TypeScript-类和接口

类实现接口

• 只要实现的某一个接口, 那么就必须实现接口中所有的属性和方法

错误示例：

interface PersonInterface {
    name: string;

    say(): void;
}

class Person implements PersonInterface {
    name: string = 'BNTang';
}

let p = new Person();
p.say();

正确示例：

interface PersonInterface {
    name: string;

    say(): void;
}

class Person implements PersonInterface {
    name: string = 'BNTang';

    say(): void {
        console.log(`我的名字叫:${this.name}`);
    }
}

let p = new Person();
p.say();

接口继承类

定义一个 Person 类如下：

class Person {
    name: string = 'BNTang';
    age: number = 18;

    say(): void {
        console.log(`name = ${this.name}, age = ${this.age}`);
    }
}

• 只要一个接口继承了某个类, 那么就会继承这个类中所有的属性和方法
• 但是只会继承属性和方法的 声明, 不会继承属性和方法的 实现

class Person {
    name: string = 'BNTang';
    age: number = 18;

    say(): void {
        console.log(`name = ${this.name}, age = ${this.age}`);
    }
}

interface PersonInterface extends Person {
    gender: string;
}

class Student implements PersonInterface {
    gender: string = 'male';
    name: string = 'zs';
    age: number = 18;

    say(): void {
        console.log(`name = ${this.name}, age = ${this.age}, gender = ${this.gender}`);
    }
}

let stu = new Student();
stu.say();

• 如果接口继承的类中包含了 protected 的属性和方法, 那么就只有这个类的 子类 才能实现这个接口

• 包含 protected 属性的情况

错误示例：

class Person {
    protected name: string = 'BNTang';
    age: number = 18;

    say(): void {
        console.log(`name = ${this.name}, age = ${this.age}`);
    }
}

interface PersonInterface extends Person {
    gender: string;
}

class Student implements PersonInterface {
    gender: string = 'male';
    name: string = 'zs';
    age: number = 18;

    say(): void {
        console.log(`name = ${this.name}, age = ${this.age}, gender = ${this.gender}`);
    }
}

let stu = new Student();
stu.say();

正确示例：

class Person {
    protected name: string = 'BNTang';
    age: number = 18;

    say(): void {
        console.log(`name = ${this.name}, age = ${this.age}`);
    }
}

interface PersonInterface extends Person {
    gender: string;
}

class Student extends Person implements PersonInterface {
    gender: string = 'male';
    name: string = 'zs';
    age: number = 18;

    say(): void {
        console.log(`name = ${this.name}, age = ${this.age}, gender = ${this.gender}`);
    }
}

let stu = new Student();
stu.say();

• 包含 protected 方法的情况

错误示例：

class Person {
    name: string = 'BNTang';
    age: number = 18;

    protected say(): void {
        console.log(`name = ${this.name}, age = ${this.age}`);
    }
}

interface PersonInterface extends Person {
    gender: string;
}

class Student implements PersonInterface {
    gender: string = 'male';
    name: string = 'zs';
    age: number = 18;

    say(): void {
        console.log(`name = ${this.name}, age = ${this.age}, gender = ${this.gender}`);
    }
}

let stu = new Student();
stu.say();

正确示例：

class Person {
    name: string = 'BNTang';
    age: number = 18;

    protected say(): void {
        console.log(`name = ${this.name}, age = ${this.age}`);
    }
}

interface PersonInterface extends Person {
    gender: string;
}

class Student extends Person implements PersonInterface {
    gender: string = 'male';
    name: string = 'zs';
    age: number = 18;

    say(): void {
        console.log(`name = ${this.name}, age = ${this.age}, gender = ${this.gender}`);
    }
}

let stu = new Student();
stu.say();