2-13 类中的访问器和构造类型

访问器

类的访问属性包括 private、public、 protected。
public：默认；类内外都可以访问
private：类内可访问
protected：类内和继承类可访问

例子
public

class Person {
    public name: string 
    public say(){
        console.log(this.name) //类内
    }
 }
const person1 = new Person()
person1.name = 'mtg'  //类外

private

class Person {
    private name: string 
    private say(){
        console.log(this.name) //类内
    }
}
const person1 = new Person()
person1.name = 'mtg'  //类外 报错

protected

class Person {
    protected name: string 
    protected say(){
        console.log(this.name) //类内
    }
}
class Teacher extends Person {
    protected sayBye(){
        this.name //继承
    }
}
const person1 = new Person()
person1.name = 'mtg'  //类外 报错

构造器constructor()

构造函数在被实例化的时候自动执行constructor（），在实例化时传递传递参数。

class Person {
    public name:string
    constructor(str:name){
        this.name=name
    }
}
const Teacher = new Person（'mtg')
Teacher.name //mtg

上述构造函数中，需要首先定义name。可以简化上述写法：

class Person {
    constructor(public name:string){ }
}
const Teacher = new Person'mtg')
Teacher.name //mtg

当子类继承类，也要构造器时，需要在子类中手动调super（），通过super向父类传。

class Person {
    constructor(public name:string){ }
}
class Teacher extends Person {
    constructor(public age:number){
        super('mtg')
     }
}
const teacher = new Teacher(18)
teacher.name // mtg
teacher.age //18