You’re reading our Software Patterns collection. It features useful patterns for learning to write software.

This document is a working draft. It is live published as it is written and edited. Dec/Jan 2024.

Declarative Sets

This is a pattern to provide a single processing interface able to complete processing based on a set of options.

This pattern can be used in cases where there is repeated code around the same theme, in order to reduce it to a single interface.

It makes case processing configurable which simplifies management and makes it less error-prone.

It decouples configuration from logic.

Other patterns build on this pattern.

Technical Specification

Define options for processing.
Abstract a processing interface based on the options.

Code Signals

Rationale & Anti-Patterns

Decouple processing logic from options for that process.

Leverage a clearly defined interface for updates and maintenance.

When to Reach for It

Warnings

Example Code

// Function-Based JavaScript Example

TS code needs checking and improving, just a rough start.

// Class-Based TypeScript Example

type ProcessingOptions = {
  exDataKey: string;
  exSwitchKey: boolean;
};

class Processing {
  public static process(options: ProcessingOptions, data: any): any {
    // TODO: Process data based on options
  }
}

Processing.process({
  exDataKey: ‘Example String’,
  exSwitchKey: true
}, data);

Example Implementation

Attribution

If you make use of this pattern, please consider adding an attribution to your code or elsewhere.

Here are some suggestions…

// https://docs.prescriptionfree.academy/patterns/declarative-options

// Based on the "Declarative Options" Pattern:
// https://docs.prescriptionfree.academy/patterns/declarative-options

/*
 * ###############################################################
 *   An implementation of the "Declarative Options" pattern from
 * the Prescription Free Academy's Software Pattern Library
 * ###############################################################
   https://docs.prescriptionfree.academy/patterns/declarative-options
 * ###############################################################
 */

Open Source Examples

Examples found in established open source projects.

From Next.js. See the packages object and the following for loop. Lines 19 to 31. It’s a partial implementation of the pattern described here.
GitHub vercel/next.js at 5259eb

This highly complex example from Angular is littered with this pattern throughout the processing that is being done of command line compilation and configuration options.
GitHub angular/angular at 0e05d2

Links are to specific points in time in case code is changed later. Please share other examples where you find them so they can be added here.

Comments

Another data structure could be used for option lookup equally effectively. There are many variations on this kind of approach. Other pattern entries are being worked on to demonstrate that.

The basic idea is to separate processing details from processing logic where the process needs to be done in different yet similar ways, so it can be abstracted and result in less code that shows the logic involved rather than details of the options.