subclass

问题 By default all code-behind classes inherit from PhoneApplicationPage . I would like to make a subclass of PhoneApplicationPage and use it as basis for my code-behind class, like so: namespace Test { public partial class HistoryRemoverPage : PhoneApplicationPage { protected override void OnNavigatedTo (NavigationEventArgs e) { if (e.NavigationMode == NavigationMode.New) NavigationService.RemoveBackEntry(); } } } namespace Test { public partial class MainPage : HistoryRemoverPage { public

问题 Ok... in Objective C you can new up a subclass from a static method in the base class with 'new this()' because in a static method, 'this' refers to the class, not the instance. That was a pretty damn cool find when I first found it and I've used it often. However, in C# that doesn't work. Damn! So... anyone know how I can 'new' up a subclass from within a static base class method? Something like this... public class MyBaseClass{ string name; public static Object GimmeOne(string name){ //

问题 I want to subclass dict in python such that all the dictionaries of the sub-class are immutable. I don't understand how does __hash__ affects the immutability, since in my understanding it just signifies the equality or non-equality of objects ! So, can __hash__ be used to implement immutability ? How ? Update : Objective is that common response from an API is available as a dict, which has to be shared as a global variable. So, that needs to be intact no matter what ? 回答1: I found an

问题 In the Chapter 7.3.5 "Inheritance and Instance Variables" of the book "the ruby programing language" says : Because instance variables have nothing to do with inheritance, it follows that an instance variable used by a subclass cannot “shadow” an instance variable in the superclass. If a subclass uses an instance variable with the same name as a variable used by one of its ancestors, it will overwrite the value of its >ancestor’s variable. This can be done intentionally, to alter the behavior

问题 So I have a class, character(), and a subclass, npc(character). They look like this: class character(): def __init__(self,name,desc): self.name = name self.desc = desc self.attr = "" #large list of attributes not defined by parameters and class npc(character): def __init__(self,greetings,topics): self.greetings = greetings self.topics = topics character.__init__(self) self.pockets = [] #more attributes specific to the npc subclass not defined by parameters however, when I call an attribute

问题 What is the command line syntax for generating a subclass model or scaffold in Rails? rails g model Mysubclass my_field:string .... How do I specify the parent class? 回答1: You can use "--parent=ParentClass". Example: 1) Create a parent class "User". rails g scaffold User login:string 2) Create a child class "Teacher". rails g scaffold Teacher url:string --parent=User But remember: you still need to create migrations(adding columns in datatables) and change views(adding fields in forms). 回答2:

问题 Is it possible to get all subclasses of given class in php? 回答1: function getSubclassesOf($parent) { $result = array(); foreach (get_declared_classes() as $class) { if (is_subclass_of($class, $parent)) $result[] = $class; } return $result; } Coincidentally, this implementation is exactly the one given in the question linked to by Vadim. 来源： https://stackoverflow.com/questions/3470008/how-to-obtain-all-subclasses-of-a-class-in-php

问题 class testWidget(QtGui.QWidget): def __init__(self, parent=None): super(testWidget, self).__init__(parent) self.parent = parent self.something() def something(self): self.parent.callme() # self.parent?.... nice? class testClass(): def __init__(self): self.widget = testWidget(parent=self) test = testClass() What is the cleanest way of dealing with a parent class in python(pyqt)? Is there a nicer way than calling self.parent directly? 回答1: If you want to call a method of this widget's parent

问题 I've been trying to add a gradient to the UITabBar in my app. After a few failed attempts I followed the steps from this question and the. gradient now works, but the UITabBarItems are invisible (although they all work). How can I make sure that both the gradient and the UIITabBarItems are visible? class GradientTabBarController: UITabBarController { let layerGradient = CAGradientLayer() override func viewDidLoad() { super.viewDidLoad() print("custom tabbar loaded") layerGradient.colors =

问题 I'm trying to subclass UIImageView to add some custom functionality in it. I started trying to do the basics, just init an object with a given image and display it on the screen. Using UIImageView everything works fine, but if i change my object from UIImageView to my custom class, no image is displayed. Here's what i've done so far: //Imager.h #import <UIKit/UIKit.h> @interface Imager : UIImageView { } -(id) init; -(void) retrieveImageFromUrl: (NSString *)the_URL; @end //Imager.m #import