swift2guard-statement

How to use guard outside of function?


Is it possible to use guard outside of a function?

The following throws an error that return or break needs to be used but that isn't possible in this case.

var var1 = String?()
guard let validVar = var1 else {
    print("not nil")
}

Solution

  • No its not possible. To instanciate variables with knowledge of other variables in the class, you can use lazy initialisation or getter.

    var testString : String?
    lazy var testString2 : String = {
         guard let t = self.testString else { return String()}
          return t
    }()
    

    if iam wrong feel free to correct me :)

    guard is made for robustness of functions i think, and will do a break in the function if the conditions are wrong. So if you really need this variable it has to be meet the conditions. Like an if let but more clean :)

    From your example: var testString = String?() is invalid. Instantiate an String will never be nil so no optional is requiert.

    Edit: I wrote an example in my Playground.

    import UIKit
    
    var var1 : String?
    
    var validVar : String = {
        guard let validVar = var1 else {
            print("not nil")
            return "NIL"
        }
        return validVar
    }()
    
    print("\(validVar)")