我有两个类,Shape和Square
class Shape { var numberOfSides = 0 var name: String init(name:String) { self.name = name } func simpleDescription() -> String { return "A shape with \(numberOfSides) sides." } } class Square: Shape { var sideLength: Double init(sideLength:Double,name:String) { super.init(name:name) // Error here self.sideLength = sideLength numberOfSides = 4 } func area () -> Double { return sideLength * sideLength } }
使用上面的实现我得到错误:
property 'self.sideLength' not initialized at super.init call super.init(name:name)
为什么我必须在调用super.init之前设置self.sideLength?
报价从Swift编程语言,它回答你的问题:
“Swift’s compiler performs four helpful safety-checks to make sure
that two-phase initialization is completed without error:”Safety check 1 “A designated initializer must ensure that all of the
“properties introduced by its class are initialized before it
delegates up to a superclass initializer.”Excerpt From: Apple Inc. “The Swift Programming Language.” iBooks. 07000
版权声明:本文内容由互联网用户自发贡献,该文观点与技术仅代表作者本人。本站仅提供信息存储空间服务,不拥有所有权,不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容, 请发送邮件至 dio@foxmail.com 举报,一经查实,本站将立刻删除。