subclass

问题 When in "edit" or "show" this comes up: ActiveRecord::SubclassNotFound in Registries#edit "The single-table inheritance mechanism failed to locate the subclass: 'Plane'. This error is raised because the column 'type' is reserved for storing the class in case of inheritance. Please rename this column if you didn't intend it to be used for storing the inheritance class or overwrite Present.inheritance_column to use another column for that information." 25: </div> 26: 27: <div class="field1"> 28

问题 Hi I'm wondering if there is a simple solution to my problem, I have an ArrayList : ArrayList <Animal> animalList = new ArrayList<Animal>(); /* I add some objects from subclasses of Animal */ animalList.add(new Reptile()); animalList.add(new Bird()); animalList.add(new Amphibian()); They all implement a method move() - The Bird flies when move() is called. I know I can access common methods and properties of the super class by using this public void feed(Integer animalIndex) { Animal aAnimal

问题 I've subclassed DropDownList to add functionality specific to my application: public class MyDropDownList : DropDownList { ... } ... then referenced it in Web.Config , which is where I figure things start to go wrong: <pages theme="Main"> <controls> <add tagPrefix="bob" tagName="MyDropDownList" src="~/Components/MyDropDownList.cs" /> </controls> </pages> my reference to it does not work: <tr><td>Category</td> <td><bob:MyDropDownList runat="server" ID="Category"... /> and my best clue is the

问题 I wanna subclass the PFUser object in swift. I also want to declare my own variables. The Parse documentation on subclassing do not cover PFUser at this point. Parse documentation on subclassing PFObject: class Armor : PFObject, PFSubclassing { class func load() { self.registerSubclass() } class func parseClassName() -> String! { return "Armor" } } 回答1: BridgingHeader.h: #import <Parse/Parse.h> #import <Parse/PFObject+Subclass.h> User.swift: import Foundation class User : PFUser,

问题 In my Java project, I have a vector of various types of Traders. These different types of traders are subclasses of the Trader class. Right now, I have a method that takes a Trader as an argument and stores it 50 or so times in the vector. I am having problems because storing the same object 50 times is just storing 50 references of the same object. I need to store 50 copies of the object. I've researched about implementing Clone, but I don't want the programmers defining a type of Trader to

问题 In my Java project, I have a vector of various types of Traders. These different types of traders are subclasses of the Trader class. Right now, I have a method that takes a Trader as an argument and stores it 50 or so times in the vector. I am having problems because storing the same object 50 times is just storing 50 references of the same object. I need to store 50 copies of the object. I've researched about implementing Clone, but I don't want the programmers defining a type of Trader to

问题 I need to have a few UIViewControllers that look very similar yet have different behaviours, so I thought I'd make a general UIViewController subclass with a xib, then subclass it when I need to, for those different UIViewController's that look alike. I'm trying to achieve the following UIViewController subclass (that has a xib file associated) -> and being able to subclass it as many times as i'd like (without additional xib files for the children) what I've done so far : xib file represents

问题 I need to have a few UIViewControllers that look very similar yet have different behaviours, so I thought I'd make a general UIViewController subclass with a xib, then subclass it when I need to, for those different UIViewController's that look alike. I'm trying to achieve the following UIViewController subclass (that has a xib file associated) -> and being able to subclass it as many times as i'd like (without additional xib files for the children) what I've done so far : xib file represents

问题 I'm trying to create a subclass of SKShapeNode in swift as SKShapeNode(circleOfRadius: radius) but there is no designated init for it. Anyone have any workarounds or info about why? I'm not sure if this is a bug or intentional. I found this video demonstrating a workaround for SKSpriteNode but its not working for me. https://skillsmatter.com/skillscasts/5695-how-to-subclass-a-skspritenode Overall i am trying to make a subclass for an SKShapeNode that i can then subclass from again to have

问题 I'm creating a simple CMS in django, with multiple "modules" (each as a django app). I've set up the following models: class FooObject(models.Model): id = models.SlugField(primary_key=True) name = models.CharField(max_length=255) creator = models.ForeignKey(auth.models.User, editable=False, related_name="createdby") class FooPage(FooObject): content = models.TextField(blank=True, null=True) @models.permalink def get_absolute_url(self): return ('page', (), {'page_id':self.id} class FooSubitem