inheritance

问题 I'm have a parent class, and I would like to "force" everyone that will inherit from it to implement some specific class attributes. I don't have this problem with methods, since I have created a dummy method that raises NotImplementedError , which makes it very clear. As for class attributes- I do not want to create them in the parent class and set them to None since that doesn't force the developer to implement them in the child class. A little code to demonstrate the current situation:

问题 I have a situation where in C# I consume data via an OData API. Actually, there are two different OData endpoints (two different models), where one is a superset of the other. I have created two different C# projects (A and B) which contain code to interact with the two API's. The code is automatically generated using Unchase OData Connected Service extension. As a result, project A and project B both contain a class ODataService , which is the main type to interact with. Depending on whether

问题 I have a situation where in C# I consume data via an OData API. Actually, there are two different OData endpoints (two different models), where one is a superset of the other. I have created two different C# projects (A and B) which contain code to interact with the two API's. The code is automatically generated using Unchase OData Connected Service extension. As a result, project A and project B both contain a class ODataService , which is the main type to interact with. Depending on whether

问题 I have an abstract model and a few other classes that inherit from it. # models.py class Parameter(models.Model): data = integer = models.IntegerField(blank=True, null=True) class Meta: abstract = True class Temperature(Parameter): received_timestamp = models.DateTimeField(default=datetime.now, blank=True) class Ph(Parameter): received_timestamp = models.DateTimeField(default=datetime.now, blank=True) although my Parameter class is abstract, I get models.E006 error in python manage.py

问题 class LinkedNode<T> { var value: T var next: Self? required init(_ value: T) { self.value = value } } class DoublyNode<T>: LinkedNode<T> { weak var previous: DoublyNode? override var next: Self? { didSet { next.previous = self } } } I wish it compiles like this. But it doesn't. Stored property cannot have covariant 'Self' type I have to rewrite the code to make it compile and work: class LinkedNode<T> { var value: T var next: LinkedNode? required init(_ value: T) { self.value = value } }

问题 class LinkedNode<T> { var value: T var next: Self? required init(_ value: T) { self.value = value } } class DoublyNode<T>: LinkedNode<T> { weak var previous: DoublyNode? override var next: Self? { didSet { next.previous = self } } } I wish it compiles like this. But it doesn't. Stored property cannot have covariant 'Self' type I have to rewrite the code to make it compile and work: class LinkedNode<T> { var value: T var next: LinkedNode? required init(_ value: T) { self.value = value } }

问题 class LinkedNode<T> { var value: T var next: Self? required init(_ value: T) { self.value = value } } class DoublyNode<T>: LinkedNode<T> { weak var previous: DoublyNode? override var next: Self? { didSet { next.previous = self } } } I wish it compiles like this. But it doesn't. Stored property cannot have covariant 'Self' type I have to rewrite the code to make it compile and work: class LinkedNode<T> { var value: T var next: LinkedNode? required init(_ value: T) { self.value = value } }

问题 class LinkedNode<T> { var value: T var next: Self? required init(_ value: T) { self.value = value } } class DoublyNode<T>: LinkedNode<T> { weak var previous: DoublyNode? override var next: Self? { didSet { next.previous = self } } } I wish it compiles like this. But it doesn't. Stored property cannot have covariant 'Self' type I have to rewrite the code to make it compile and work: class LinkedNode<T> { var value: T var next: LinkedNode? required init(_ value: T) { self.value = value } }

问题 I have created a 'template' project A which has 10 controllers ( partial class ). All these controllers are packed in a nuget package and are consumed by projects B, C & D. The nuget generates the controllers in the folder controllers/_core so they are nicely stored separately. The nuget package does not have a reference to the dll of project A. Now to get down to the problem; It could be that one of the controllers that are generated need to be modified. By adding a second partial we could

问题 I have created a 'template' project A which has 10 controllers ( partial class ). All these controllers are packed in a nuget package and are consumed by projects B, C & D. The nuget generates the controllers in the folder controllers/_core so they are nicely stored separately. The nuget package does not have a reference to the dll of project A. Now to get down to the problem; It could be that one of the controllers that are generated need to be modified. By adding a second partial we could