javascript - 要求解决未定义

Question

我有以下类结构。

员工服务.js

const {EmployeeRequestExecutor} = require('./EmployeeRequestExecutor');

class EmployeeService {
    fulfill(request){
        EmployeeRequestExecutor.delegateEmployeeRequest(request);
    }
}

module.exports = {EmployeeService};

员工请求执行器.js

const {HelpfulEmployee} = require('./HelpfulEmployee');

class EmployeeRequestExecutor {
    static delegateEmployeeRequest(request){
        let employee = new HelpfulEmployee();
        employee.work(request);
    }

    static executeEmployeeRequest(request){
        console.log('Executed', request);
    }
}

module.exports = {EmployeeRequestExecutor};

HelpfulEmployee.js

const {EmployeeRequestExecutor} = require('./EmployeeRequestExecutor');

class HelpfulEmployee {
    work(request){
        EmployeeRequestExecutor.executeEmployeeRequest(request);
    }
}

module.exports = {HelpfulEmployee};

如果我们这样做

let employeeService = new EmployeeService();
employeeService.fulfill(request);

我们得到 类型错误:无法读取 HelpfulEmployee.js 中未定义的属性“executeEmployeeRequest”:5:33

为什么HelpfulEmployee.js中这样的调用结构EmployeeRequestExecutor是未定义的？

Answer 1

HelpfulEmployee 和 EmployeeRequestExecutor 之间存在循环依赖(它们都需要彼此)。 循环依赖大多数时候是由类设计问题引起的。要修复它们，您应该重新考虑对象之间的信息流。

这是一个选项，但还有更多选项:

const {HelpfulEmployee} = require('./HelpfulEmployee');

class EmployeeRequestExecutor {
    static delegateEmployeeRequest(request){
        let employee = new HelpfulEmployee();
        let requestExecutor = new EmployeeRequestExecutor();
        employee.work(request, requestExecutor);
    }

    executeEmployeeRequest(request){
        console.log('Executed', request);
    }
}

module.exports = {EmployeeRequestExecutor};

class HelpfulEmployee {
    work(request, requestExecutor){
        requestExecutor.executeEmployeeRequest(request);
    }
}

module.exports = {HelpfulEmployee};