Building Relationships

[MUSIC] 0:00 Welcome, I'm Alena. 0:04 In this course we'll be extending from the knowledge learned in a previous course 0:06 to look at additional relationships in the structure on our code. 0:11 Laziness is one of the great virtues of a programmer, 0:15 we don't want to write the same code over and over again. 0:18 This is why one of the core concepts of object oriented programming 0:22 is aimed directly at reducing the amount of repetition that you have to do. 0:26 It's called inheritance. 0:31 At its simplest, it means we can give a child or 0:34 a subclass all the abilities and attributes of a parent or superclass. 0:36 This helps us to greatly reduce the amount of code we need to write. 0:42 Let's take these elephants for example. 0:47 Each of these elephants could be an instance of an elephant class. 0:49 Each object would simply set specific properties such as color and logo. 0:54 Both are created using the same pattern or class. 0:59 But what happens when we want to build a mammoth? 1:03 Not only have we changed the type of material that's used, but 1:07 we've also added tusks. 1:11 Continuing to modify the original pattern to add more features, can get complicated, 1:13 and make it more difficult to create our simple base elephant. 1:19 Then what happens when we want to add additional designs? 1:23 Such as an Elvis elephant. 1:26 Instead, we can keep our original pattern in our class, and 1:29 then extend that class by creating a child, or sub-class, which 1:32 includes all the attributes of the parent, while additionally adding features. 1:37 As another example let's take a bike. 1:43 We have properties such as frame color, number of gears, and current speed. 1:46 We also have methods that control things such as brake, change speed, and 1:51 change gears. 1:55 Now let's say we want to build an electric bike. 1:57 An electric bike is a regular bike with the addition of an electric drive system. 2:00 We would need additional properties for battery and 2:05 motor and a method to control the power such as change_power. 2:08 Instead of adding these properties and methods to the bike class we could create 2:13 a child class named electric bike, that extends the original bike class 2:18 by giving the child access to all the original properties and 2:23 methods while allowing the child to add these additional features. 2:27 In this course, we'll write code to extend a simple directory project. 2:32 If you would like to practice building the original directory, or 2:36 would like a refresher of things that are not covered in this course, 2:40 please check the notes associated with this video. 2:43 Let's take a look at the project. 2:46 The simple directory we'll be starting with has a list of PHP Conferences 2:49 with links to their website, email, and twitter. 2:53 We have the ability to edit and deactivate a listing. 2:56 We also have the ability to add a new listing. 3:03 ll We'be adding premium listings which include a description and 3:05 featured listings which also include a code of conduct. 3:11 These new listing types will be used on the listing page, and also for the forms. 3:15 Along with these features, we'll also add additional styling and navigation. 3:21