guardClass()

guardClass()

Guards the value to be a class of generic type variable Class.

guard-class.func.ts

const guardClass = <
  Class extends Function,
  Payload extends object = object
>(
  value: Class,
  callback?: ResultCallback<Class, Payload>,
  payload?: Payload
): value is Class => isClass(value, callback, payload);

Generic type variables

ClassextendsFunction

A generic type variable Class constrained by Function indicates the captured type of the given value via the return type and the value parameter of the provided callback function ResultCallback type.

Payloadextendsobject=object

The Payload generic type variable constrained by object indicates the type of optional parameter payload of the supplied callback function and payload optional parameter of the guardClass() function from which it captures its value.

Parameters

value: Class

The class of a generic type variable Class to guard.

callback?: ResultCallback<Class, Payload>

The optional callback function of ResultCallback type with parameters, the value that has been checked, the result of this check, and payload of generic type variable Payload with optional properties from the provided payload, to handle them before the result return. By default, it uses resultCallback() function.

payload?: Payload

An optional object of the generic type variable Payload is assigned to the payload of the given callback function.

Return type

value is Class

The return type is a boolean as the result of its statement indicating the value is a generic type variable Class by default of type captured from the supplied value.

Returns

The return value is a boolean indicating whether the provided value is a class of a generic type variable Class.

Example usage

// Example usage.
import { guardClass } from '@angular-package/type';

type PlusFunction = (...param: any) => any;

/**
 * typeof === 'function'
 * instanceof Function === true
 * instanceof Object === true
 */
const FUNCTION: PlusFunction = (x: number, y: string): any => x + y;

/**
 * typeof === 'function'
 * instanceof Class === false
 * instanceof Function === true
 * instanceof Object === true
 */
class Class {

  1030405027 = 'my new number';
  5 = 'my number';

  firstName = 'My name';
  surname = 'Surname';

  x = NUMBER;
  y = STRING;

  get [NUMBER](): number {
    return this.x;
  }
  get [STRING](): string {
    return this.y;
  }

  get [SYMBOL_NUMBER](): number {
    return this.x;
  }

  get [SYMBOL_STRING](): string {
    return this.y;
  }
}

guardClass(FUNCTION); // false
guardClass<Class>(FUNCTION); // type error