Cyclomatic Complexity Violation: Function should have complexity 10 or less: currently complexity equals 13 (cyclomatic_complexity)

Question

I have the following code in swift3 and i am using swift lint for linting the code. The code is given as follows:

    func selectedMenuInLoggedOutState(sender: UIButton) {
    switch sender.tag {
    case 1:
      if let menu = LeftGuestMenu(rawValue: 0) {
        self.changeGuestViewController(menu)
      }
    case 2:
      if let menu = LeftGuestMenu(rawValue: 1) {
        self.changeGuestViewController(menu)
      }
    case 3:
      if let menu = LeftGuestMenu(rawValue: 2) {
        self.changeGuestViewController(menu)
      }
    case 4:
      if let menu = LeftGuestMenu(rawValue: 3) {
        self.changeGuestViewController(menu)
      }
    case 5:
      if let menu = LeftGuestMenu(rawValue: 4) {
        self.changeGuestViewController(menu)
      }
    case 6:
      if let menu = LeftGuestMenu(rawValue: 5) {
        self.changeGuestViewController(menu)
      }
    default:
      break
    }
  }

The swift lint generates a "Cyclomatic Complexity Violation" warning. Why did this warning occur and how does one resolve it?

Jakub Truhlář · Answer 1 · 2018-12-10T16:09:48.527

59

The method is too complex. But instead of rewriting the code, you could exclude switches from the cyclomatic_complexity calculation (since they are perfectly readable) like this:

cyclomatic_complexity:
  ignores_case_statements: true

edited Dec 10 '18 at 16:09

answered Jul 07 '18 at 09:56

Jakub Truhlář

20,070
9
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2

I like this solution. I do not want to change my case statements. – Ariel Antonio Fundora Feb 12 '19 at 16:17
how do you discover the options provided by a linter rule? – wfbarksdale Mar 27 '19 at 23:43
If you type run `swiftlint rules` it will list all the current rules for your project - the last column should contain the options. – deanWombourne May 01 '19 at 09:46

Daniel T. · Accepted Answer · 2017-08-26T00:17:34.767

23

The warning occurs because your function is too complex as defined by the metric which essentially counts the number of decisions that need to be made.

A simple way to avoid it in this particular case would be with some simple math:

func selectedMenuInLoggedOutState(sender: UIButton) {
    guard let menu = LeftGuestMenu(rawValue: sender.tag - 1) else { return }
    self.changeGuestViewController(menu)
}

edited Aug 26 '17 at 00:17

answered Aug 25 '17 at 23:48

Daniel T.

32,821
6
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Yea, a strong argument can be made that CC should ignore switch/case statements and only count if statements. – Daniel T. Aug 25 '17 at 23:51
I agree; there is a big difference between a switch and a bunch of `if/elseif/else` statements – Paulw11 Aug 25 '17 at 23:51
@DanielT. So should i replace the whole switch statement with the single line code that you gave? – Chelsea Shawra Aug 25 '17 at 23:55
2

On reflection, I don't think the "math" solution is so bad in this case. You can use it or try my simplified switch; which ever you like – Paulw11 Aug 25 '17 at 23:58
I updated with a guard statement to protect against bad tags. Yes @ChelseaShawra, you can replace the whole function with this simpler code. – Daniel T. Aug 26 '17 at 00:18
Why do your UIButton tags start at 1 rather than 0 anyway? – William GP Aug 14 '19 at 22:58
@WilliamGP there's a deeper question here of why anyone would use tags at all in UIViews but ‍♂️ – Fogmeister Aug 10 '23 at 17:10

score 19 · Answer 3 · answered May 01 '19 at 09:48

You can disable swiftlint warnings in code like this:

// swiftlint:disable cyclomatic_complexity
func selectedMenuInLoggedOutState(sender: UIButton) {
    ...
}
// swiftlint:enable cyclomatic_complexity

or, if you want to explicitly just disable the next swiftlint warning:

// swiftlint:disable:next cyclomatic_complexity
func selectedMenuInLoggedOutState(sender: UIButton) {

Paulw11 · Answer 4 · 2017-08-26T00:12:14.850

2

You can reduce your complexity by eliminating the repeated if let statements:

func selectedMenuInLoggedOutState(sender: UIButton) {

    let menu: MenuType?

    switch sender.tag {
    case 1:
     menu = LeftGuestMenu(rawValue: 0)
    case 2:
     menu = LeftGuestMenu(rawValue: 1) 
    case 3:
     menu = LeftGuestMenu(rawValue: 2) 
    case 4:
      menu = LeftGuestMenu(rawValue: 3) 
    case 5:
      menu = LeftGuestMenu(rawValue: 4)   
    case 6:
      menu = LeftGuestMenu(rawValue: 5) 
    default:
      menu=nil
    }

    if let menu = menu {
       self.changeGuestViewController(menu)
    }
  }

edited Aug 26 '17 at 00:12

answered Aug 25 '17 at 23:55

Paulw11

108,386
14
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it shows the error constant menu used before being initialised – Chelsea Shawra Aug 26 '17 at 00:03
1

This code has a CC of 8 which avoids the warning, but just barely. :-) – Daniel T. Aug 26 '17 at 00:21

score 2 · Answer 5 · answered Sep 01 '17 at 10:58

In case if you don't want to change your logic, follow below. Add "cyclomatic_complexity:" property and set warning value in .swiftlint.yml file.

cyclomatic_complexity: warning: 25

Note: Here setting warning value means, increasing the number of linearly independent paths. You can set your own value.

Cyclomatic Complexity Violation: Function should have complexity 10 or less: currently complexity equals 13 (cyclomatic_complexity)

5 Answers5