Swift throw run time error when using generic class

Question

Seems swift has some problems when it deal with generic class. Seems these code can be compiled but will have run time error when meet println(act.actId). It throw out a EXC_BAD_ACCESS bug.

Is there any other way or workaround about this issue?

public class Item {
    public var id: String
    public init(str: String) {
        id = str
    }
}

public class Account: Item {
    public var actId: String
    public override init(str: String) {
        actId = "antId: \(str)"
        super.init(str: str)
    }
}

public class Keyword: Item {
    public var keywordId: String
    public override init(str: String) {
        keywordId = "keywordId: \(str)"
        super.init(str: str)
    }

}

public class Creator<T: Item> {
    public func parse(str: String) -> T {
        var result: T = T(str: str)
        return result
    }
}

var a = Creator<Account>()
var act = a.parse("Apple")
println(act.actId)

score 0 · Answer 1 · edited May 23 '17 at 11:58

In my case, this doesn't compile in playground.

Subclasses do not inherit their superclass initializers by default -> Apple

You need marking init() as required

I've changed it and it works now

public class Item {
    public var id: String
    public required init(str: String) {
        id = str
    }
}

public class Account: Item {
    public var actId: String
    public required init(str: String) {
        actId = "antId: \(str)"
        super.init(str: str)
    }
}

public class Keyword: Item {
    public var keywordId: String
    public required init(str: String) {
        keywordId = "keywordId: \(str)"
        super.init(str: str)
    }

}

public class Creator<T: Item> {
    public func parse(str: String) -> T {
        let result: T = T(str: str)
        return result
    }
}

var a = Creator<Account>()
var act = a.parse("Apple")
print(act.actId)

See similar question for more details

Swift throw run time error when using generic class

1 Answers1