Access Modifiers | Table O Contents

Modifiers that define how an interaction may access the properties and methods of a class are called Access Modifiers in Typescript …

• Access Modifiers | Table O Contents
  • Public O Private
    • Private Lockdown
    • Protected Methods
  • Read Only Properties
  • Last Subtitle
  • Support
    • Patreon

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Public O Private

Hint. By default, all properties of a class and all methods of a class are exposed publicly in Typescript unless otherwise modifed by an Access Modifier in Typescript.

By default, all properties of a Class and all methods of a Class are exposed publicly.

A public exposure in Typescript grants access to all parties in any combination of interactions that are possible to be performed.

Note. The public access feature in Typescript is also available to any external caller unless modified by the programmer.

Private Lockdown

In order to ungrant the default public access in Typescript, all properties and methods of the Class must explicitly be tagged as private with the keyword of private, as follows:

private var y = x.charAt(6);

Note. The keyword of public is also reserved for those moments of coding where the developer wishes to make explicit the already implicit feature of Typescript’s default public access.

Protected Methods

A simple extension of a Class into a child class is not sufficient to award access to private methods of the parent class.

For that, the protected access modifier keyword is essential.

The protected keyword can be placed in front of a parent Class method or property statement, as follows:

protected var y = x.charAt(6);

The protected access modifier through the application of the protected keyword allows permission for a child class to view the properties of its parent class.

In addition, by applying the keyword protected to a method declared in the parent class any child functions may call the methods of the parent Class so tagged, as well.

Read Only Properties

If we take the same parent class property as shown above and assign the readonly keyword to the property statement, then the risk of a mutated value from a collision outside or from inside of the Class from another child or alien class attempting modification of the value is eliminated.

In effect, the readonly keyword creates a modified access to the property that will allow for the view and usage from within the parent Class, but retains immutability from without, as follows:

readonly var y = x.charAt(6);

Note. Access modifier keywords may be combined to produce more robust forms of delegation.

For example, prefixing the private keyword to the readonly keyword creates a variable that can only be viewed from within the parent Class, as follows:

private readonly var y = x.charAt(6);

Last Subtitle

More to come …

Note. The above synopsis was derived from an article written by Blank Author [1].

1. A Narrative of Psychology by Blank Author, Jan #1999

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