I have looked online for the meaning of parent::init(); . All I was able to find was that init() is to initialize some settings which want to be present every time the application runs.
Can anyone please explain the meaning of parent::init() in exact sense, like significance of both the words?
Thanks in advance.( I am sorry if its too simple! )
When we use parent::init(), we are just calling the parent method (in this case init()) inside a method of the current class.
About parent::
For example, let's say we have a class called MyClass. This class have a awesome method that runs alot of things:
class MyClass
{
public function runStuffs()
{
// trigger events, configure external stuff, adding default values to properties.
}
}
Now, after some time, we decided to create a new Class that extends from the first one. And we called MySecondClass:
class MySecondClass extends MyClass
{
}
It already have the method runStuffs(), but, for this second class, we need to do more things in this method, but maintaining what it have.
Sure we could rewrite the whole method and just copy and paste what we have in MyClass and add the new content. But this isn't elegant or even a good practice. what if later on We change the method in MyClass, you probably would like that MysecondClass have that changes too.
So, to solve that problem, we can call the parent method before write your new content:
class MySecondClass extends MyClass
{
public function runStuffs()
{
parent::runStuffs();
// do more things!
}
}
Now MySecondClass->runStuffs() will always do what its parent do and, after that, more stuff.
About the init() method.
init() is a method used in almost all classes from Yii2 framework (since most of then extends from yii\base\Object at some point) and works just like the __constructor() method (native from PHP). But there is some differences, you can read more here.
Actually the init() method is called inside the __constructor(), and the framework encorage us to use init() instead of __construct() whenever is possible.
Now if both are pretty much the same thing, why do they create this method? There is an answer for that here. (take a look at qiang's answer, from the dev team):
One of the reasons for init() is about life cycles of an object (or a component to be exact).
With an init() method, it is possible to configure an object after it is instantiated while before fully initialized. For example, an application component could be configured using app config. If you override its init() method, you will be sure that the configuration is applied and you can safely to check if everything is ready. Similar thing happens to a widget and other configurable components.
Even if init() is called within constructor rather than by another object, it has meaning. For example, in CApplication, there are preInit() and init(). They set up the life cycles of an application and may be overridden so that the customization only occurs at expected life cycles.
Conclusion
So, when you use a init() method and calls parent::init() you are just saying you want to add more things to that method without removing what it already was doing.
The parent::init(); Method is useful to execute a code before every controller and action,
With an init() method, it is possible to configure an object after it is instantiated while before fully initialized.
For example, an application component could be configured using app config.
If you override its init() method, you will be sure that the configuration is applied and you can safely to check if everything is ready.
Similar thing happens to a widget and other configurable components.
In Yii, init() method means that an object is already fully configured and some additional initialization work should be done in this method.
For More Information check this link :
https://stackoverflow.com/questions/27180059/execute-my-code-before-any-action-of-any-controller
Execute my code before any action of any controller
might be helpful to you.
Related
I'm new to Yii2 and returning to PHP dev after a very long time. I have an extensive background in Java development. I stumbled onto this recommendation in the docs for ActiveRecord:
__construct() public method
Defined in: yii\base\BaseObject::__construct()
Constructor.
The default implementation does two things:
Initializes the object with the given configuration $config.
Call init().
If this method is overridden in a child class, it is recommended that
the last parameter of the constructor is a configuration array, like
$config here.
call the parent implementation at the end of the
constructor.
My question is about the last sentence:
call the parent implementation at the end of the constructor.
As a Java dev, this advice seems very weird to me. In Java, not only is it recommended to call the parent constructor as the very first call from your overridden constructor, this is even enforced and it's actually impossible to do it any other way. Either your parent constructor is called first implicitly, or, if you make an explicit call, it MUST be the very first statement in your method. This is enforced by the compiler.
Theoretically, this makes a lot of sense to me. Because as long as you did not call the parent constructor, your parent class did not have the chance to initialize, so any code you write in the constructor before calling the parent constructor would be working with a half-initialized object.
Looking at some SO answers I found, they seem to be going against the advice in the official docs and call the parent::__construct before their own custom logic, as I would expect it. For example, the accepted answer in the question How can I create a constructor in a Yii2 model shows an example where they call the parent first:
function __construct()
{
parent::__construct();
...
}
Another answer in that same question that does follow the official docs' advice scores 0 points:
public function __construct($config = []) {
// your init code here
// ...
parent::__construct();
}
Looking at the article about calling the parent constructor on phptutorial.net, they show an example where they call the parent first, as I would expect it:
class SavingAccount extends BankAccount
{
private $interestRate;
public function __construct($balance, $interestRate)
{
parent::__construct($balance);
$this->interestRate = $interestRate;
}
// ...
}
As I said my PHP is quitte rusty and I am a Yii2 n00b, so I was hoping to get some clarification here about this quitte fundamental thing that is still not clear to me after reading docs, tutorials and SO posts for a few hours now. This investigation was triggered by seeing the constructor being called both first and last very inconsistently in the codebase that I inherited and am currently working on.
