derived

Overriding an abstract property with a derived return type in c#

由 北慕城南 提交于 2021-02-06 09:41:14
问题 I have four classes. Request, DerivedRequest, Handler, DerivedHandler. The Handler class has a property with the following declaration: public abstract Request request { get; set; } The DerivedHandler needs to override this property so that it returns DerivedRequest instead: public override DerivedRequest request { get; set; } Does anyone have any ideas about how to make this work? 回答1: This isn't really a good way to structure things. Do one of the following 1) Just don't change the return

Overriding an abstract property with a derived return type in c#

由 倾然丶 夕夏残阳落幕 提交于 2021-02-06 09:41:05
问题 I have four classes. Request, DerivedRequest, Handler, DerivedHandler. The Handler class has a property with the following declaration: public abstract Request request { get; set; } The DerivedHandler needs to override this property so that it returns DerivedRequest instead: public override DerivedRequest request { get; set; } Does anyone have any ideas about how to make this work? 回答1: This isn't really a good way to structure things. Do one of the following 1) Just don't change the return

[golang note] 匿名组合

由 ∥☆過路亽．° 提交于 2020-04-06 19:15:58
匿名组合 golang也提供了继承机制，但采用组合的文法，因此称为匿名组合。与其他语言不同， golang很清晰地展示出类的内存布局是怎样的。 • 非指针方式组合 ▶ 基本语法 // 基类 type Base struct { // 成员变量 } func (b *Base) 函数名(参数列表) (返回值列表) { // 函数体 } // 派生类 type Derived struct { Base // 成员变量 } func (b *Derived) 函数名(参数列表) (返回值列表) { // 函数体 } ▶ 继承规则 √ 在派生类没有改写基类的成员方法时，相应的成员方法被继承。 √ 派生类可以直接调用基类的成员方法，譬如基类有个成员方法为Base.Func()，那么Derived.Func()等同于Derived.Base.Func() √ 倘若派生类的成员方法名与基类的成员方法名相同，那么基类方法将被覆盖或叫隐藏，譬如基类和派生类都有成员方法Func()，那么Derived.Func()将只能调用派生类的Func()方法，如果要调用基类版本，可以通过Derived.Base.Func()来调用。 ▪ 示例如下 package main import "fmt" type Base struct { } func (b *Base) Func1() { fmt

认识class Class及其应用

由 有些话、适合烂在心里 提交于 2020-03-10 18:09:44
一． Class类 1. class　Class对象描述了运行中的classes和interfaces。通过Class对象可以取得运行中的classes和interfaces的相关信息。 2. 每个class都有一个相应的Class对象。每个class的Class对象存储于编译后的class所在的文件中。所以，当JVM装载一个.class文件时就会装载一个Class对象。所以，一个class只有一个Class对象。 二． Class类的基本应用 1. 如何获取一个class的Class对象 1.1 通过Class.forName(classname)方法，该方法接收一个String参数，用以指定要生成哪个class的Class对象.，如Class.forName(“Dog”)。 1.2 通过类字面常量（class　literals）来获得。 1) 字面常量的形式为：classname.class。如Dog.class。 2) 对于基本类开，每种基本类型的外覆类都有一个名为TYPE的标准数据，能够产生一个指向相应的基本类型的Class对象的reference。如int.class等同于Integer.TYPE。 1.3 通过Object.getClass()方法来获得，如 Dog dog = new Dog(); dog.getClass(); 1.4 一个产生Class对象的例子

Subscribe to a doc using Svelte / RxJs / RxFire. How can I update the subscription

由 拜拜、爱过 提交于 2020-02-06 06:08:28
问题 I use a derived store in the code below. It feels like a strange construct because I only use the derived construct for the dynamic $session dependency and to get the normData. But not with $norm. I use $norm only once to kick off the derived store. Nevertheless it seem to work fine. But I have to renew the subscription if the $session changes. Is it possible to update the RxFire / RxJs subscription without unsubscribing first? let normDocRef = null; let normData = null; let normSubscription

