我有以下类，用init方法：
class user {
var name:String
var address:String
init(nm: String,ad: String) {
name = nm
address = ad
}
}
我试图子类这个类，但我不断收到的错误super.init()部分：
class registeredUser : user {
var numberPriorVisits: Int
// This is where things start to go wrong - as soon as I type 'init' it
// wants to autocomplete it for me with all of the superclass' arguments,// and I'm not sure if those should go in there or not:
init(nm: String,ad: String) {
// And here I get errors:
super.init(nm: String,ad: String)
// etc....
苹果的iBook有子类化的例子，但没有一个特性类有一个init()方法与任何实际参数。所有的初始化都没有参数。
那么，你怎么做呢？
除了Chuck的答案，你还必须在调用super.init之前初始化你的新引入的属性
A designated initializer must ensure that all of the properties
introduced by its class are initialized before it delegates up to a
superclass initializer. (The Swift Programming Language -> Language Guide -> Initialization)
因此，使它工作：
init(nm: String,ad: String) {
numberPriorVisits = 0
super.init(nm: nm,ad: ad)
}
这个简单的初始化为零可以通过将属性的默认值设置为零来完成。也鼓励这样做：
var numberPriorVisits: Int = 0
如果你不想要这样的默认值，那么扩展你的初始化器也为新的属性设置一个新的值是有意义的：
init(name: String,ads: String,numberPriorVisits: Int) {
self.numberPriorVisits = numberPriorVisits
super.init(nm: name,ad: ads)
}
