Extending a Webapp - Include user and password_问答_开发者

They always talk about extendability and flexibility when writing code, but here I am wanting to expand my webapp and I have no idea how to do it.

What I have:

I have a completed webapp that works similarly to a calendar (though not exactly), a school has a list of teachers, each teacher has a number of tests assigned to him, the school gets a list of possible times for tests, and has to fit the teachers into the possible test times, using several rules. That much is DONE

What I want to do:

Now that the application is complete, I recieved a request to support a user/pass system, and every user will have a specific calendar that matches him (user == school in this context).

The problem:

I want to preform the shift with minimal code alteration (to the source classes). I can extend the source class, but that would mean

To change all the times the class is referred to in the code to the new name
Simply adding more code

The point is to have each user a database for his own.

LET ME JUST CLARIFY, MAKING THE USER PASS LOGIN SYSTEM IS NOT THE PROBLEM, THE PROBLEM IS TO EXTEND THE CODE TO ACCOMMODATE THE MULTIPLE USER ENVIRONMENT

Database Structure:

Fixed Tables:

teachers

id | name

Monthly Tables:

The program is updated each month, and history save is required, therefore these tables are added EVERY MONTH.

schedule_month_year - The actual schedule.

id | datetime | te开发者_运维百科acherid

requests_month_year - Contains the requests from the teachers (I want a test on dd/mm, or I don't want on dd/mm)

id | teacherid | wantsornot

teachers_month_year - Contains information about teachers and how many tests they have for this month.

teacherid | tests

I'm looking for good advice here, maybe I initially wrote my code wrong, in which case, how do you write code preparing for events you don't know that might happen? (The code I currently have was already re-written nearly from scratch because I was requested to add a change too large to accommodate).

Sometimes I get the idea that extensibility is a hyped up buzzword. It’s not really. It does have merit. However, many touting the benefits of extensibility leave the impression that you can extend an application with virtually no work. This illusion falls apart in the face of database interactions because changes/additions to a database structure invariably necessitate changes in code. The truth behind extensible software is that it’s not easy to extend; rather, it’s easier than the alternative.

In this specific case, Maxem has the right idea. The fact that it "requires a change of all queries, which is quite a lot" is inconsequential. Since you have a working app, the extra work entails only those things required to extend it as opposed to a complete rewrite/redesign. If all you have to do is add some databases and change some queries, then you’re in a good position.

how do you write code preparing for events you don't know that might happen?

Design principles and patterns seek to answer this very question.

You may also benefit from Agile software development which addresses the issue of changing requirements among other things.

I believe experience also plays a crucial role here. In the future, when you design an app intended for a single user, you’ll instinctively start thinking about how it might be extended to multiple users and design the app accordingly. Please understand that I’m not implying you’re inexperienced. My point here is that each new experience adds to your arsenal of techniques.

The point is to have each user a database for his own.

And why does that require any code change if every school is in its own database?

Anyways, what you have here is a typical multi tenant application. The usual way to go is to add the tenant identifier (in your case school) to more or less every table (class) and always filter by this tenant identifier.

Have n + 1 databases. (1 for the mapping of users to schools and the rest for the schools).
Create a database choosing class in your code.
Until a user is logged in use the mapping database.
When a user logs in retrieve their school and store it in the session.
Make the database choosing class use the correct database when the session is set.

You have to add a table where each teacher belongs to a school and another table where each user belongs to a school. After the user logged in you get the user id, with the user id you get the school and with the school you get the teachers you need. Now you only pass those teachers to the webapp. IF you did everything right in advance, you should have some templates which you fill with the teacher and schedule content. Not only fill those templates with the content from the user.

Then you don't need one database for each user.