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Podcast: iteration
Episode:

Encapsulation
Category: Technology
Duration: 00:39:54
Publish Date: 2019-06-24 04:00:23
Description:

Episode 6 - More Code Examples

  • Drawing from Chapter 7 - Encapsulation

A weekly podcast about programming, development, and design through the lens of amazing books, chapter-by-chapter.

Encapsulate Record (162)

var organization = { name: "JP Sio", country: "USA" };

becomes ⬇️

class Organization {
  constructor(data) {
    this._name = data.name;
    this._country = data.country;
  }

  get name() {
    return this._name;
  }
  set name(arg) {
    this._name = arg;
  }

  get country() {
    return this._country;
  }
  set country(arg) {
    this._country = arg;
  }
}
  • you can hide what is stored and provide methods
  • consumer of class Organization doesn't need to know / care which is stored and which is calculated
  • nice getter and setter methods
  • makes it easier to refactor -> can hide implementation of internals and update the internals while keeping the same external interface

Encapsulate Collection (170)

class Person {
  get courses() {
    return this._courses;
  }
  set courses(aList) {
    this._courses = aList;
  }
}

becomes ⬇️

class Person {
  get courses() {
    return this._courses.slice();
  }
  addCourse(aCourse) {
    /*...*/
  }
}
  • slice() is key here, does not modify the original array - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/slice
  • common approach is to provide a getting method for the collection to return a copy
  • basically, never mutate the original

Replace Primative with Object (174)

orders.filter(0 => "high" === o.priority || "rush" === o.priority)

becomes ⬇️

orders.filter(o => o.priority.higherThan(new Priority("normal")));
  • this goes back to "Primitive Obsession"
  • programmers are often hesitant to create their own types and rely only on primitives. i.e. representing a phone number as a string instead of as it's own type

A telephone number may be represented as a string for a while, but later it will need special behavior for formatting, extracting the area code, and the like

  • create a new class for that bit of data
  • at first, the class does very little. in fact it probably only wraps a primitive
  • but now you have a place to put behavior specific to its needs

Inline Function (115)

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