abstract-class

Flutter: inherit from abstract stateless widget

五迷三道 提交于 2021-02-19 03:19:44
问题 I have a class that has to take a custom widget. This one can have two different implementations, so I would like to have an abstract class as interface and create two other classes those extend the abstract one. So, I have: abstract class ICustomWidget extends StatelessWidget{} class A extends ICustomWidget{ @override Widget build(BuildContext context) => //Implementation } class B extends ICustomWidget { @override Widget build(BuildContext context) => //Implementation } I want to ask if

Flutter: inherit from abstract stateless widget

风格不统一 提交于 2021-02-19 03:19:29
问题 I have a class that has to take a custom widget. This one can have two different implementations, so I would like to have an abstract class as interface and create two other classes those extend the abstract one. So, I have: abstract class ICustomWidget extends StatelessWidget{} class A extends ICustomWidget{ @override Widget build(BuildContext context) => //Implementation } class B extends ICustomWidget { @override Widget build(BuildContext context) => //Implementation } I want to ask if

Flutter: inherit from abstract stateless widget

大城市里の小女人 提交于 2021-02-19 03:19:00
问题 I have a class that has to take a custom widget. This one can have two different implementations, so I would like to have an abstract class as interface and create two other classes those extend the abstract one. So, I have: abstract class ICustomWidget extends StatelessWidget{} class A extends ICustomWidget{ @override Widget build(BuildContext context) => //Implementation } class B extends ICustomWidget { @override Widget build(BuildContext context) => //Implementation } I want to ask if

Flutter: inherit from abstract stateless widget

末鹿安然 提交于 2021-02-19 03:18:43
问题 I have a class that has to take a custom widget. This one can have two different implementations, so I would like to have an abstract class as interface and create two other classes those extend the abstract one. So, I have: abstract class ICustomWidget extends StatelessWidget{} class A extends ICustomWidget{ @override Widget build(BuildContext context) => //Implementation } class B extends ICustomWidget { @override Widget build(BuildContext context) => //Implementation } I want to ask if

Abstract class or interface. Which way is correct?

孤者浪人 提交于 2021-02-17 22:17:38
问题 There are two way for choosing between abstract class or interface. Microsoft solution and Oracle solution: Microsoft, design guideline: Do use abstract (MustInherit in Visual Basic) classes instead of interfaces to decouple the contract from implementations. http://msdn.microsoft.com/en-us/library/ms229013.aspx Oracle, The Java Tutorials: If an abstract class contains only abstract method declarations, it should be declared as an interface instead. http://docs.oracle.com/javase/tutorial/java

Java how does graphics abstract drawline method really works?

旧时模样 提交于 2021-02-17 02:00:35
问题 I read source code of Java Graphics abstract class, I am curious how does this abstract void drawline method draws lines in JComponent's paint(Graphics g) and paintComponent(Graphics g). I know that abstract methods have no method body. I couldn't find any relevant examples with Google. If possible, can you provide me a link to source code of this method. 回答1: Mad Programmer is right, all of java's graphics and graphics2d methods is directed with native codes. If you're curious about these

Prohibit addition of new methods to a Python child class

给你一囗甜甜゛ 提交于 2021-02-16 18:06:53
问题 I have two classes that are supposed to implement the same test cases for two independent libraries (let's call them LibA and LibB ). So far I define the test methods to be implemented in an abstract base class which ensures that both test classes implement all desired tests: from abc import ABC, abstractmethod class MyTests(ABC): @abstractmethod def test_foo(self): pass class TestsA(MyTests): def test_foo(self): pass class TestsB(MyTests): def test_foo(self): pass This works as expected, but

why abstract class instantiation isn't runtime error in dart?

为君一笑 提交于 2021-02-09 05:50:09
问题 In many languages if you try to instantiate abstract class you get compile time error. In Dart however, you get warning while compiling and a runtime exception AbstractClassInstantiationError . Why is that? Can someone provide an example, where it's reasonable to compile such code? 回答1: Dart tries to allow you to run your program while you are developing it. That is why many things that are compile time errors in other languages are compile-time warnings and runtime errors in Dart. This

Why does null check fail even though object is explicitly initialized as null

强颜欢笑 提交于 2021-02-08 10:14:53
问题 I have created a custom abstract class, which in turn of course derived classes were also created. public abstract class AbstractBaseClass ... public class ChildClass1 : AbstractBaseClass ... Now, whenever I declare for example AbstractBaseClass baseClass = null , and wherever null checks follow after this initialization, it always fails. if (baseClass == null) { // this block is never reached - condition always evaluates to false // let's say AbstractBaseClass baseClass = null is at line 10

Can a django model have two abstract classes?

梦想的初衷 提交于 2021-02-07 21:53:00
问题 I have this models: class BillHeader(models.Model): billno = models.IntegerField(primary_key=True, blank=True) class BillData(models.Model): price = models.DecimalField(_('Price'), max_digits=12, decimal_places=2) amount = models.DecimalField(_('Amount'), max_digits=6, decimal_places=2) [... rest of the model ...] class Meta: abstract = True class BillFooter(models.Model): total = models.DecimalField(_('Total'), max_digits=12, decimal_places=2) [... rest of the model ...] class Meta: abstract