ThomasM, We had similar ideas about encapsulating behavior inside a custom view (say, a slider with companion labels for min/max/current values, with value-changed events also handled by the control internally). In our current best-practice, we would design the ShareView in Interface Builder (ShareView.xib), as described by Eimantas in his answer. We then embed the ShareView … Read more
What is happening is that each subview inside the TableViewCell will receive the setSelected and setHighlighted methods. The setSelected method will remove background colors but if you set it for the selected state it will be corrected. For example if those are UILabels added as subviews in your customized cell, then you can add this … Read more
The abstract base classes provided in the collections module, particularly MutableSequence, can be useful when implementing list-like classes. These are available in Python 2.6 and later. With ABCs you can implement the “core” functionality of your class and it will provide the methods which logically depend on what you’ve defined. For example, implementing __getitem__ in … Read more
Overwriting __new__() works if you want to modify the string on construction: class caps(str): def __new__(cls, content): return str.__new__(cls, content.upper()) But if you just want to add new methods, you don’t even have to touch the constructor: class text(str): def duplicate(self): return text(self + self) Note that the inherited methods, like for example upper() will … Read more
On the example you give, you first try to retrieve a non-existing value on the list, as you do dl[2][‘a’], Python first retrieve the third (index 2) element on the list, then proceed to get the element named ‘a’ on that object – therefore you have to implement your automatic extending behavior to the __getitem__ … Read more
Because every instance of the subclass still needs to be a valid instance of the base class (see Liskov substitution principle). If the subclass suddenly has lost one property of the base class (namely a public method for example) then it would no longer be a valid substitute for the base class.
It seems Swashbuckle doesn’t implement polymorphism correctly and I understand the point of view of the author about subclasses as parameters (if an action expects an Animal class and behaves differently if you call it with a dog object or a cat object, then you should have 2 different actions…) but as return types I … Read more
There is now an official guide on how to subclass Pandas data structures, which includes DataFrame as well as Series. The guide is available here: https://pandas.pydata.org/pandas-docs/stable/development/extending.html#extending-subclassing-pandas The guide mentions this subclassed DataFrame from the Geopandas project as a good example: https://github.com/geopandas/geopandas/blob/master/geopandas/geodataframe.py As in HYRY’s answer, it seems there are two things you’re trying to accomplish: … Read more
Member variables cannot be overridden like methods. The number variables in your classes Beta and Gama are hiding (not overriding) the member variable number of the superclass. By casting you can access the hidden member in the superclass.
The problem is that you’re making a promise that the compiler can’t prove you’ll keep. So you created this promise: Calling copy() will return its own type, fully initialized. But then you implemented copy() this way: func copy() -> Self { return C() } Now I’m a subclass that doesn’t override copy(). And I return … Read more