class-method

问题 In Python, class methods can be inherited. e.g. >>> class A: ... @classmethod ... def main(cls): ... return cls() ... >>> class B(A): pass ... >>> b=B.main() >>> b <__main__.B instance at 0x00A6FA58> How would you do the equivalent in Java? I currently have: public class A{ public void show(){ System.out.println("A"); } public void run(){ show(); } public static void main( String[] arg ) { new A().run(); } } public class B extends A{ @Override public void show(){ System.out.println("B"); } }

问题 I need to maintain a list of methods that will be executed in different orders for testing. We are moving away from C to C++ to use google framework. Is it possible to maintain a list of functions pointers to some of the class methods to be used for execution inside the class, so that they can be used after instantiation ? please refer http://cpp.sh/265y #include <iostream> #include <string> #include <vector> using namespace std; typedef void (*funcType)(); class Sample { public: vector

问题 When sending mail in Rails, usually one would do something like this: UserMailer.password_reset(user).deliver But if we look inside UserMailer we can see this: def password_reset(user) # not self.password_reset # ... end Notice that the method name is not prefixed with self . Looking at it, it seems like you need to instantiate the object first as below. How does Rails do this? UserMailer.new.password_reset(user).deliver 回答1: That's a great question. In the source (https://github.com/rails

问题 I'm using Python 3. I know about the @classmethod decorator. Also, I know that classmethods can be called from instances. class HappyClass(object): @classmethod def say_hello(): print('hello') HappyClass.say_hello() # hello HappyClass().say_hello() # hello However, I don't seem to be able to create class methods dynamically AND let them be called from instances. Let's say I want something like class SadClass(object): def __init__(self, *args, **kwargs): # create a class method say_dynamic

问题 I have difficulties understanding naming conventions of ARC. I have always coded with ARC, and I guess this is the reason. 1. Class methods What name should I choose for the following method? What are the differences, concerning memory management, between theses two names? This name: + (MyObject *)newObjectFrom:(MyObject *)anObject withOptions:(NSDictionary*)options { MyObject * newObject = [anObject copy] ; [newObject modifyWith:options] ; return newObject ; } or this name ? + (MyObject *

问题 In my code file MyItemVC.swift I have defined the following class and method: class MyItemVC: UIViewController, UITextViewDelegate { var timer = NSTimer() func cycleTimer(toggleOn: Bool) { if toggleOn == true { // Timer calls the replaceItem method every 3 seconds timer = NSTimer.scheduledTimerWithTimeInterval(3, target: self, selector: Selector("replaceItem"), userInfo: nil, repeats: true) } else { timer.invalidate() // stop the timer } } } Elsewhere in this class, I call cycleTimer(true) to

问题 Newbie here, having a hard time understanding Class methods and why I cannot get an attribute to show up correctly in the instance. class Animal attr_accessor :noise, :color, :legs, :arms def self.create_with_attributes(noise, color) animal = self.new(noise) @noise = noise @color = color return animal end def initialize(noise, legs=4, arms=0) @noise = noise @legs = legs @arms = arms puts "----A new animal has been instantiated.----" end end animal1 = Animal.new("Moo!", 4, 0) puts animal1

问题 I have a class method that gets called by a view controller. I want the view controller to be aware of when the class method has finished its tasks (it has threads on it). I think I should use delegation, but I need an id delegate , and I can't call it by self.delegate , because there is no self in a class method. How should I do this? Thanks! 回答1: You can store a delegate at class-level (even separate from an object-level delegate), but it sounds a bit fishy to me. Here's how you'd do it: In

问题 I want to assign a static method to a class variable in Python, and below is what my code looks like. class Klass: classVariable = None @staticmethod def method(): print "method called" Klass.classVariable = Klass.method Klass.method() Klass.classVariable() This gave me an error at the last line, TypeError: unbound method method() must be called with Klass instance as first argument (got nothing instead). But when I change the static method to class method it works. Can anyone give me any

问题 Can you create a decorator inside a class that will see the classes methods and variables? The decorator here doesnt see: self.longcondition() class Foo: def __init__(self, name): self.name = name # decorator that will see the self.longcondition ??? class canRun(object): def __init__(self, f): self.f = f def __call__(self, *args): if self.longcondition(): # <-------- ??? self.f(*args) # this is supposed to be a very long condition :) def longcondition(self): return isinstance(self.name, str)