class-instance-variables

问题 Sorry for the basic question but I'm learning, new to programming. I am trying to call a method that is in another class but I'm unable to without passing in the required values for the constructor of Cypher class. Do i really need a new instance of Cypher class each time i use a method in the Menu class and want to call a method of the Cypher class or how do I rewrite to avoid below. public class Runner { private static Cypher c; public static void main(String[] args) { Menu m = new Menu();

问题 class Something @@variable = 'Class variable' def give_me @@variable end end class OtherThing @variable = 'Instance variable with an interface' class << self attr_accessor :variable end def give_me self.class.variable end end p Something.new.give_me p OtherThing.new.give_me What I want to know is, which one should I use? Which are the benefits and cons of each? Class variables are: Private unless you make an interface Shared between inheritances Shorter to write Class-instance variables are:

问题 class Something @@variable = 'Class variable' def give_me @@variable end end class OtherThing @variable = 'Instance variable with an interface' class << self attr_accessor :variable end def give_me self.class.variable end end p Something.new.give_me p OtherThing.new.give_me What I want to know is, which one should I use? Which are the benefits and cons of each? Class variables are: Private unless you make an interface Shared between inheritances Shorter to write Class-instance variables are:

问题 If I have a class with an attr_accessor , it defaults to creating an instance variable along with the corresponding getters and setters. But instead of creating an instance variable, is there a way to get it to create a class variable or a class instance variable instead? 回答1: Like this: class TYourClass class << self attr_accessor :class_instance_variable end end You can look at this as opening the metaclass of the class (of which the class itself is an instance) and adding an attribute to

问题 my idea is to create a community wiki for people that come from a java background because reading a lot of explanations, I couldn't comprehend anything until I actually tried a couple of things and the pieces of the puzzle started to find their places. But I first need to make sure I'm getting it right. Coming from such background it was very confusing for me to find out that @variable may mean 2 very different things. Here is an example: class Test @ins = "gah" def self.ins puts @ins end def

问题 Can anyone tell me about the difference between class variables and class instance variables? 回答1: A class variable ( @@ ) is shared among the class and all of its descendants. A class instance variable ( @ ) is not shared by the class's descendants. Class variable ( @@ ) Let's have a class Foo with a class variable @@i , and accessors for reading and writing @@i : class Foo @@i = 1 def self.i @@i end def self.i=(value) @@i = value end end And a derived class: class Bar < Foo end We see that

问题 Can anyone tell me about the difference between class variables and class instance variables? 回答1: A class variable ( @@ ) is shared among the class and all of its descendants. A class instance variable ( @ ) is not shared by the class's descendants. Class variable ( @@ ) Let's have a class Foo with a class variable @@i , and accessors for reading and writing @@i : class Foo @@i = 1 def self.i @@i end def self.i=(value) @@i = value end end And a derived class: class Bar < Foo end We see that

问题 Here is the link to my first question: Creating class instance from dictionary? So I am trying to create class instance from dictionary which holds keys that class has not. For example: class MyClass(object): def __init__(self, value1, value2): self.attr1 = value1 self.attr2 = value2 dict = {'attr1': 'value1', 'attr2': 'value2', 'redundant_key': 'value3'} Before creating class instance I have to delete this redundant_key from dict dict.pop('redundant_key', None) new_instance = MyClass(**dict)

问题 Disclaimer : This is for a semester project that I am currently working on. My question is regarding an implementation level detail and is not part of the grading scheme. I am only writing this code as a way to test the theory that I am proposing for the paper that I will write. Also, I have considered the answers for this question with little luck, so please do not consider this as a duplicate of that question The Problem : I have a graph (G=(V,E)). At some point in my algorithm, I need to

问题 I have created some Python classes to use as multivariate data structures, which are then used for various tasks. In some instances, I like to populate the classes with various value sets. The default parameter filename "ho2.defaults" would look something like this: name = 'ho2' mass_option = 'h1o16' permutation = 'odd' parity = 'odd' j_total = 10 lr = 40 br = 60 jmax = 60 mass_lr = 14578.471659 mass_br = 1781.041591 length_lr = ( 1.0, 11.0, 2.65 ) length_br = ( 0.0, 11.0, 2.46 ) use_spline =