subclass

I want to write a function that works on any Scala type with a total ordering (i.e. I can use '<' on it). What's the syntax for that? The best I've come up with is def lessThan[T <: Ordered[T]](x: T, Y: T) = x < y That doesn't work, though, when I try using it from the REPL: scala> lessThan(1, 2) <console>:8: error: inferred type arguments [Int] do not conform to method lessThan's type parameter bounds [T <: Ordered[T]] lessThan(1, 2) ^ scala> import runtime._ import runtime._ scala> lessThan(new RichInt(1), new RichInt(2)) <console>:8: error: inferred type arguments [scala.runtime.RichInt] do

I'm trying to create class which is a subclass of SKSpriteNode and I want to add other properties and functions to it. But in the first step I faced an error. Here's my code: import SpriteKit class Ball: SKSpriteNode { init() { super.init(imageNamed: "ball") } } It's not a compile error, It's run-time error. It says: Thread 1: EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0) and fatal error: use of unimplemented initializer 'init(texture:)' for class Project.Ball . How can I fix it? Mike S You have to call the designated initializer for SKSpriteNode . I'm actually surprised you didn't

I have a class A and a class B that inherits class A and extends it with some more fields. Having an object a of type A , how can I create an object b of type B that contains all data that object a contained? I have tried a.MemberwiseClone() but that only gives me another type A object. And I cannot cast A into B since the inheritance relationship only allows the opposite cast. What is the right way to do this? There is no means of doing this automatically built into the language... One option is to add a constructor to class B that takes a class A as an argument. Then you could do: B newB =

(I am using python 2.7) The python documentation indicates that you can pass a mapping to the dict builtin and it will copy that mapping into the new dict: http://docs.python.org/library/stdtypes.html#mapping-types-dict I have a class that implements the Mapping ABC, but it fails: import collections class Mapping(object): def __init__(self, dict={}): self.dict=dict def __iter__(self): return iter(self.dict) def __iter__(self): return iter(self.dict) def __len__(self): return len(self.dict) def __contains__(self, value): return value in self.dict def __getitem__(self, name): return self.dict

I would like to ask what is the good practice on using anonymous classes vs. named inner classes? I am writing an Android application, which includes many UI elements (buttons, text fields, etc). For many of them I need some kind of listeners, so in onCreate of the application I have bunch of quite small anonymous classes like: someButton.setOnClickListener( new View.OnClickListener() { public void onClick(View v) { // do something... } } ); Each of of such anonymous class is 5 - 20 lines big - small enough and fits good for recommendations from Java™ in a Nutshell book: In general, you should

In Objective C, if you are subclassing something, and are planning to override a method on the superclass, should you re-declare the superclass method in your subclass @interface? For example, if you are subclassing UIViewController (e.g. MyViewController), and you are planning to override "viewDidLoad" should you include that method in your MyViewController @interface declaration, or just implement it in MyViewController.m? In examples I've come across, I've seen it done both ways (re-declaring the method in your subclass interface, or not re-declaring the method). There may not be any

I have created a class that extends Array. I want to execute arbitrary code before calling the inherited push function. class newArray extends Array{ //execute any logic require before pushing value onto array this.push(value) } Udesh The solution I found was to create a new function in the subclass that has the same name as the inherited function. In this case push. Then inside the overriding function the inherited function is called via the super keyword. class newArray extends Array{ push(value) { //execute any logic require before pushing value onto array console.log(`pushed ${value} on to