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Should view models be singletons?
No. There’s no reason a ViewModel should be a Singleton. You actually WANT multiple instances (since each is going to vary) rather than a single instance that lives for the run of the application. In MVVM, the lifespan of a given ViewModel would be as long as the user has the window open and finishes their changes.
Is IoC a singleton?
Now, an IoC container will create a singleton object of MyConsoleLogger class and inject it in the constructor of classes wherever we include ILog as a constructor or method parameter throughout the application. Thus, we can register our custom application services with an IoC container in ASP.NET Core application.
Is Android ViewModel a singleton?
Activity scope If no key is provided, the ViewModel will essentially exist as a singleton within the single Activity of the application.
What is an IoC container C#?
IoC Container (a.k.a. DI Container) is a framework for implementing automatic dependency injection. The IoC container creates an object of the specified class and also injects all the dependency objects through a constructor, a property or a method at run time and disposes it at the appropriate time.
Can ViewModel be shared between activities?
You can’t share a ViewModel across Activities. That’s specifically one of the downsides of using multiple activities as per the Single Activity talk. If i want to share the data between activities, are there both using Intet. puExtra and Android jetpack Navigation?
Using SharedViewModel, we can communicate between fragments. If we consider two fragments, both the fragments can access the ViewModel through their activity. Here, one fragment updates the data within the ViewModel which is shared between both the fragments and another fragment observes the changes on that data.
Is it good practice to use a singleton pattern for a ViewModel?
1) Philosophically, is it a good practice to use a SINGLETON PATTERN for this ViewModel, because it’s widespread over all application and it’s used on many places. 2) Isn’t it a problem for ViewModel (and associated ObjectContext) to live for very long time? Thank you! No. There’s no reason a ViewModel should be a Singleton.
What’s the best way to use a singleton?
If you want to take it one step further then you can use an IoC container (DI framework) like Spring (Java) or Unity (.NET). Almost every DI framework will do its own lifetime management and specifically allow you to define a particular service as a single instance (often calling it “singleton”, but that’s only for familiarity).
Why are singletons bad for a design pattern?
The Singleton design pattern is a very specific type of single instance, specifically one that is: Never explicitly freed (implicitly freed on program termination). It is because of this specific design choice that the pattern introduces several potential long-term problems:
Do you need a singleton for a cache?
If you want to get fancy you can call it an “offline cache” or just an offline copy of remote data. A cache does not need to be a singleton. It may need to be a single instance if you want to avoid fetching the same data for multiple cache instances; but that does not mean you actually have to expose everything to everyone.