override open func prepare() {
        guard let collectionView = collectionView else {
            return
        }
        

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Cognitive Complexity

Cognitive Complexity is a measure of how difficult a unit of code is to intuitively understand. Unlike Cyclomatic Complexity, which determines how difficult your code will be to test, Cognitive Complexity tells you how difficult your code will be to read and comprehend.

A method's cognitive complexity is based on a few simple rules:

• Code is not considered more complex when it uses shorthand that the language provides for collapsing multiple statements into one
• Code is considered more complex for each "break in the linear flow of the code"
• Code is considered more complex when "flow breaking structures are nested"

Further reading

• Cognitive Complexity docs
• Cognitive Complexity: A new way of measuring understandability

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terminating-newline

Verify that source files terminate with exactly one \n character. This ensures that the last line of the file is valid according to the POSIX standard. Also see No Newline at End of File for more information.

Swift source files should terminate with exactly 1 \n character, not 0 nor more than 1.

Preferred

let myConstant = 42¬
<eof></eof>

Not Preferred

let myConstant = 42<eof></eof>

let myConstant = 42¬
¬
¬
<eof></eof>

    }

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function-whitespace

Every function and method declaration should have one blank line before and after itself. An exception to this rule are functions that are declared at the start of a file (only need one blank line after their declaration) or at the end of a file (only need one blank line before their declaration). Comments immediately before a function declaration (no blank lines between them and the function) are considered to be part of the declaration.

Preferred

func function1() {
  var text = 1
  var text = 2
}

function1()

// a comment
func function2() {
  // something goes here
}

struct SomeStruct {

  func function3() {
    // something goes here
  }

  func function4() {
    // something else goes here
  };

}

func function5() {
  // something goes here
}

Not Preferred

func function1() {
  var text = 1
  var text = 2
}
function1()
// a comment
func function2() {
  // something goes here
}

struct SomeStruct {
  func function3() {
    // something goes here
  }

  func function4() {
    // something else goes here
  };
}
func function5() {
  // something goes here
}

        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: cellIdentifier, for: indexPath as IndexPath) as! ContentCollectionViewCell

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forced-type-cast

Avoid using the forced form of the type cast operator (as!) because Swift is not able to determine at compile time if the type conversion will succeed. In the event of an unsuccessful conversion, a runtime error will be triggered. The conditional form of the type cast operator (as?) is safer and should be used when possible.

Preferred

if let movie = item as? Movie {
    print("Movie: '\(movie.name)', dir. \(movie.director)")
}

Not Preferred

let movie = item as! Movie
print("Movie: '\(movie.name)', dir. \(movie.director)")

    }

Close

function-whitespace

Every function and method declaration should have one blank line before and after itself. An exception to this rule are functions that are declared at the start of a file (only need one blank line after their declaration) or at the end of a file (only need one blank line before their declaration). Comments immediately before a function declaration (no blank lines between them and the function) are considered to be part of the declaration.

Preferred

func function1() {
  var text = 1
  var text = 2
}

function1()

// a comment
func function2() {
  // something goes here
}

struct SomeStruct {

  func function3() {
    // something goes here
  }

  func function4() {
    // something else goes here
  };

}

func function5() {
  // something goes here
}

Not Preferred

func function1() {
  var text = 1
  var text = 2
}
function1()
// a comment
func function2() {
  // something goes here
}

struct SomeStruct {
  func function3() {
    // something goes here
  }

  func function4() {
    // something else goes here
  };
}
func function5() {
  // something goes here
}

    override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {

Close

function-whitespace

Every function and method declaration should have one blank line before and after itself. An exception to this rule are functions that are declared at the start of a file (only need one blank line after their declaration) or at the end of a file (only need one blank line before their declaration). Comments immediately before a function declaration (no blank lines between them and the function) are considered to be part of the declaration.

Preferred

func function1() {
  var text = 1
  var text = 2
}

function1()

// a comment
func function2() {
  // something goes here
}

struct SomeStruct {

  func function3() {
    // something goes here
  }

  func function4() {
    // something else goes here
  };

}

func function5() {
  // something goes here
}

Not Preferred

func function1() {
  var text = 1
  var text = 2
}
function1()
// a comment
func function2() {
  // something goes here
}

struct SomeStruct {
  func function3() {
    // something goes here
  }

  func function4() {
    // something else goes here
  };
}
func function5() {
  // something goes here
}

    }

Close

function-whitespace

Every function and method declaration should have one blank line before and after itself. An exception to this rule are functions that are declared at the start of a file (only need one blank line after their declaration) or at the end of a file (only need one blank line before their declaration). Comments immediately before a function declaration (no blank lines between them and the function) are considered to be part of the declaration.

Preferred

func function1() {
  var text = 1
  var text = 2
}

function1()

// a comment
func function2() {
  // something goes here
}

struct SomeStruct {

  func function3() {
    // something goes here
  }

  func function4() {
    // something else goes here
  };

}

func function5() {
  // something goes here
}

Not Preferred

func function1() {
  var text = 1
  var text = 2
}
function1()
// a comment
func function2() {
  // something goes here
}

struct SomeStruct {
  func function3() {
    // something goes here
  }

  func function4() {
    // something else goes here
  };
}
func function5() {
  // something goes here
}

    override open var collectionViewContentSize : CGSize {

Close

colon-whitespace

There should be no whitespace preceding the colon, exactly one whitespace after the colon for: * var, class, struct, protocol, extension, func, and tuple declarations * dict literals and types * case statements

However, for conditional expressions there should be a single whitespace before and after the colon.

Variable declarations

Preferred

var x: Int = 2

Not Preferred

var x : Int
var y:   String

Dictionary literals and types

Preferred

var x = [ 'key1': 1, 'key2': 2 ]
var y: [ Int: String ]

Not Preferred

var x = [ 'key1' : 1, 'key2':  3]
var y: [ Int :    String ]

Case statements

Preferred

switch character {
case "a": doSomething(a);
default: alert();
}

Not Preferred

switch character {
case "a" : doSomething(a);
default:     alert();
}

Class, Struct, Protocol, and Extension declarations

Preferred

class ClassName: BaseClass {
}

struct StructName: BaseStruct {
}

protocol ProtocolName: AnotherProtocol {
}

extension TypeName: ProtocolName {
}

Not Preferred

class ClassName : BaseClass {
}

struct StructName:  BaseStruct {
}

protocol ProtocolName:AnotherProtocol {
}

extension TypeName : ProtocolName {
}

Tuple declarations

Preferred

var y = (key: 1, value: 2)

Not Preferred

var y = (key:1, value : 2)

Function declarations

Preferred

func someFunction<t: someclass u: someprotocol>(someT: T, someU: U) {
}</t:>

Not Preferred

func someFunction<t : someclass u:someprotocol>(someT: T, someU: U) {
}</t>

Conditional expressions

Preferred

var x = condition ? a : b

Not Preferred

var x = condition ? a: b
var x = condition ? a   : b