Subscribe to a doc using Svelte / RxJs / RxFire. How can I update the subscription

由 吃可爱长大的小学妹 提交于 2020-02-06 06:07:26
问题 I use a derived store in the code below. It feels like a strange construct because I only use the derived construct for the dynamic $session dependency and to get the normData. But not with $norm. I use $norm only once to kick off the derived store. Nevertheless it seem to work fine. But I have to renew the subscription if the $session changes. Is it possible to update the RxFire / RxJs subscription without unsubscribing first? let normDocRef = null; let normData = null; let normSubscription

C++中的类型判断typeid()操作与java中的 instanceof 做比较

由 烈酒焚心 提交于 2020-02-02 00:52:16
这是RTTI（运行阶段类型识别）的问题，c++有三个支持RTTI的元素： 1. dynamic_cast 操作符 如果可能的话，dynamic_cast操作符将使用一个指向基类的指针来生成一个指向派生类的指针；否则，该操作符返回空指针。这是最常用的 RTTI组件，它不能回答“指针指向的是哪类对象”这样的问题，但他能回答“是否可以安全地将对象的地址赋给特定类型的指针”这样的问题。如： class A{} class B: public A{} class C: public B{} 然后有下面的指针： A *a = new A; B *b = new B; C *c = new C; 则： C *cc1 = dynamic_cast<C*>(c); //安全 C *cc2 = dynamic_cast<C*>(a); //cc2是空指针 C *cc3 = dynamic_cast<c*>(b); //cc3是空指针 B *bb = dynamic_cast<C*>(b); //安全 注：只能将此RTTI用于包含虚函数的类层次结构，原因在于只有对于这种类层次结构，才应该将派生类对象的地址赋给基类指针。 2. typeid操作符 3. type_info结构,(须包含头文件<typeinfo>) class A{} class B: public A{} class C: public

Derived class explicit base constructor call

由 强颜欢笑 提交于 2020-01-23 18:21:15
问题 I am trying to learn C#. The below data is from a Microsoft C# help website. I don't understand this statement, "If a base class does not offer a default constructor, the derived class must make an explicit call to a base constructor by using base." I thought that if there is no default constructor for a class, C# will automatically assign default values to int, char or whatever is declared in a class. If a base class does not have a constructor and it has a child class, does the rule

Derived class explicit base constructor call

由 心已入冬 提交于 2020-01-23 18:21:06
问题 I am trying to learn C#. The below data is from a Microsoft C# help website. I don't understand this statement, "If a base class does not offer a default constructor, the derived class must make an explicit call to a base constructor by using base." I thought that if there is no default constructor for a class, C# will automatically assign default values to int, char or whatever is declared in a class. If a base class does not have a constructor and it has a child class, does the rule

C++继承

由 早过忘川 提交于 2020-01-22 21:34:51
1. C++继承语法 class Derived [: [private|protected|public] Base1, ...] 如果没有指定private、protected或public，则默认是private继承。如果是用struct来定义类，那么默认就是public继承。 使用这里的private、protected和public是用来控制Derived类的对象和子类对Base1等父类的成员的访问，而Derived类内部对与Base1等父类的成员的访问则只受父类的控制。 2. C++支持多重继承，但是这样容易出现菱形继承，容易产生歧义。 关于菱形继承，这一有一篇文章可以参考 。 3. C++中，子类的构造函数应该调用父类的构造函数来完成从父类继承的成员的初始化。语法 Derived(base_x, derived_y):Base(x), y(derived_y){ ... } 推荐使用父类的构造函数来初始化父类成员，即使有些情况下，父类的成员子类都可以访问，能在子类的构造函数函数体内部初始化。 4. C++中，推荐将父类和子类的析构函数设置为virtual函数，这样使用指针和引用的时候程序能够自动地找到正确的析构函数去执行。 5. 父类中定义了类静态变量，子类继承父类之后和父类使用同一个静态变量。 6. 只有使用public限定的继承才能实现子到父的类型转换。 7.
订阅 derived