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问题 I have an ActiveRecord class called 'DynObject' which can be used for inheritance.. On initialization I dynamically create some Classes that inherit from it: classes_config = { foo: 'foo', bar: 'bar' } classes_config.each do |name,options| klass = Class.new( DynObject ) do end self.klasses[name] = const_set( "#{name.camelize}DynObject", klass ) end This is all good, these classes are created just fine.. But when ActiveRecord tries to load created records the STI mechanism failes..

问题 I want a static inner class that can't be instantiated even by the external class. Right now I just have a documentation that says "Please don't instantiate this object". Can I give a better signal? 回答1: I want a static inner class that can't be instantiated even by the external class. I assume that "external class" really means the enclosing class. If you don't want to restrict the enclosing class, then making the only constructor of the inner class private will have the desired effect. If

问题 var search_name = location.search; if (search_name.search("cate_no=24") > 0) { $(".cate_new a").addClass("active"); } }); If current document url is http://abc.com/list.html?cate_no=24, I want to add class "active" into li a. I searched and found these js code, but it doesn't work. Is it wrong? 回答1: It's incorrect. search() returns the offset position of a match if a match is found, and -1 if a match isn't found. As you are checking for whether cate_no=24 contains cate_no=24 , it will return

问题 class A{ public: B b; }; class B{ public: A a; }; I can't write in A class "B b" because class B defined below. Is any way to make it work? thanks 回答1: This is not possible. You need to use a pointer or a reference in one of the classes. class B; // forward declare class B class A { public: B * b; }; class B { public: A a; }; As to why it isn't possible: A contains a B contains an A contains a B ... There's no end to the recursion. If you're used to languages (such as e.g. java) where all

问题 I have a class object which i want to access in all the files in c# project Ofcourse i dont want 'static' qualifiers because i want to serialize this object finally. 回答1: Make the class public . You should then be able to create instances wherever you need. If you want a single instance to be accessible throughout your entire project, I would suggest checking out the Singleton pattern. 回答2: If you want to you to use only one instance of this class - use one of the most popular pattern

问题 I am writing configuration program for my own Linux distribution. The configuration is divided into sections: general, networking, session, etc. - which groups similar options. E.g. in section general there are computer name, description, workgroup, language options. I think every section should be presented by the class, and each option should have corresponding property (getter and maybe setter). Moreover it would be nice for generalization if there was function to test if given option is

问题 I don't understand this warning: found raw type: javax.swing.DefaultListModel missing type arguements for generic class javax.swing.DefaultListModel Netbeans seems to indicate that more information can be found from alt-enter but nothing comes up. The type should be ? code: package net.bounceme.dur.nntp.swing; import java.util.logging.Logger; import javax.swing.DefaultListModel; public class MessagesListModel extends DefaultListModel { private static final long serialVersionUID = 1L; private

问题 Why does i remain the same even after a new instance of the class is created? class Test(object): i = 0 def add(self): Test.i += 1 Running this code t = Test() print t.i t.add() t2 = Test() print t2.i print t.i Gives 0 1 1 Why didn't both t.i and t2.i equal 0? Shouldn't they have equaled 0 because the line t2 = Test() would have reset i to 0? 回答1: i is a class variable, not an instance variable. It is bound to the class itself (which is why you can write Test.i , even if no instances of Test

问题 I'm building a class to save data to the Database, but I'm without ideas on how to deal with this... I have my project folders like this: +Lib +Models +Uddt -person.php -uris.php Main_class.php Example_usage.php The folder "Models" have the uris.php file that have methods to add and retrive information from the database tables. The folder "Models\Uddt" have the User Defined Data Types that I have defined, for example, the person.php looks like this: class Person { static $id_category = '2';

问题 How does adding master = Tk() into the __init__ of a subclass of tkinter.Frame produce two windows ( app and app2 ) when only app.mainloop() is called? from tkinter import Frame,Button,Tk class Application(Frame): def say_hi(self): print('Hello world?!') def close(self): self.master.destroy() def createWidgets(self): self.quit_b = Button(self, width=12, text='Quit', bg='tan', command=self.close) self.quit_b.grid(row=0, column=0, padx=8, pady=8) self.hello_b = Button(self, width=12, text=