inheritance

问题 I'm trying to migrate my application from the beautiful Logrus (very helpful for debug) and introducing the Uber log framework Zap. With Logrus, i can initialize the logger only once and reuse it from other Go file, an example: package main import( // Print filename on log filename "github.com/onrik/logrus/filename" // Very nice log library log "github.com/sirupsen/logrus" ) func main(){ // ==== SET LOGGING Formatter := new(log.TextFormatter) Formatter.TimestampFormat = "Jan _2 15:04:05

问题 I'm trying to migrate my application from the beautiful Logrus (very helpful for debug) and introducing the Uber log framework Zap. With Logrus, i can initialize the logger only once and reuse it from other Go file, an example: package main import( // Print filename on log filename "github.com/onrik/logrus/filename" // Very nice log library log "github.com/sirupsen/logrus" ) func main(){ // ==== SET LOGGING Formatter := new(log.TextFormatter) Formatter.TimestampFormat = "Jan _2 15:04:05

问题 I want to write an extension method for a collection of objects that uses base class as a type requirement. I understand this is not necessarily the best way to do things, but I am curious because I'm interested in learning the nuances of the language. This example explains what I would like to do. public class Human { public bool IsHappy { get; set; } } public class Man : Human { public bool IsSurly { get; set; } } public class Woman : Human { public bool IsAgreeable { get; set; } } public

问题 Is there a way to force classes in Java to have public static final field (through interface or abstract class)? Or at least just a public field? I need to make sure somehow that a group of classes have public static final String TYPE = "..."; in them. 回答1: No, you can't. You can only force them to have a non-static getter method, which would return the appropriate value for each subclass: public abstract String getType(); If you need to map each subclass of something to a value, without the

问题 I have the following error in my code: error: allocating an object of abstract class type 'Material' I don't know how to handle this case. I'm aware that std::make_unique performs an allocation, so it can't allocate the object of type Material , but I don't know how to correct it. #include <iostream> #include <memory> struct Material { Material() = default; virtual int get_color() const = 0; }; struct Basic : public Material { Basic() = default; virtual int get_color() const override { return

问题 I have the following error in my code: error: allocating an object of abstract class type 'Material' I don't know how to handle this case. I'm aware that std::make_unique performs an allocation, so it can't allocate the object of type Material , but I don't know how to correct it. #include <iostream> #include <memory> struct Material { Material() = default; virtual int get_color() const = 0; }; struct Basic : public Material { Basic() = default; virtual int get_color() const override { return

问题 How can I access base class variable from a child method? I'm getting a segmentation fault. class Base { public: Base(); int a; }; class Child : public Base { public: void foo(); }; Child::Child() :Base(){ void Child::foo(){ int b = a; //here throws segmentation fault } And in another class: Child *child = new Child(); child->foo(); 回答1: It's not good practice to make a class variable public. If you want to access a from Child you should have something like this: class Base { public: Base():

问题 YAML has inheritance. The most clear example I have ever seen is here: http://blog.101ideas.cz/posts/dry-your-yaml-files.html I need something more complex: I need to override object's object's property. Here is an example: database: &default server: ip: 192.168.1.5 port: 2000 db_name: test user: name: root password: root # database foo differs from default by only its port and user password foo_database: <<: *default server: port: 2001 db_name: foo user: password: foo_root I want to get this

问题 I am trying to understand how class inheritance works in Python 3, in particular how private fields interact with local and inherited methods. Here are some examples to illustrate the issue. First, if a variable var in the Superclass is public, then any method in the Subclass will also be able to alter it: class Superclass: var = 1 def getVar(self): print(self.var) class Subclass(Superclass): def __init__(self): self.var = 123 my_object = Subclass() my_object.getVar() # outputs 123 The same

问题 I am trying to understand how class inheritance works in Python 3, in particular how private fields interact with local and inherited methods. Here are some examples to illustrate the issue. First, if a variable var in the Superclass is public, then any method in the Subclass will also be able to alter it: class Superclass: var = 1 def getVar(self): print(self.var) class Subclass(Superclass): def __init__(self): self.var = 123 my_object = Subclass() my_object.getVar() # outputs 123 The same