What is the purpose of "Get Instance" in Codeigniter?
How would you explain this to a total beginner?
Ok, so everything in CodeIgniter runs through the super-magic $this variable. This only works for classes, as $this basically defines the current class.
Your controller is a class, so $this is there, allowing you to do $this->load->model('whatever');
In models, you are also using a class. It is slightly different here, as $this only contains useful stuff as you are extending from Model. Still, $this is still valid.
When you are using a helper or a library, you need to find that "instance" or $this equivalent.
$ci =& get_instance();
…makes $ci contain the exact same stuff/code/usefulness as $this, even though you are not in a class, or not in a class that inherits it.
That's an explanation for total beginners after 2 pints, so it's either wrong or about right. ;-)
It's an implementation of the singleton pattern. Essentially, there is only one instance of the class in question, which is designed to be accessible globally. The get_instance method is static and so provides a way of accessing the instance from anywhere in your code.
Related
I have a file named fn.php in my view, then I create a function to post data, like this
function post($input_name){
return $this->input->post($input_name);
}
In my controller I call it like this,
public function myFunc(){
$this->input->load('fn.php');
// then I use the function that I have created like this
post('myinputname');
}
But... I got error, how I can solve this problem? thank you so much
You should take some time to try and understand the MVC architecture. It is, after all, one of the main points of using a framework.
You can't put functions in a view and expect to load them somehow and access them. You can put functions in a model, controller, library or helper. In you case I would suggest a helper:
application/helpers/some_file_helper.php
function post($input_name){
$CI = &get_instance();
return $CI->input->post($input_name);
}
The get_instance() part is only used when $this (CI context) isn't available. This only happens in helpers and libraries. In views, controllers, and models $this is always available.
Model or controller:
$this->load->helper('some_file');
print_r(post('somevar'));
However if all you want to do is access the post variable use $this->input->post('somevar') directly and don't introduce an extra layer.
I am a new to laravel and trying to understand where the view method comes from and what mechanism allows it to be shown in the web.php folder in laravel.
For example :
Route::get('/', function () { return view('welcome'); })
I guess the view function is defined in some class. Bu which class is it and where is that class made reference to in order to access its method?
Thanks a lot if you can help me understanding this!
In most IDEs you can hold CTRL and left-click the function to view it's definition. view() is not defined in a class. It comes from a file called helpers.php.
This file is included at the beginning, so its functions can be used afterwards.
PHP is not only object oriented. Procedural and object oriented programming can be mixed together.
What I do usually in these cases is to search in the whole project (and remember to include vendor directory in your search) for: "function YOUR_FUNCTION_NAME" because somewhere in PHP there must be that function declared, whether is in a class or in a simple .php file.
view() method is a helper method inside src/Illuminate/Foundation/helpers.php. All the methods that declare here will be available everywhere inside Laravel application. You can check view() method here
In a controller class I have this function:
public function index(){
$this->load->helper('url');
$data['title'] = 'News archive';
$this->load->view('news/index', $data);
}
I load helper url because I'm using anchor() in news/index. So seems like it's enough to load helper in the parent function, and I don't have to load it inside news/index.
So my question is what's going on underneath CI that lets me do this? Is load->view a function, or is it pasting the result of executing news/index on $data? How is load->view aware of helper url having been loaded in index? I'm still trying to make sense of how the CI framework works.
Also what would be the best place to load helper, in the constructor, or in each function as we need it?
Also what would be the best place to load helper, in the constructor, or in each function as we need it?
As a rough rule of thumb;
If you use the helper once in a controller - place it in that specific function
If you use the helper in multiple places in a controller - place it in that controllers constructor
If you use the helper in multiple places in multiple controllers - place it in the 'autoload' section once.
you can get all the answer if u go through the Loader Class in codeigniter...
path >> system/core/loader.php
everything that is done is here....
and for ut last question . according to the user guide
http://ellislab.com/codeigniter/user-guide/libraries/loader.html
loader, as the name suggests, is used to load elements. These elements can be libraries (classes) View files, Helpers, Models, or your own files.
so since it just loads the elements...
i usually(prefer) loading it in each function where needed. (unless i need the same elements in other functions too)
There is a helper which I would like to use inside a core class, CI_Router (MY_Router, to be more accurate). In this custom router, I made some modifications to the original code, in order to be able to insert hyphens into my urls.
I have defined the helper on the autoload.php file, as usual, but it seems that I can´t invoque a helper function inside a class other than a view or controller.
Any ideas about how to handle this? My initial approach was to use a helper, so I can reuse it on any place I want.
TYVM.
Helpers are not instantiated until after the core, thus why it does not work.
You will either have to:
Duplicate the function in your MY_Router class, or,
Rethink why you might be using the same function in the Router that you use in a standard controller or view.
Option 1 is obviously easier, but might not be preferable depending on how bad your OCD is.
You could try getting the instance of the main CI object and setting it to a variable, then load the helper using that. Ex:
$ci =& get_instance();
$ci->load->helper('date');
I know that works in other areas, not 100% sure about any of the router classes.
CodeIgniter has a method $this->load->vars($array) that is ideally used in the parent Controller to provide global access to system variables directly in the view. For example:
$this->data['username'] = "john";
$this->load->vars($this->data);
Then in the view, you can easily access john by echoing $username.
My question is, is it possible to use $this->load->vars($array) from within a Model instead of a Controller? This will allow me to abstract away some details from my Controller, making it cleaner. What changes would I have to make to get this working? Would you recommend it; do you think it breaks MVC?
Also, I'm using Datamapper ORM, so my models actually extend the Datamapper object and not the Model object.
Thanks!
Is it possible to use $this->load->vars($array) from within a Model instead of a Controller?
As mentioned, yes you can do this, you can even load a view from a Model, or even run $this->load->vars() in a view and load yet another view.
This will allow me to abstract away some details from my Controller, making it cleaner.
This is like sweeping the dirt under the rug, it didn't go away - it just went somewhere else where you are bound to deal with it later.
Would you recommend it; do you think it breaks MVC?
It's not going to "break" anything, but it implies that maybe your concept of MVC is somewhat broken. If it has nothing do do with the data layer and everything to do with the view layer, it doesn't belong in the Model. There's a good chance there may be some other stuff that doesn't quite belong there as well...
I'm using Datamapper ORM, so my models actually extend the Datamapper object and not the Model object.
You may need to call get_instance() and assign it to a variable or class property for use in DM models, so you can access the Codeigniter object.
Example: $CI =& get_instance(); $CI->load->vars();
Suggestion:
Return the data from the Model in the simplest, most reusable form possible, and then assign it to the view variables in the Controller. If I'm hunting down the source of some variables in a view file, the last place I'd look for them is in the Model. You may end up revisiting this project in the future, so try to be consistent as much as you can, and stick to the suggested, expected practices.