triggering Examples

@objc
 ↓var x: String

@objc

 ↓var x: String

@objc
 private ↓var x: String

@nonobjc
 ↓var x: String

@IBOutlet
 private ↓var label: UILabel

@IBOutlet

 private ↓var label: UILabel

@NSCopying
 ↓var name: NSString

@NSManaged
 ↓var name: String?

@IBInspectable
 ↓var cornerRadius: CGFloat

@available(iOS 9.0, *) ↓let stackView: UIStackView

@NSManaged
 ↓func addSomeObject(book: SomeObject)

@IBAction
 ↓func buttonPressed(button: UIButton)

@IBAction
 @objc
 ↓func buttonPressed(button: UIButton)

@available(iOS 9.0, *) ↓func animate(view: UIStackView)

@nonobjc final ↓class X {}

@available(iOS 9.0, *) ↓class UIStackView {}

@available(iOS 9.0, *)
 @objc ↓class UIStackView {}

@available(iOS 9.0, *) @objc
 ↓class UIStackView {}

@available(iOS 9.0, *)

 ↓class UIStackView {}

@UIApplicationMain ↓class AppDelegate: NSObject, UIApplicationDelegate {}

@IBDesignable ↓class MyCustomView: UIView {}

@testable
↓import SourceKittenFramework

@testable


↓import SourceKittenFramework

@available(iOS 9.0, *) @objc(abc_stackView)
 ↓let stackView: UIStackView

@objc(abc_addSomeObject:) @NSManaged
 ↓func addSomeObject(book: SomeObject)

@objc(abc_addSomeObject:)
 @NSManaged
 ↓func addSomeObject(book: SomeObject)

@available(iOS 9.0, *)
 @objc(ABCThing) ↓class Thing {}

@GKInspectable
 ↓var maxSpeed: Float

@discardableResult ↓func a() -> Int

@objc
 @discardableResult ↓func a() -> Int

@objc

 @discardableResult
 ↓func a() -> Int