TypeScript 此表达式不可调用

Question

我确定这是简单的代码，但我遇到了奇怪的错误但没有答案。 我也确实从中查找了答案：get and set in TypeScript

但我的代码完全一样。但是当我设置实例的属性时出现这个错误：

This expression is not callable.
  Type 'String' has no call signatures

这是我的代码

/**
 * Class that use underscore name and get set syntax
 */
class Person {

    // can give any property name, use convention `_`
    private _fname: string;
    private _lname: string;

    constructor(first: string, last: string) {
        this._fname = first;
        this._lname = last;
    }

    public get firstname(): string {
        return this._fname;
    }

    public set firstname(first: string) {
        this._fname = first;
    }

    public get lastname(): string {
        return this._lname;
    }

    public set lastname(last: string) {
        this._lname = last;
    }

}

// create instance
let character = new Person("Laila", "Law-Giver");
console.log(`Jarl of Riften is ${character.firstname} ${character.lastname}`);

character.firstname("Saerlund");
console.log(`${character.firstname} ${character.lastname} is her son, who sides with the Empire.`);

character.firstname("Saerlund"); 有错误

这是什么意思？我看不出代码有什么问题。

Answer 1

您将firstname 声明为setter，并且为了为其分配新值，您应该执行以下操作：

character.firstname = "Saerlund";