老师，你全程就是敲代码，一点解释都没有，看得好累。
我现在仿造你得登录，写了如下代码。遇到问题了：

• 问题：参照你的方法写的装饰器，返回错误码，但是在login方法里面还是会被下面的body覆盖了接口返回。如果是这样的话，装饰器的作用就失效了。
• 期望：如果在装饰器里判断缺少必填属性，直接返回错误码，而不去执行方法里的接口返回。

请教老师如何做。

// decorator.ts
import _ from 'lodash';
const decorator = (middleware: any) =>
    (target: any, key: string, descriptor: any) => {
        const method = descriptor.value;
        descriptor.value = (ctx: any, next: any) => {
            middleware(ctx, next);
            return method.apply(target, [ctx, next]);
        };
        return descriptor;
    };

interface IRule {
    body?: string[];
    query?: string[];
    [propName: string]: any;
}
export const Required = (rules: IRule) => decorator(async (ctx: any, next: any) => {
    const request = ctx.request;
    let err: string[] = [];
    _.forEach(rules, (value: any, key) => {
        if (value) err = value.filter((v: any) => !_.has(request[key], v));
    });
    if (err.length) {
        ctx.body = {
            code: 412,
            msg: `${err.join(',')} is required`
        };
    }
    await next();
});

// member.ts
import { Required } from '../lib/decorator';

class Member {
    @Required({
        body: ['user', 'pass']
    })
    static async login (ctx: any, next: any) {
        console.log(ctx.body);
        return (ctx.body = {
            msg: '123',
            code: 1234
        });
    }
}

export default Member;