superclass

问题 I'm trying to create classmethod constructors for a child class, but I cannot initialize the instance properly. I have read many blogs and answers on this site and even tried exactly what some other people have posted, still to no avail. Hopefully I'm missing something really simple. Basic example of what I'm trying: class A(object): def __init__(self, foo): self.foo = foo class B(A): @classmethod def make_new(cls): super(B, cls).__init__('bar') foobar = B.make_new() I keep getting unbound

问题 I'm trying to create classmethod constructors for a child class, but I cannot initialize the instance properly. I have read many blogs and answers on this site and even tried exactly what some other people have posted, still to no avail. Hopefully I'm missing something really simple. Basic example of what I'm trying: class A(object): def __init__(self, foo): self.foo = foo class B(A): @classmethod def make_new(cls): super(B, cls).__init__('bar') foobar = B.make_new() I keep getting unbound

问题 A) Class Parent4{ private I18nUtils i18n; //-----------Here Nullpointerexception occur---------------- public Parent4(){ SetText(i18n.getText("HELLO"); } } B) Class Parent3 extends Parent4{ private I18nUtils i18n; } C) Class ParentParent2 extends Parent3{ private I18nUtils i18n; } D) Class Parent extends ParentParent2{ private I18nUtils i18n; } E) Class Child extends Parent{ protected method_name(){ //.......DO Something...... } } My Test Class: public testclass{ Class cls = Class.forName(

问题 In the following code- class Mammal { String name = "furry "; String makeNoise() { return "generic noise"; } } class Zebra extends Mammal { String name = "stripes "; String makeNoise() { return "bray"; } } public class ZooKeeper { public static void main(String[] args) { new ZooKeeper().go(); } void go() { Mammal m = new Zebra(); System.out.println(m.name + m.makeNoise()); Zebra z = new Zebra(); System.out.println(z.name + z.makeNoise()); } } Both objects ( m and z ), if I see in debug

问题 In the following code- class Mammal { String name = "furry "; String makeNoise() { return "generic noise"; } } class Zebra extends Mammal { String name = "stripes "; String makeNoise() { return "bray"; } } public class ZooKeeper { public static void main(String[] args) { new ZooKeeper().go(); } void go() { Mammal m = new Zebra(); System.out.println(m.name + m.makeNoise()); Zebra z = new Zebra(); System.out.println(z.name + z.makeNoise()); } } Both objects ( m and z ), if I see in debug

问题 I have subclassed NSException class to create CustomException class. Whenever I catch an exception in code (in @catch), i want to initialize an object of CustomException (subclass of NSException) with the object of NSException that is passed as a parameter to @catch. Something like this @catch (NSException * e) { CustomException * ex1=[[CustomException alloc]initWithException:e errorCode:@"-11011" severity:1]; } I tried doing it by passing the NSException object to the init method of

问题 I am trying to figure out my superclass mismatch error. All the posts I've read about this describe the problem as being that User is defined twice as a class in my application. In my case, it isn't defined twice. I have a services folder and within that I have a user folder (for user service classes). In that user folder, I have a file called organisation_mapper_service.rb, with: class User < ActiveRecord::Base class OrganisationMapperService def self.call(user: u) new(user: user).call end

问题 I am trying to figure out my superclass mismatch error. All the posts I've read about this describe the problem as being that User is defined twice as a class in my application. In my case, it isn't defined twice. I have a services folder and within that I have a user folder (for user service classes). In that user folder, I have a file called organisation_mapper_service.rb, with: class User < ActiveRecord::Base class OrganisationMapperService def self.call(user: u) new(user: user).call end

问题 I want to make a superclass of Num, called Linear class Linear a where add :: a -> a -> a instance (Num a) => Linear a where add = (+) I get the error : Illegal instance declaration for `Linear a' (All instance types must be of the form (T a1 ... an) where a1 ... an are *distinct type variables*, and each type variable appears at most once in the instance head. Use -XFlexibleInstances if you want to disable this.) In the instance declaration for `Linear a' From what I understand, something

问题 I want to use a superclass sort which uses a subclass compare function. I've tried to distill the nature of the question in the following code. This isn't the "production" code, but is presented here for illustration. It's tested. #!/usr/bin/perl # $Id: foo,v 1.10 2019/02/23 14:14:33 bennett Exp bennett $ use strict; use warnings; package Fruit; use Scalar::Util 'blessed'; sub new { my $class = shift; my $self = bless({}, $class); $self->{itemList} = []; warn "Called with class ", blessed