面向对象编程中最重要的概念之一就是继承，继承使无涯教程可以用另一个类来定义一个类，这使创建和维护应用程序变得更加容易，这也提供了重用代码功能和快速实现时间的机会。
创建类时，程序员可以指定新类应继承现有类的成员，而不必编写全新的数据成员和成员函数。此现有类称为基类，而新类称为子类。
基类和子类
子类继承基类的成员，并拥有自己的成员，子类使用 inherit 关键字定义，如下所示-
type MyDerived(...) = inherit MyBase(...)
在F#中，一个类最多可以有一个直接基类，如果未使用 inherit 关键字指定基类，则该类隐式继承自对象(Object)。
type Person(name) = member x.Name = name member x.Greet() = printfn "Hi, I'm %s" x.Name type Student(name, studentID : int) = inherit Person(name) let mutable _GPA = 0.0 member x.StudentID = studentID member x.GPA with get() = _GPA and set value = _GPA <- value type Teacher(name, expertise : string) = inherit Person(name) let mutable _salary = 0.0 member x.Salary with get() = _salary and set value = _salary <- value member x.Expertise = expertise //using the subclasses let p = new Person("Mohan") let st = new Student("Zara", 1234) let tr = new Teacher("Mariam", "Java") p.Greet() st.Greet() tr.Greet()
编译并执行程序时，将产生以下输出-
Hi, I'm Mohan Hi, I'm Zara Hi, I'm Mariam
覆盖方法
F#中的方法默认情况下不可覆盖。
要覆盖派生类中的方法，您必须使用 abstract 和 default 关键字将方法声明为可覆盖，如下所示:
type Person(name) = member x.Name=name abstract Greet : unit -> unit default x.Greet()=printfn "Hi, I'm %s" x.Name
现在，可以在派生类中覆盖Person类的 Greet 方法。以下示例演示了这一点-
type Person(name) = member x.Name = name abstract Greet : unit -> unit default x.Greet() = printfn "Hi, I'm %s" x.Name type Student(name, studentID : int) = inherit Person(name) let mutable _GPA = 0.0 member x.StudentID = studentID member x.GPA with get() = _GPA and set value = _GPA <- value override x.Greet() = printfn "Student %s" x.Name type Teacher(name, expertise : string) = inherit Person(name) let mutable _salary = 0.0 member x.Salary with get() = _salary and set value = _salary <- value member x.Expertise = expertise override x.Greet() = printfn "Teacher %s." x.Name //使用子类 let p = new Person("Mohan") let st = new Student("Zara", 1234) let tr = new Teacher("Mariam", "Java") //default Greet p.Greet() //Overriden Greet st.Greet() tr.Greet()
编译并执行程序时，将产生以下输出-
Hi, I'm Mohan Student Zara Teacher Mariam.
抽象类
您不能创建抽象类的，因为该类尚未完全实现。
[<AbstractClass>] type Person(name) = member x.Name = name abstract Greet : unit -> unit type Student(name, studentID : int) = inherit Person(name) let mutable _GPA = 0.0 member x.StudentID = studentID member x.GPA with get() = _GPA and set value = _GPA <- value override x.Greet() = printfn "Student %s" x.Name type Teacher(name, expertise : string) = inherit Person(name) let mutable _salary = 0.0 member x.Salary with get() = _salary and set value = _salary <- value member x.Expertise = expertise override x.Greet() = printfn "Teacher %s." x.Name let st = new Student("Zara", 1234) let tr = new Teacher("Mariam", "Java") //Overriden Greet st.Greet() tr.Greet()
编译并执行程序时，将产生以下输出-
Student Zara Teacher Mariam.
