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swiftreturndependent-type

Can Swift structs self-delete?

Consider the following:

struct MiniString {
    private(set) var value: String

    init(_ value: String) {
        if value.count < 17 {
            self.value = value
        } else {
            selfDeleteSomehow()
        }
    }
}

Elsewhere this could be instantiated thus:

var ms: MiniString? = MiniString("This string is too long to be accepted")
print(ms) // prints 'nil'

Context: my specific use-case is for a func declaration in a protocol that would return a Double between 0.0 and 1.0, but no higher or lower, something like:

protocol DoubleBetweenZeroAndOneProtocol {
    func getResult() -> DoubleBetweenZeroAndOne
}
Solution

  • You could use a failable initializer:

    struct MiniString {

    var value: String { return value_ }

    private let value_: String

    init?(_ seedValue: String) {
        if seedValue.count < 17 {
            value_ = seedValue
        } else {
            return nil
        }
    }
}