singleton

Ruby access magic

由 前提是你 提交于 2019-12-08 06:38:20
问题 Assume, I have the following class: class MyClass attr_accessor :vars def initialize @vars = [] end def add_var var @vars << var end end I want to access inners vars like this: x = MyClass.new('root') x.add_var 'test' x.add_var 'something' x.add_var Myclass.new('google') x.google.add_var 'nice' puts x.test puts x.something puts x.google.nice Generally speaking, is it possible? What/where should I dig for? 回答1: It's part of the standard Ruby library, and it's called OpenStruct: #!/usr/bin

@Singleton @Startup fully Asynchronous?

由 ε祈祈猫儿з 提交于 2019-12-08 06:24:34
问题 I am using the @Singleton and @Startup annotations together to create a long running process. By using these annotation can I safely assume that my process will be a single thread running fully asynchronously? 回答1: You can use these annotations just at the class-level, so I'm not sure what 'process' do you refer to (@PostConstruct method?) I don't remember any part of the EJB 3.1 specification which talks about the required asynchronous singleton initialization. 4.8.1 Singleton Initialization

Thread safety of method calls on “shared” static constant property

由 大城市里の小女人 提交于 2019-12-08 06:22:18
问题 I have a Swift class which uses a traditional Cocoa singleton pattern: one static shared constant and a private init that is only called once for that shared constant. It's like this: public class Foo { public static let shared = Foo() private init() { /* ... */ } public func bar() { /* ... */ } public func baz() { /* ... */ } } // Meanwhile, in multiple places upon multiple threads: Foo.shared.bar() Foo.shared.baz() If I have a dozen threads calling functions on that constant, does it pause

What is the better way of publishing global constants in Java?

由 ╄→尐↘猪︶ㄣ 提交于 2019-12-08 06:02:25
问题 Which one of these ways of publishing global constants is better? THANKS!!! Method 1: final class with public static final fields public final class CNST{ private CNST(){} public static final String C1; public static final String C2; static{ C1="STRING1"; C2="STRING2"; } } //so I could call C1, C2 like: //...some code... //System.out.println(CNST.C1); //System.out.println(CNST.C2); Method 2: singleton with enum public enum CNST{ INST; public final String C1; public final String C2; CNST{ C1=

Using Java Singleton instance in a multi threaded environment

由 ≯℡__Kan透↙ 提交于 2019-12-08 05:50:42
问题 My application wants to communicate with a REST server. At first, we need to authenticate and in response to that, we will receive a client token . This token is valid for 30 minutes and for the rest of the communication this client token needs to be present as a header. I am planning to implement a Singleton Class that handles the REST communication. Reson for not following an ENUM approach (as mentioned in many other threads) is because of the requirement to make a rest call and populate

Singletons: Pros,Cons, Design Concerns [closed]

由 不问归期 提交于 2019-12-08 05:43:24
As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by facts, references, or expertise, but this question will likely solicit debate, arguments, polling, or extended discussion. If you feel that this question can be improved and possibly reopened, visit the help center for guidance. Closed 8 years ago . I admit it. I am using singletons. I know what you may all say, and frankly, seeing all these answers on the Internet, saying about the bad aspects of singletons, and advising against them really made me question my programming practices

Should I use a singleton?

由 做~自己de王妃 提交于 2019-12-08 05:25:30
This is a semi-related question to question to the following question I just raised: Utility classes.. Good or Bad? After determining that a class is to act as a cache for Url parsing rules stored in an XML file, I have considered that a singleton would solve my problem, but introduce global state (although it is only traveling in one direction XML -> parser), and static dependencies. The design consideration that led me to consider a singleton was: (note that this is a web application that uses a module to catch and parse ALL requests using the same parser) I need to cache the url parsing

Should I use a singleton?

由 时间秒杀一切 提交于 2019-12-08 05:16:02
问题 This is a semi-related question to question to the following question I just raised: Utility classes.. Good or Bad? After determining that a class is to act as a cache for Url parsing rules stored in an XML file, I have considered that a singleton would solve my problem, but introduce global state (although it is only traveling in one direction XML -> parser), and static dependencies. The design consideration that led me to consider a singleton was: (note that this is a web application that

Singleton in C#

由 此生再无相见时 提交于 2019-12-08 05:06:37
问题 I would like to collect more variants for create singleton class. Could you please provide to me the best creation way in C# by your opinion. Thanks. public sealed class Singleton { Singleton _instance = null; public Singleton Instance { get { if(_instance == null) _instance = new Singleton(); return _instance; } } // Default private constructor so only we can instanctiate private Singleton() { } // Default private static constructor private static Singleton() { } } 回答1: I have an entire

Asynchronous task queue processing of in-memory data stucture in Django

由 ＊爱你＆永不变心＊ 提交于 2019-12-08 05:00:43
问题 I have a singleton in-memory data-structure inside my Django project (some kind of kd-tree that needs to get accessed all across the project). For those that don't know Django, I believe the same issue would appear with a regular Python code. I know it's evil (Singleton), and I'm looking for better ways to implement that, but my question here is related to another topic: I am instantiating the singleton inside my code by calling Singleton.instance() and it gives me the object correctly, it
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