使用泛型类时 Swift 抛出运行时错误

Question

似乎 swift 在处理泛型类时存在一些问题。似乎这些代码可以编译，但在遇到 println(act.actId) 时会出现运行时错误。它抛出了一个EXC_BAD_ACCESS错误。

对于这个问题还有其他方法或解决方法吗？

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)

Answer 1

就我而言，这不会在 Playground 上编译。

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

您需要将 init() 标记为 required

我已经改变了它，现在它可以工作了

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)

参见similar question了解更多详情