abstract-methods

问题 I was reading official python documentation. In the mentioned link, the second line states that: Using this decorator requires that the class’s metaclass is ABCMeta or is derived from it. But, I was successfully able to define the below given class. from abc import abstractmethod class A(object): def __init__(self): self.a = 5 @abstractmethod def f(self): return self.a a = A() a.f() So, the code above worked fine. And also, I was able to create a subclass class B(A): def __init__(self): super

问题 I was reading official python documentation. In the mentioned link, the second line states that: Using this decorator requires that the class’s metaclass is ABCMeta or is derived from it. But, I was successfully able to define the below given class. from abc import abstractmethod class A(object): def __init__(self): self.a = 5 @abstractmethod def f(self): return self.a a = A() a.f() So, the code above worked fine. And also, I was able to create a subclass class B(A): def __init__(self): super

问题 I understand that in abstract classes methods be both abstract, or not. But why can I not create an abstract method in a "normal", non-abstract class? Thanks in advance for any explanation! 回答1: Abstract method basically says, that there is no implementation of the method and it needs to be implemented in a subclass . However if you had an abstract method in a non-abstract class, you could instantiate the class and get an object, that would have an unimplemented method, which you would be

问题 I understand that in abstract classes methods be both abstract, or not. But why can I not create an abstract method in a "normal", non-abstract class? Thanks in advance for any explanation! 回答1: Abstract method basically says, that there is no implementation of the method and it needs to be implemented in a subclass . However if you had an abstract method in a non-abstract class, you could instantiate the class and get an object, that would have an unimplemented method, which you would be

问题 This question already has an answer here : What should I put in the body of an abstract method in Python (1 answer) Closed 2 years ago . I have an abstract class, Model , with a few abstract methods, what should I put in the body of the methods? A return class Model(metaclass=ABCMeta): @abstractmethod def foo(self): return A pass class Model(metaclass=ABCMeta): @abstractmethod def foo(self): pass Raising a descriptive error class Model(metaclass=ABCMeta): @abstractmethod def foo(self): raise

问题 does anybody know how to create an abstract method in staruml 5.0? The UML standard says that such a method should be italic, but it seems that is not possible in staruml 5.0 for a single method? please help me :D 回答1: As depicted in the attached, you just have to select your method on the "model explorer" and then set it as "IsAbstract" on the properties tab. I just would to know why you use this modeler which have not been release since 2005? Regards, EBR 来源： https://stackoverflow.com

问题 I am trying to design one Abstract class and method in Android and call those methods by extending the class from my parent Activity class but i don't how to call my abstract method. MyCode : MainActivity.java public class MainActivity extends MyActivity { @Override public void onTest() { Log.d("MyLog", "onTest"); } } MyActivity.java public abstract class MyActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState);

问题 I'm reading the code that package time , and then I want to know how the func After(d Duration) <-chan Time works. I found the code follows: func After(d Duration) <-chan Time { return NewTimer(d).C } func NewTimer(d Duration) *Timer { c := make(chan Time, 1) t := &Timer{ C: c, r: runtimeTimer{ when: nano() + int64(d), f: sendTime, arg: c, }, } startTimer(&t.r) return t } So I found the definition of startTimer - it's so weird that function startTimer does not have a function body. func

问题 I've been asked this question and am frankly stumped: Instead of writing abstract methods we could try to fake them with exceptions, like this: public int someMethod(int someparameter) { throws new RuntimeException("unimplemented"); } What would be the purpose of doing this and can anyone provide an example of code for an abstract method that the above is trying to fake? Any help is greatly appreciated. Thank you. 回答1: I can think of one (possibly) valid use case: You have an abstract class,

问题 Okay so basically I have the following problem: I'm trying to have an abstract class inherit another abstract class that has an abstract method, but I don't want to implement the abstract method in either of them because a third class inherits from both of them: public abstract class Command { public abstract object execute(); } public abstract class Binary : Command { public abstract object execute(); //the issue is here } public class Multiply : Binary { public override object execute() { /