In PHP, is there an official recommendation for when to call the parent constructor?
Is the advice to call the parent constructor last also in other PHP frameworks?
Hoping not to incite opinion-based discussion, so please quote official references, point to official docs of other projects etc.
#michal-hynčica correctly stated the reason for your ambiguity(Worthy of votUp). But since you mentioned that the official reference, on the same page (BaseObject), this issue is explicitly stated: line
In order to ensure the above life cycles, if a child class of BaseObject needs to override the constructor,
....
of the constructor, and the parent implementation should be called at the end of the constructor.
According to the description of this link (similar to your question):
init () is called which further calls bootstrap () to run bootstrapping components.
As a result, this is done to ensure configuration.
The same process is done in the controller class and the main module.
Of course, there are many examples like this on the php site (depending on the need)
Also read lifecycles and entry script in yii. components and structure-applications. Good luck
I'm working on a WordPress project. There is a child theme implemented, and the parent one has a class to show authors' links. We have implemented a feature to support multiple authors per post, then we have our own methods for showing the proper links (not a single-author link, but many links joined depending on the authors count).
The complete scenario:
Theme: Newspaper
File: td_module.php (includes/wp_booster/td_module.php)
Class: td_module (abstract, many other classes in the parent theme inherit this one)
Method: get_author()
There are many other classes inheriting td_module in the parent theme, hence I cannot just extend td_module in my child theme since every change to the parent theme would be lost when the theme gets updated
Somehow I need to expand this method to show something different, but I don't want to change the method in the td_module class: even when it would be the fastest / most secure solution, this code would be overwritten on every theme upgrade.
This method is widely used in the Theme, that's why is that important to add some code here.
Why I still have some hope: There is a WP filter td_wp_booster_module_constructor, being called on the constructor of td_module class. The problem is that this class doesn't have any other filter on the method for showing the authors, but just the td_wp_booster_module_constructor filter call on the constructor.
The base PHP (and OOP) question: is it possible to expand / replace a method by using this filter in the constructor somehow?
Some code to clarify:
abstract class td_module {
...
function __construct($post, $module_atts = array()) {
...
// Can I change the get_author behavior by using this filter?
apply_filters("td_wp_booster_module_constructor", $this, $post);
// This is the only filter available in the entire class!
...
}
...
function get_author() {
$buffy = '';
// Code for generating author link ($buffy .= ...)
...
// This function doesn't have any apply_filter, there are no filters available
return $buffy;
}
}
Basically, you can't modify a class definition at runtime. The fact that you have a filter available on the constructor is a red herring and really not relevant.
Either the get_author() has some facility to change it's behaviour from outside class definition (in Wordpress parlance, filter and action hooks), or you simply cannot do it.
Outside of Wordpress, in an application with a proper dependency inversion container, you should probably do this by decorating the class and having all class consumer use the decorated class.
But since you have no way of telling class consumers to use one or the other, and a lot of code out of your control is presumably instantiating the class directly, something like this simply won't fly.
There is one extension, Runkit, that allows for changes of behaviour and definitions at runtime. there is even a method to modify a method definition. although I have not tried the extension, and do not know if it runs in an updated PHP runtime.
Note it is almost certainly a very bad idea to do this on production code, and that since you are dealing with code out of your control anyway you can't even be sure you would be changing the definition before it's used for the first time.
I've also found a repo for Runkit that says that it almost works on PHP 7, if you are absolutely convinced on going that way.
Your issue is that the base class is vendor code which you did not write.
So create a class in between your classes extending it!
Job done!
<?php
class SomeWordpressCrap
{
public function doSomething()
{
return 'something';
}
}
class YourAwesomeNewClass extends SomeWordpressCrap
{
public function doSomething()
{
return 'something better!';
}
}
class OneOfYourExistingClasses extends YourAwesomeNewClass
{
}
UPDATE So it turns out the OneOfYourExistingClasses is also vendor code, so the above solution will not work.
However! You could use Roave's "Better Reflection" lib, which you can find here https://github.com/Roave/BetterReflection
This will allow you to "Change the body of a function or method to do something different", which I believe is exactly what you need. Good luck!
I'm very new to codeigniter ,
I wanted to know what is the meaning of a constructor in a controller . I saw the following code in a codeigniter tutorial -
class upload extends CI_Controller {
function __construct() {
parent::__construct();
$this->load->helper(form);
}
// rest of the class...
My question is when is the constructor invoked - is it called every time the controller serves a request (e.g the controller class is instantiated for each request it receives?)
Well, that's a more general PHP question. Anyway, yes, the magic method __construct() is called (automatically) upon each instantiation of the class, as you can see in the manual: http://www.php.net/manual/en/language.oop5.decon.php
Usually, in CI is not necessary to call a constructor, unless you actually want one. In the example you posted, the code loads the helper on every instantiation of the class - which is the same as loading the helper in every method, just saves a lot of typing and ensures it's not forgotten. You can alternatively put the library/helper/model you want to have alywas loaded in the respective autoload array in config/autoload.php (check "autoloading" in CI's manual)
Once you define a constructor in your child Controller you're compelled to call the parent constructor (of the mail CI_Controller class), because there is where the main CI object is created and all the classes are loaded, and you need those in your child controller too; if fail to do so your child class will construct separately and won't inherit.
