Questions tagged [singleton]
The singleton is a design pattern aiming to ensure that only a single instance of a class can be created and used.
145 questions
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Are there any good and modern approaches, to have variables that feel global (no need to pass them around explicitly), yet are local to an instance?
I'm developing a library in JavaScript (TypeScript, actually) which is split into several modules. It's meant to run both on the web and in non-web environments like Node.js.
The library is meant to ...
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Global Variables State Management
Background:
I am working in a Java environment using Spring Boot, where I often encounter scenarios where global variable state management is critical, especially within singleton services. I have ...
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Are there any benefits to delegation over subclassing/inheritance in the case of a singleton?
Example:
The MacOS API known as Cocoa uses Delegation to specify various behaviors within the app. A Delegate is a separate object that implements a set of methods that are called by an original ...
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Is it considered a code smell to not delete static pointers of a singleton?
I have a singleton that needs to be initialized at the start of the program and it will live on until the end of the program. As is usual in this pattern, a function initializing the singleton creates ...
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Is utilizing a singleton for a cache an antipattern?
I'm currently writing an MVC application and I need a class that can:
A: get, add and remove data(specifically a TreeSet of sorted strings that I want stored in memory, but I doubt the data itself is ...
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Should I use a singleton to represent the application as a whole?
I make sure when designing software/firmware to make heavy use of dependency injection so that different pieces of the application are not directly coupled to one another. This also allows me to (...
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Storing multiple instances on a Singleton?
RefactoringGuru's example Singleton in Python has an _instances dictionary field
class Singleton(type):
_instances = {}
def __call__(cls, *args, **kwargs):
if cls not in cls....
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Using class attributes as globals in Python - is there a catch?
I have found myself in the habit of using code like this.
class glb:
"just for holding globals"
args = None # from argparse
conf = None # from configparser
def main():
......
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Should I design a factory that returns a singleton?
I design a common API for selected printers of different brands in Java. Each printer uses a different underlying SDK with different functions, but any hardware my code runs on will have only one ...
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Would Injecting dependencies in C# as default parameters be a bad practice?
Given the (old) debate over whether Singletons are overused/abused/are worth it - would it be a bad idea to inject the dependencies as default parameters? In this way, we could get rid of defining ...
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How do Singletons differ from Static variables?
Although I do find some (apparently old) posts on the topic on the web, I could not find one here at SE. Thought of raising this here to see if what I read is accurate/is all there is to it.
So ...
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Singleton as Interface for testability via dependancy injection
It can be found in many advices on topic that having Singletons is an anti-pattern. Especially for cases of testability. Can someone please advice/critique on this way (please see code below) of ...
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How should I provide access to "global" objects down to other objects which are contained in a central "application" object
Note This is a bit lengthy to have give a better understanding of the situation and to get some context. You might spot other architectural flaws (it's from an ancient application). I appreciate any ...
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Dependency injection in .NET Core 3.x Worker Services: Why so hard to consume Transient services now?
I have a Repository service that should be Transient. It is used in many applications.
I have a new application that's a Console App, and current guidance suggests implementing my business logic in ...
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Best way to access (grand grand) parent element in gui
I'm creating a multi window gui program, in c++ with Qt Widgets. I do have many custom gui elements, which usually are c++ classes inherited from QWidget or other Qt elements. When foo is the main ...
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