OOP Design Question

Question

Got this interview question which i'm wondering about:

A software company designed an app that manages employees and, among other functions, calculates Salary.

The current structure which fits the customer's requirements is:

abstract Class Employee;
Class Manager extends Employee;
Class Engineer extends Employee;

The customer would now like to add the ability to support different types of salary calculations for employees who work on an hourly wage, monthly salary. Both Engineer and Manager can be either.

The customer also notified the software company that they will add a number of other types of salaries in the future.

The Question - How would you design this? Does if fall in any design pattern solution?

Thanks!

Doc Brown · Accepted Answer · 2011-09-25 07:12:30Z

7

Apply the strategy pattern:

http://en.wikipedia.org/wiki/Strategy_pattern

Make "Salary_Calculation" a strategy associated to Employee. "Salary_Calculation" should be an interface or an abstract base class, and each salary calculation model is a subclass of that.

edited Sep 25, 2011 at 7:12

answered Sep 25, 2011 at 6:54

Doc Brown

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2 Comments

Turd Over a year ago

Thank you. That was my hunch. I'll wait for an hour to see other opinions. BTW - Isn't this more of a delegate than strategy? p2p.wrox.com/book-professional-php-design-patterns/…

Doc Brown Over a year ago

Using the "Delegation pattern" here means, the Employee does not calculate the salary by itself but delegates this to the strategy object. It does not say anything about different salary calculation models. "Strategy pattern" means you will have different subclasses, one for each type of salary calculation. It does not define where the calculation takes place (the different subclasses may just provide metadata to help "Employee" doing the right calculation). Both patterns will be applicable here, thouh I thing "strategy" is what you interviewer was after.

John W · Accepted Answer · 2011-09-25 06:59:00Z

1

Add a SalaryCalculator interface and instantiate a SalaryCalculator object during the Employee object's construction using the salary type. The SalaryCalculaotr object will take care of salary calculations for each salary type.

answered Sep 25, 2011 at 6:59

John W

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