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.

Hash Config

This is a pattern for declaratively recording config information and having it available by key with fast retrieval.

Other patterns build on this.

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

It decouples configuration from logic.

Technical Specification

Declare keys for each config option.
Use a hash table to facilitate retrieval.

Code Signals

Config information is distributed throughout the code.

Rationale & Anti-Patterns

Leverage declarative statements for updates and maintenance.

When to Reach for It

Warnings

Example Code

// Function-Based JavaScript Example

const options = {
  exStringKey: 'Example String',
  exSwitchKey: true
};

// Provide a getter function to access the options
function getOption(key) {
  if(options[key]) return options[key];
  throw new Error(`Unrecognised option: ${key}`);
}

// Or just use them directly...
function doSomething() {
  if (options.exSwitchKey) {
    // Go left
  } else {
    // Go right
  }
  return `Processed ${options.exStringKey}`;
}

TS code needs checking and improving, just a rough start. Not using key properly for types.

// Class-Based TypeScript Example

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

class Processing {
  private options: Options = {
    exDataKey: 'Example String',
    exSwitchKey: true
  };

  // Provide a get method to access the options
  private static getOption(key: any): any {
    if(this.options[key]) return this.options[key];
    throw new Error(`Unrecognised option: ${key}`);
  }

  // Or just use them directly...
  private doSomething() {
    if (this.options.exSwitchKey) {
      // Go left
    } else {
      // Go right
    }
    return `Processed ${this.options.exDataKey}`;
  }
} 

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/hash-config

// Based on the "Hash Config" Pattern:
// https://docs.prescriptionfree.academy/patterns/hash-config

/*
 * ########################################################
 *   An implementation of the "Hash Config" pattern from
 * the Prescription Free Academy's Software Pattern Library
 * ########################################################
   https://docs.prescriptionfree.academy/patterns/hash-config
 * ########################################################
 */