Collection classes in php

A Collection class is an OOP replacement for the traditional array data structure. Php classes chicago Much like an array, a collection contains member elements, although these tend to be objects rather than simpler types such as strings and integers.

Applications frequently have objects that contain a group of other objects, and this is a great place to make use of collections.

Php classes online For example, suppose we decide to create a book store system. Php classes in pune kothrud Let’s say we’ve written a customer class which, among other things, holds a list of books that the customer would like to purchase:

Additionally, to make sure the array is available for any code that might access it, we must populate the list of information from the database at the same time as the customer information. Free online php training video This means that even if we want to print just the customer’s name, we must fetch all of the item information, unnecessarily increasing load on the database and potentially bogging down the entire application.

We can solve those problems by creating a collection class as an OOP wrapper around the array and use lazy instantiation. How to use php classes Lazy instantiation is the mechanism by which we create elements in the array only when we actually need it. Online php programming classes It’s called “lazy” because the object determines on its own when to instantiate the component objects rather that blindly creating them when it is instantiated. Online classes for php A Basic Collection Class

A collection class needs to expose methods that allow us to add, retrieve, and delete items, and it’s helpful to have a method that lets us know the size of the collection. Php classes and objects examples So, a basic class would start like this:

The $items array provides a location in which to store the objects that are members of the collection. Php training classes addItem() lets us add a new object to the collection, deleteItem() removes an object, and getItem() returns an object.

With addItem(), we add an object to the collection by putting it in the $items array at a specified location specified by $key (if no key is provided, we let PHP pick the next available index). Online php training videos If an attempt is made to add an object using a key that already exists, an exception should be thrown to prevent inadvertently overwriting existing information: public function addItem($obj, $key = null) {

The deleteItem() and getItem() methods take the key as a parameter indicating which items are targeted for removal or retrieval. Php les classes An exception should be thrown if an invalid key is supplied. Php online training from india public function deleteItem($key) {

Because the $key parameter to the addItem() method is optional, we won’t necessarily know the key used for each item in the collection. Classes in php tutorial pdf Adding a method that can provide a list of keys to any external code that might need it is a good idea. Php built in classes The keys can be returned as an array: public function keys() {

And because getItem() and deleteItem() can throw an exception if an invalid key is passed, a means of determining whether a given key exists in the collection is also a good idea. Php classes in karachi public function keyExists($key) {

To use the Collection class as it stands now, create the file Collection.php and save the code for the Collection class in it. Php list classes Create files for the KeyInvalidException and KeyhasUseException classes, too (they can be simple sub-classes of the base Exception class). Php classes in pune Be sure to add require statements if you’re not using an autoloader, and then try the following test code:

Collections can be seen as more-specialized way of working with lists for which certain contracts are guaranteed. Php classes in jaipur A Collection class is a very useful OO alternative to the traditional array, and one that can be implemented in virtually any application you might build. Php classes in urdu It provides careful management of its members and a consistent API that makes it easy to write code that uses the class.

Guys, I don’t mean to be a pain or something, but really, what is the real benefit of this implementation based on Object Oriented Design ? We should pay attention to the language itself, which had major improvements with the advent of SPL and aforementioned classes such as ArrayObject, or interfaces such as ArrayAccess. Php classes and objects We should help the community with articles that really make developers think about how to make the code they write better and better. Php classes in ahmedabad How about writing articles on Test Driven Development, or tools that help build software using this approach, such as Mockery, Hamcrest or Codeception ? Despite some very good articles on OOD, mainly written by Alejandro Gervasio here, it’s all about re-implementing things that other (many) experienced developers already have implemented in the language itself ! We should help the community with much more than that.

I have put this type of class into practice many times and have found it useful. Php classes in borivali The Collection class is a good place to put universal functionality that is independant of the object being stored, like sorting by named properties, min, max, etc.. Les classes en php There may be existing api calls that come close to what’s needed, but eventually you’ll need to go beyond the basics provided.

The one problem I see with the demo is that submitting an object to the dictionary without a key value will cause the Collection container to store an object that is not retrievable. Php classes bhopal Better to force the use of a key, explicity provided or generated by some method in the Collection class.

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