initializer

When __new__ return instance of class, everything is ok, we can create subclass with no problems: class A: def __new__(cls, p1, p2): self = object.__new__(cls) return self def __init__(self, p1, p2): self.p1 = p1 self.p2 = p2 class B(A): def __new__(cls, p3): self = super().__new__(cls, 1, 2) return self def __init__(self, p3): super().__init__(1, 2) self.p3 = p3 a = A(1, 2) print(a.p2) # output: 2 b = B(3) print(b.p3) # output: 3 But, If __new__() does not return an instance of cls , then the new instance’s __init__() method will not be invoked. Looks like we have to call __init__() inside _

I have a class for a linked list declared like this: class LinkedNode<T> { let data: T var next: LinkedNode<T>? func traverseList(process: (LinkedNode<T>) -> ()) { ... } } What I want to do is extend Array to have an initialiser that converts my LinkedNode class to an array of linked nodes. I tried this: extension Array where Element == LinkedNode<T> { init(node: LinkedNode<T>) { var result = [LinkedNode<T>]() traverseList { result.append($0) } return result } } But that gives errors that T is undeclared. I have tried taking it out and doing other things, but nothing has worked. I was able to

发现swift和java有一个完全不一样的地方 在swift中, 子类必须先初始化子类的所有属性, 然后才能调用父类的构造器. 而在java中.super调用必须出现在构造函数的第一行. java代码 public class Dog { String name; Dog(String name){ this.name = name; } } class NoisyDog extends Dog { int age; NoisyDog(String name) { // 交换以下两行的顺序会报错: Constructor call must be the first statement in a constructor super(name); this.age = 5; } } 对应的swift代码: class Dog { var name: String; init(name: String){ self.name = name; } } class NoisyDog: Dog { var age: Int override init(name: String) { //交换以下两行的顺序会报错error: property 'self.age' not initialized at super.init call self.age = 5; super.init(name:

For example, doing something like this: foreach (DataRow row in data.Rows) { Person newPerson = new Person() { Id = row.Field<int>("Id"), Name = row.Field<string>("Name"), LastName = row.Field<string>("LastName"), DateOfBirth = row.Field<DateTime>("DateOfBirth") }; people.Add(newPerson); } Setting a breakpoint to an individual assignation is not possible, the breakpoint is set to the entire block. If I want to see specifically where my code is breaking, I have to use: foreach (DataRow row in data.Rows) { Person newPerson = new Person(); newPerson.Id = row.Field<int>("Id"); newPerson.Name = row

What are good ways to initialize an instance of CBCentralManager, which requires a delegate and is often pointing to the owning class? I could declare the property as an implicitly unwrapped optional but doing so as a general practice seems rather not Swift-like and not very safe. Alternatively, I can declare the property as an optional. But since CBCentralManager's initializers are not declared as failable, it doesn't seem to make sense to declare the instance as such. Implicitly Unwrapped Optional: class MyUnwrappedOptional: NSObject, CBCentralManagerDelegate { var centralManager: