如何在类公共函数和类变量上使用typeguards

class Animal {
    name: string;
    constructor(name: string) {
        this.name = name;
    }
}

class Dog extends Animal {
    breed: string;
    constructor(name: string, breed: string) {
        super(name);
        this.breed = breed;
    }
}

class Cat extends Animal {
    color: string;
    constructor(name: string, color: string) {
        super(name);
        this.color = color;
    }
}

function isDog(animal: Animal): animal is Dog {
    return (animal as Dog).breed !== undefined;
}

function isCat(animal: Animal): animal is Cat {
    return (animal as Cat).color !== undefined;
}

class Zoo {
    private animals: Animal[] = [];

    addAnimal(animal: Animal) {
        this.animals.push(animal);
    }

    listAnimals() {
        this.animals.forEach(animal => {
            if (isDog(animal)) {
                console.log(`Dog: ${animal.name}, Breed: ${animal.breed}`);
            } else if (isCat(animal)) {
                console.log(`Cat: ${animal.name}, Color: ${animal.color}`);
            } else {
                console.log(`Unknown animal: ${animal.name}`);
            }
        });
    }
}

const zoo = new Zoo();
zoo.addAnimal(new Dog("Buddy", "Golden Retriever"));
zoo.addAnimal(new Cat("Whiskers", "Black"));
zoo.listAnimals();

function isDog(animal: Animal): animal is Dog {
    return (animal as Dog).breed !== undefined;
}

function isDog(animal: Animal): animal is Dog {
    return animal.constructor === Dog;
}