subclass

问题 What's the difference between UserDict , dict and ABC and which one is recommended? The docs seem to deprecate UserDict ? Also it seems UserDict's update() would use my setitem method whereas dict doesn't? Which methods are really essential to override given I want custom setitem and getitem function? With ABC s I'd have to implement absolutely all methods since it provides no default implementation? I want to make a dict that does two things: intern() all keys and values store some of the

问题 I want to implement a custom list class in Python as a subclass of list . What is the minimal set of methods I need to override from the base list class in order to get full type compatibility for all list operations? This question suggest that at least __getslice__ needs to be overridden. From further research, also __add__ and __mul__ will be required. So I have this code: class CustomList(list): def __getslice__(self,i,j): return CustomList(list.__getslice__(self, i, j)) def __add__(self

问题 I have created a class derived from numpy's ndarray following numpy's documentation, and it looks like (reduce the number of attributes to make it more readable): import numpy as np class Atom3D( np.ndarray ): __array_priority__ = 11.0 def __new__( cls, idnum, coordinates): # Cast numpy to be our class type assert len(coordinates) == 3 obj = np.asarray(coordinates, dtype= np.float64).view(cls) # add the new attribute to the created instance obj._number = int(idnum) # Finally, we must return

问题 Duplicate of C# Accessing a subclass property - see additional solution approaches there. I have an object model where each object has a parent and I would like to access the parent property with the specific type for each object. So e.g. Wheel shall have a parent property of type Car. My guess is that there is an established design pattern for achieving this (in .NET). However, I have not found it so the design I came up with looks like this public class BaseObject<T> where T : BaseObject<T>

问题 I'd like to have a settings view in my app. I want to have things like UILabels, UISwitches etc. (Like in the Settings app.) How can I go about doing that? Can I just replace the detailView with the required view, or is there more to it then that? That may not work because I need to be able to set and get text values too. 回答1: Take a look at this project. If you want to do it yourself, you can e.g. attach your own views to the cell's contentView, or use the accessory view to display your

问题 I am trying to do some polymorphism exercises and I cannot figure out how this kind of polymorphism works. I did not find any deep information about this kind of exercised. I hope you guys could give me some explanation. exercise 1: class Top { public void m( Middle p ) System.out.print("A "); } class Middle extends Top { public void m( Object p ) System.out.print("M "); public void m( Middle p ) System.out.print("L "); } class Bottom extends Middle { public void m( Object p ) System.out

问题 I have a class structure that looks like this: module MyModule class MyOuterClass class MyInnerClass end end end I'm trying to make sure that a variable was correctly instantiated as a MyInnerClass using Rspec. printing the type of the class, it was MyModule::MyOuterClass::MyInnerClass. However, if I try to run the line expect{@instance_of_MyInnerClass}.to be_an_instance_of(MyModule::MyOuterClass::MyInnerClass) I get the error "You must pass an argument rather than a block to use the provided

问题 This is simple I am sure, but I am still very much learning. I have an NSTableView that is connected to an array controller to display coredata objects. The table is uneditable. When a single record is selected, I have a subview set to be made visible that holds the value of the selection. I'm trying to make it so that when I press the + button connected to add: on my array controller, a new entry will be made and the focus will jump to the item description text field in the subview so that a

问题 Imagine a table view controller ExtraRowTableViewController , which always inserts an extra row, after (let's say) the third row. So in this example ... class SomeList:ExtraRowTableViewController override func numberOfSectionsInTableView(tableView: UITableView)->Int { return yourData.count ... say, 50 items } override func tableView (tableView:UITableView, cellForRowAtIndexPath indexPath:NSIndexPath) -> UITableViewCell { return yourData.cell ... for that row number }

问题 Imagine a table view controller ExtraRowTableViewController , which always inserts an extra row, after (let's say) the third row. So in this example ... class SomeList:ExtraRowTableViewController override func numberOfSectionsInTableView(tableView: UITableView)->Int { return yourData.count ... say, 50 items } override func tableView (tableView:UITableView, cellForRowAtIndexPath indexPath:NSIndexPath) -> UITableViewCell { return yourData.cell ... for that row number }