Design pattern for different code behaviors according to different clients

Question

At my company, we have a solution composed of a WinForm (multiple per client) and an API (one per client). This solution is deployed on different clients that require the solution to behave differently according to their desires. The same code base must support UI customizations (client logo, buttons visibility) and functionality customizations (calling the same WebMethod with different flags).

Currently we manage this flexibility on the WinForm side by having an Organization class that contains all these customizations (flags). The API is totally client-agnostic. Thus, the WinForm's methods look like this:

this.Logo = CurrentOrganization.LogoImage;

API.GetProducts(Organization.UsesPagination);

In the past, we had conditional build directives scattered among the code:

#IF CLIENT_A
    API.GetProductsWithPagination();
#ELSE
    API.GetProducts();
#ENDIF

Today, we have a single zone with those conditional build directives that, according to the build configuration, instantiates the required Organization class. Afterwards, there are no more IFs, parameter passing.

I'm a bit worried this is not the best design or the most maintainable solution. I studied the State pattern... I guess the Organization is my strategy object, since it tells other methods how they should behave through flags.

Is there a better way?

Storing configurations on a DB table? (requires more requests to the API, which costs time)
Storing configurations on a *.config files? (someone can easily change the app behavior by editing the file)

Is getting data from a database for an api really that big of a problem? — JeffO
– JeffO, Commented Jul 21, 2015 at 17:47
The thing is: the local WinForm EXE calls » remote API which calls » DB — dialex
– dialex, Commented Jul 22, 2015 at 11:41

Doc Brown · Accepted Answer · 2015-07-21 14:29:15Z

First thing you should check is how many lines of code a typical Organization class implementation has, and how it is structured. If it has less than 100 lines of code, and the class consists mainly of properties providing some flags or data, do not worry. If it has more than 2000, and it contains a lot of business logic, you should consider to split it into smaller pieces, or to generalize some flags or properties. Nevertheless your Organization class can still be a facade to the configuration data.

Storing configurations on a DB table? Storing configurations on a *.config files?

Even if you use a DB table or a configuration file, you will still need an Organization object which loads the configuration from the DB table or configuration file into memory to provide those data to the rest of the program. This enables you or an admin or someone else to add new organizations, or to change features of existing organizations without actually changing the code. So use a DB table or a configuration file if you have that requirement - not because you want to achieve a better maintainability.

pietromenna · Accepted Answer · 2015-07-21 19:42:09Z

1

I think you are almost there. You are getting the State and the Strategy. The way of selecting maybe would be a Factory or a Builder maybe reading a configuration file or a database just as you pointed.

At the end it will depend on your own requirements, but the strategy mixed with the Factory or a Builder Pattern to create the object which contains the right policy on creation will help you to get rid of the conditionals builds directives.

edited Jul 21, 2015 at 19:42

answered Jul 21, 2015 at 14:24

pietromenna

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iluwatar · Accepted Answer · 2015-07-21 16:27:58Z

0

I would strive for data-driven design. This means that your code is driven by customer specific data. This data may be stored in database or configuration files or whatever suits you best. This way you don't have to build different binaries for each customer with the conditional build directives.

In cases where you need different behavior for different customers you can look up the desired behavior from the customer data and use Strategy pattern switch it during runtime.

answered Jul 21, 2015 at 16:27

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