I hope I made myself clear, english is not my mothertongue :)
the constructor is magic Literally its called a magic method.
what makes the constructor cool is that it will do things for you BEFORE any of the methods. So if you have an admin class, and someone should be logged in in order to access it - you can check for login in the constructor and bounce them out if they are not authorized.
in the constructor you can load the models, libraries, helpers, etc that your class needs, and they will be available for any method in the class.
you can load in variables that are used by methods. this is really useful for models.
Don't use _construct() function in latest apache & codeigniter
Use helperlin in index() function
That's a general question. Constructor is a function that is automatically called when instantiated. this function helps us to intialize the things that we are going to need frequently in our code like when we have to load the models of helpers like form e.t.c.
$this->load->model('Model_name');
now when you write this line in your constructor you don't need to load this model again and again in your methods of that class.
I am new to PHP and I have a few questions that follows:
Do I need the init function or can I do the job (whatever I need to do in my code) without the init function?
I am saying this because the NetBeans "kinda" created/added automatically the init() function in my project.
In my code I am suppose to create the CRUD functionality in it.
If I don't use it what's the problems I might have and the downsides?
As the official docs would say:
The init() method is primarily intended for extending the constructor. Typically, your constructor should simply set object state, and not perform much logic. This might include initializing resources used in the controller (such as models, configuration objects, etc.), or assigning values retrieved from the front controller, bootstrap, or a registry.
You can have controllers that don't override the init() method, but it will be called under the sheets anyways.
If you are new to PHP, do not start by using a framework. Instead you should learn the language itself.
There is nothing significant about init() function. It is not a requirement for classes in PHP. Hell .. even __construct() is not mandatory in PHP.
That said, Zend Framework executes it right after the controller is created. It is required if you are using ZF.
You can read more about it here.
init() in Zend_Framework for most practical purposes is where you would put code that you need to affect all of the actions in that controller.(at least to test against all of the actions).
For example I often use the init() method to set up the the flashmessenger helper and to set the session namespace I want to be used.:
public function init() {
if ($this->_helper->FlashMessenger->hasMessages()) {
$this->view->messages = $this->_helper->FlashMessenger->getMessages();
}
//set the session namespace to property for easier access
$this->_session = new Zend_Session_Namespace('location');
}
Also Netbeans did not make this method or the controller, Zend_Tool made the controller and the methods utilizing the interface that Netbeans provided. That's why in your PHP settings for Netbeans you have to provide the path to the ZF.bat file and click the register provider button if you change your ZF install.
One more thing...Be aware that there more methods available to the controller that provide hooks into different parts of the dispatch cycle. You may not need them very often but you need to know they are there.
Simply its a constructor for that class(controller)...
init(){
$this->a = 1; //If we set something like this in the init
}
public function fooAction(){
echo $this->a; //1
}
public function barAction(){
echo $this->a; //1
}
ie the variables,objects..that is initialised in init will be available to all the actions in that controller
In my Zend framework project I want to check whether a cookie is set. If it is the case I want to use the cookie contents to login a user.
Since it is neccessary for me to do this automatic login before any controller is called I tried to put it in the Bootstrap. There I want to check the database if the user information is valid. Unfortunately at this point the default database adapter is not yet initialized.
So my question is the following: Where do I put those stuff that should be executed before any controller is called and after all initializing/bootstrapping stuff is done?
I'have not a great experience with Zend Framework but I think you should create a custom generic controller for example GenericController that extends the Zend_Controller_Action and put your code in the preDispatch() function. All your controllers will then a subclass of your custom controller, for example:
class GenericController extends Zend_Controller_Action{
function preDispatch(){
parent::preDispatch();
// put your code here
}
}
class FooController extends GenericController{
...
}
Use the methods:
init()
// and
preDispatch()
implement them in your class, init runs at creation, predispatch runs right before your action method iirc
api
On that page I linked above it states
Note: Usage of init() vs. preDispatch()
In the previous section, we introduced the init() method, and in this section, the preDispatch() method. What is the difference between them, and what actions would you take in each?
The init() method is primarily intended for extending the constructor. Typically, your constructor should simply set object state, and not perform much logic. This might include initializing resources used in the controller (such as models, configuration objects, etc.), or assigning values retrieved from the front controller, bootstrap, or a registry.
The preDispatch() method can also be used to set object or environmental (e.g., view, action helper, etc.) state, but its primary purpose is to make decisions about whether or not the requested action should be dispatched. If not, you should then _forward() to another action, or throw an exception.
Note: _forward() actually will not work correctly when executed from init(), which is a formalization of the intentions of the two methods.