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Designing Interfaces in PHP

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Passing Abstract Methods

3:36 with Alena Holligan

By defining another interface method, we'll explore another feature of abstract classes. When a class is defined as abstract, it does not need to define all methods. Instead it passes that requirement to the next NON-abstract class.

Currently, the collection class is abstract and 0:01
it implements the CollectionInterface. 0:05
All methods from the interface are being implemented in the collection class. 0:07
Let's add one more method to that interface. 0:12
We'll call this public function getTitle. 0:15
Now let's preview our site again. 0:22
We get another error like we've seen before because we have not 0:25
implemented our required method. 0:28
But let's take a closer look at that error. 0:30
First, notice that the error is on the post class, not on the collection class. 0:32
The next part of the error explains why. 0:39
The abstract method must either be implemented or 0:42
the class itself may be declared abstract. 0:46
Because the collection class is abstract. 0:50
And therefore cannot be instantiated, 0:52
it is not required to implement all the required methods itself. 0:55
Instead, this requirement is passed to any non-abstract class, 1:00
extending the collection class. 1:05
Let's add this method to the post class. 1:07
Public function getTitle. 1:20
First, if this count is equal to 1, 1:27
This means that we're on a single post page. 1:37
If we're on a single post page, we want to return the current title. 1:41
If we make it past this return, we'll simply return Latest Posts. 1:50
Let's clean up our pages. 1:59
In header.php, in our views folder, We used the title twice. 2:00
Let's replace those with this new method instead, content getTitle. 2:08
Now we can remove the title from the index page. 2:27
Since we don't need to set the title, we can make this a single if statement. 2:43
So, if our content is not set or 2:49
the content count is not equal to 1, or, 2:55
The content current status does not equal published. 3:06
Then we will select all posts. 3:15
Once again, 3:17
let's preview the site to make sure everything is still functioning properly. 3:18
Looks good. 3:27
We're ready to add a second content type for 3:28
pages by extending a second child of the collection class. 3:31