You can create a List<T> list = new ArrayList<T>(); directly, this can allow all subtypes of T into the list. This is actually little difficult to understand. when you declare it as List<? extends T> list = … It means that it can allow any unknown subtypes of T into the list. But, from that … Read more
The implements keyword treats the A class as an interface, that means C has to implement all the methods defined in A, no matter if they have an implementation or not in A. Also there are no calls to super methods in C. extends behaves more like what you’d expect from the keyword. You have … Read more
For this you have to create one header.xml which will be included in each and every layout for your activities as follows header.xml <RelativeLayout> <TextView android:id=”@+id/txtHeading” …. /> </RelativeLayout> activity_main.xml <RelativeLayout> <!– include your header here –> <include layout=”@layout/header” … /> <!– Rest of your views –> </RelativeLayout> BaseActivity abstract class BaseActivity extends Activity { … Read more
class MyModelAdmin(admin.ModelAdmin): … def changelist_view(self, request, extra_context=None): extra_context = extra_context or {} extra_context[‘some_var’] = ‘This is what I want to show’ return super(MyModelAdmin, self).changelist_view(request, extra_context=extra_context) See: https://docs.djangoproject.com/en/dev/ref/contrib/admin/#django.contrib.admin.ModelAdmin.changelist_view
Short version extends means: The new class is a child. It gets benefits coming with inheritance. It has all the properties and methods of its parent. It can override some of these and implement new ones, but the parent stuff is already included. implements means: The new class can be treated as the same “shape”, … Read more
There is a little known feature in TypeScript that allows you to use Mixins to create re-usable small objects. You can compose these into larger objects using multiple inheritance (multiple inheritance is not allowed for classes, but it is allowed for mixins – which are like interfaces with an associated implenentation). More information on TypeScript … Read more
// How to extend Validator interface adding isArray() method?? You cannot do this in a file that is a module (some guidance here) and your file is a module because you have import expressValidator. Instead create a extendedValidator.d.ts and add the new stuff for TypeScript’s engine: declare module ExpressValidator { export interface Validator { isArray: … Read more
Yes there are differences which may or may not be relevant in your scenario. Perhaps the most significant is the difference in how members with the same property key are handled when present in both types. Consider: interface NumberToStringConverter { convert: (value: number) => string; } interface BidirectionalStringNumberConverter extends NumberToStringConverter { convert: (value: string) => … Read more
I wouldn’t bother trying to merge your Constants class with this class. It isn’t worth the effort. Just create a new class that does what is necessary for ACRA. Like this: public class MyApplication extends Application { @Override public void onCreate() { super.onCreate(); // do the ACRA init here } } Now you need to … Read more
Yes, you can do it. An interface can extend multiple interfaces, as shown here: interface Maininterface extends inter1, inter2, inter3 { // methods } A single class can also implement multiple interfaces. What if two interfaces have a method defining the same name and signature? There is a tricky point: interface A { void test(); … Read more