javascript - 在 typescript 中获取类的属性

Question

我有以下类(class):

export class Test {

        private _rowsCount: string;
        public get RowsCount(): string {
            return this._rowsCount;
        };
        public set RowsCount(value: string) {
            this._rowsCount = value;
        };

        private _rowsCount2: string;
        public get RowsCount2(): string {
            return this._rowsCount2;
        };
        public set RowsCount2(value: string) {
            this._rowsCount2 = value;
        };
    }

我需要遍历特定类中的属性，我尝试了以下方法:

Object.keys(this).forEach((key)=> {
    console.log(key);
});

但是问题是这个遍历 private 字段，我也尝试了以下我得到了所有的 methods 和 properties:

    for (var property in this) {
        if (this.hasOwnProperty(property)) {
            console.log(property);                
        }
    }

有没有人有解决办法？

谢谢!

Answer 1

如果您只需要获取 getters/setters，那么您需要执行如下操作:

class Test {
    ...

    public static getGetters(): string[] {
        return Object.keys(this.prototype).filter(name => {
            return typeof Object.getOwnPropertyDescriptor(this.prototype, name)["get"] === "function"
        });
    }

    public static getSetters(): string[] {
        return Object.keys(this.prototype).filter(name => {
            return typeof Object.getOwnPropertyDescriptor(this.prototype, name)["set"] === "function"
        });
    }
}

Test.getGetters(); // ["RowsCount", "RowsCount2"]
Test.getSetters(); // ["RowsCount", "RowsCount2"]

( code in playground )

---

您可以将静态方法放在基类中，然后当您扩展它时，子类也将拥有这些静态方法:

class Base {
    public static getGetters(): string[] {
        return Object.keys(this.prototype).filter(name => {
            return typeof Object.getOwnPropertyDescriptor(this.prototype, name)["get"] === "function"
        });
    }

    public static getSetters(): string[] {
        return Object.keys(this.prototype).filter(name => {
            return typeof Object.getOwnPropertyDescriptor(this.prototype, name)["set"] === "function"
        });
    }
}

class Test extends Base {
   ...
}

Test.getGetters(); // work the same

( code in playground )

如果你想让这些方法成为实例方法，那么你可以这样做:

class Base {
    public getGetters(): string[] {
        return Object.keys(this.constructor.prototype).filter(name => {
            return typeof Object.getOwnPropertyDescriptor(this.constructor.prototype, name)["get"] === "function"
        });
    }

    public getSetters(): string[] {
        return Object.keys(this.constructor.prototype).filter(name => {
            return typeof Object.getOwnPropertyDescriptor(this.constructor.prototype, name)["set"] === "function"
        });
    }
}

变化在于，您使用的不是 this.prototype，而是 this.constructor.prototype。
然后你只需:

let a = new Test();
a.getGetters(); // ["RowsCount", "RowsCount2"]

( code in playground )

---

编辑

根据@Twois 的评论，他指出在以 es6 为目标时它不会工作，这里有一个可以工作的版本:

class Base {
    public static getGetters(): string[] {
        return Reflect.ownKeys(this.prototype).filter(name => {
            return typeof Reflect.getOwnPropertyDescriptor(this.prototype, name)["get"] === "function";
        }) as string[];
    }

    public static getSetters(): string[] {
        return Reflect.ownKeys(this.prototype).filter(name => {
            return typeof Reflect.getOwnPropertyDescriptor(this.prototype, name)["set"] === "function";
        }) as string[];
    }
}

主要区别:使用 Reflect.ownKeys(this.prototype) 而不是 Object.keys(this.prototype)。