This question already has answers here:
Noop for Swift's Exhaustive Switch Statements
(8 answers)
Closed 5 years ago.
I have question, i have enum with 3 state. On 2 of 3 that state i want to do something, but for 3rd i do not. However, when i do not put block of code below case, compiler highligh it with red and won't allow me to run app. Example:
func leftBarButtonTappedWithType(type: CustomNavBarViewModel.LeftBarButtonType) {
switch type {
case .none:
print("")
case .back:
self.popViewController(animated: true)
case .hamburger:
self.func()
}
}
You can see that for case .none i wrote print("") because in other case i won't be able to compile. How to avoid that? Kind of ugly.
Just get your function to return in that case:
case .hamburger:
return
Hope that helps.
Per the discussion and #MartinR 's comment, break is probably a better general solution to exit the switch statement.
Related
This question already has an answer here:
Testing for enum value fails if one has associated value?
(1 answer)
Closed 7 years ago.
enum ConditionType {
case Normal
case Sick
case Plagued
case Poisoned(Double)
case Drunk(Double)
case Healing(Double)
case Starving
case NearDeath(Double)
case Sleepy
}
var conditions: [ConditionType]
func addCondition(condition: ConditionType) {
if conditions.contains(condition) == false {
conditions.append(condition)
}
}
In the "if conditions.contains(condition) == false {" line above I am getting the following error:
Cannot invoke 'contains' with an argument list of '(ConditionType)'. What is the deal here? If I remove the associated values from the enum elements, then it compiles just fine.
I am running XCode 7.0 Beta 3.
You need to make ConditionType equatable and crate an op== that explains whether just the types need to match for them to be the same or if the contained values also need to match.
This question already has answers here:
Switch in Swift - Case label in a switch should have at least one executable statement
(2 answers)
Noop for Swift's Exhaustive Switch Statements
(8 answers)
Closed 7 years ago.
Here is my code:
enum GameScreen
{
case kSceneFlashScreen
case kSceneMainMenu
case kSceneGameScreen
case kSceneStoreScreen
case kSceneGameOver
}
class YSGameManager: NSObject {
func replaceGameScene(inScreen: GameScreen)
{
switch inScreen
{
case GameScreen.kSceneGameScreen: //Error for here
case GameScreen.kSceneMainMenu : //here also error
}
}
}
Eror LOG: 'case' label in a 'switch' should have at least one executable statement
How to use enum in switch case in Swift ?
There's an error because you haven't got anything after : and before the next case. To solve this you can:
1. Add some code to do something.
2. Add fallthrough if you want to move to the next case. This may have been what you were trying to do. However, in Swift, switch statements don't fallthrough by default to the next case, they break.
3. Add break to stop the switch statement.
It’s complaining that you need to actually do something after the matching case. Otherwise there’s not much point matching it, and chances are it’s a typo.
Other possibly than coverage i.e. if you don’t want a default, you want to name every possible enum, even though you don’t want to do anything for some of them. In which case, stick in a break:
switch inScreen {
case kSceneGameScreen:
break
// etc.
}
Note, there’s no implicit fall through in Swift’s switch statements. You need to give one explicitly:
switch inScreen {
case kSceneGameScreen:
// do a game-screen-specific thing
fallthrough // then
case kSceneMainMenu:
// do a thing for both
// kSceneGameScreen and kSceneMainMenu
// etc.
}
But if you just want to match two possibilities, you don’t need to use fall through, you can just combine them with ,:
switch inScreen {
case kSceneGameScreen, kSceneMainMenu:
// do a thing for both
// kSceneGameScreen and kSceneMainMenu
// etc.
}
This question already has answers here:
Noop for Swift's Exhaustive Switch Statements
(8 answers)
Closed 8 years ago.
Compiler complain about the lack of at least one executable statement on case label in a switch :
switch someData {
case .one:
// No statements
// Error occurs here
case .two:
// Some statements here
default:
// Some statements here
}
Here is the exact message:
'case' label in a 'switch' should have at least one executable statement
So is there any statement that do nothing to satisfy compiler requirement?
I know a simple statement like print() can do the job but I wonder if there is a specific one?
In other language, Ada for example there is a nullstatement to achieve this.
Set break or return, depending on what you want to do.
switch someData {
case .one:
nil
case .two:
// Some statements here
default:
// Some statements here
}
I know that the keyword "pass" in Python will allow one to leave a line of code empty where it should have contained an executable statement. Is there a similar keyword in Swift?
I am using a switch statement and Swift requires there to be a default case. The code should reach the default statement most of the time and I want nothing to be done in this case.
You can break out of the default case. Swift just wants you to be explicit about that to avoid bugs.
Here's a simple example:
enum Food {
case Banana
case Apple
case ChocolateBar
}
func warnIfUnhealthy(food : Food) {
switch food {
case .ChocolateBar:
println("Don't eat it!")
default:
break
}
}
let candy = Food.ChocolateBar
warnIfUnhealthy(candy)
The proper way to add a catch-all without an action to a switch statement is to add
default: break
at the end.
Swift requires exhaustive switch statements, and that each case have executable code.
'case' label in a 'switch' should have at least one executable statement
Has anybody settled on a good way to handle the cases where you don't want to actually do anything? I can put a println() in there, but that feels dirty.
According to the book, you need to use break there:
The scope of each case can’t be empty. As a result, you must include at least one statement following the colon (:) of each case label. Use a single break statement if you don’t intend to execute any code in the body of a matched case.
You can use a break statement:
let vegetable = "red pepper"
var vegetableComment: String = "Nothing"
switch vegetable {
case "cucumber", "watercress":
break // does nothing
case let x where x.hasSuffix("pepper"):
vegetableComment = "Is it a spicy \(x)?"
default:
vegetableComment = "Everything tastes good in soup."
}
Example modified from the docs
Below is one option for null statement, but maybe not a good solution. I cannot find a statement like python pass
{}()
for switch case, break is better choice.
break
Do nothing in exhaustive switch case statements:
Swift:
switch yourVariable {
case .someCase:
break
}
SwiftUI:
switch yourVariable {
case .someCase:
EmptyView() // break does not work with ViewBuilder
}
Using EmptyView() instead of break in SwiftUI views prevents the error:
Closure containing control flow statement cannot be used with function
builder ViewBuilder.
EmptyView() is a SwiftUI standard view (tested with Xcode 12, iOS 14) and does not need to be defined yourself.
In addition to break mentioned in other answers, I have also seen () used as a no-op statement:
switch 0 == 1 {
case true:
break
case false:
()
}
Use () if you find break confusing or want to save 3 characters.
The cleanest solution I've found is to simply include your last statement in the switch case as your default. This avoids the need to add break or other unnecessary statements while still covering all possible cases.
For example:
switch myVar {
case 0:
myOtherVar = "Red"
case 1:
myOtherVar = "Blue"
default:
myOtherVar = "Green"
}
You can check specific case, no need to be exhustive with switch cases
Say you have a enum like this,
enum Selection {
case one
case two
case three
}
var myCase = Selection.one
you can check like this,
if case .one = myCase {
print("one")
}
A clean solution I use for my default case is:
default: ()