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Derivables

Table of Contents​

  1. Overview
  2. Imports and Dependencies
  3. Classes and Interfaces
  4. Methods and Functionality
  5. Usage (Additional)

Derivables - Derived Properties​

Derivables extension will listen to source properties changes and update the derived property's value. Usually, derived properties are also non-serializable (since it can be derived from data), therefore you can apply Ephemerals on it.

class DerivedTestClass {
  strVal = 'string';
  numVal = 5;
  derivedProp: string; /* DERIVED */
  derivedProp2: string; /* DERIVED EPHEM */
  constructor(init?: Partial<DerivedTestClass>) {
    defineOn(this, DerivedTestClass, lib => {
      lib.derivables.of(this, { /* options */ }, {
        derivedProp: (strVal, numVal) => strVal + numVal, // short format
        derivedProp2: { // long format, functionally the same as above (a little fatster in terms of perf)
          from: { strVal:1, numVal:1 },
          derive() { return this.strVal + this.numVal; }
        }
        ...
      lib.ephemerals.of(this, { derivedProp2: true, ...
  }
}

const d = new DerivedTestClass({ strVal: 'joined', numVal: 5 }));
console.log( d.derivedProp ); // 'joined5'
d.strVal = 'joined2_'; // updated source
d.numVal = 10;
console.log( d.derivedProp ); // 'joinedUpdated_10' automatically updated
console.log( JSON.stringify(d) ); // derivedProp2 not saved: {"strVal":"joined2_","numVal":10,"derivedProp":"joined2_10"}

Classes and Interfaces​

DerivablesSettings​

DerivablesSettings is a class that extends PropertiesControllerSettings. It provides settings specific to derivable properties.

  • Static Properties:

    • extensionDerivables: A string identifier for this extension, defaulting to 'Derivables'.

  • Constructor:

    • Accepts an optional initial configuration and assigns any provided settings.

DerivablesMetadata​

An interface for metadata associated with derivable properties.

  • from: Specifies the properties from which the derivation occurs.
  • derive: A function that performs the derivation.

DerivablesOptions​

An interface to specify options for derivable properties.

  • derive: A boolean indicating if derivation should take place.

DerivablesExtensionData​

A class implementing TypeToolsExtensionData, it contains:

  • rubric: Object mapping property names to their derivation logic.
  • triggers: Maps property names to lists of dependent properties and guards against repeated derivations.

Derivables​

The core class implementing the derivable properties mechanism, extends functionality via TypeToolsExtension.

  • Static Methods:

    • getExtensionData: Retrieves extension data for a target.
    • typeCheck: Checks if a target has required derivable properties.
    • implementOn: Implements derivable properties on a target.
    • of: Sets up derivable properties according to the rubric provided.

  • Constructor: Initializes with optional settings.

Methods and Functionality​

getExtensionData​

Retrieves extension data related to derivable properties from a given target.

typeCheck​

Validates if a given target can support derivable properties based on its settings.

implementOn​

Adds derivable functionality to a target class, ensuring it can handle property changes and derivations appropriately.

of​

Configures derivable properties on a target using a provided rubric that defines how each property should be derived. It:

  • Checks for circular dependencies with a maximum iteration limit.
  • Initializes derived properties.