Create, read, update and delete (CRUD) are the four basic operations of data objects in an application. Because the task of implementing the CRUD operations is so common when developing Web applications, Yii provides some code generation tools under the name of Gii that can automate this process (also known as scaffolding) for us.
Note: Gii has been available since version 1.1.2. Before that, you would have to use the yiic shell tool to achieve the same task.
In the following, we will describe how to use this tool to implement CRUD operations for posts and comments in our blog application.
We first need to install Gii. Open the file /wwwroot/blog/protected/config/main.php
and add the following code:
return array(
......
'import'=>array(
'application.models.*',
'application.components.*',
),
'modules'=>array(
'gii'=>array(
'class'=>'system.gii.GiiModule',
'password'=>'pick up a password here',
),
),
);
The above code installs the a module named gii
, which enables us to access the Gii module by visiting the following URL in browser:
http://www.example.com/blog/index.php?r=gii
We will be prompted to enter a password. Enter the password that we set in /wwwroot/blog/protected/config/main.php
previously, and we should see a page listing all available code generation tools.
Note: The above code should be removed when running on the production machine. Code generation tools should only be used on development machines.
We first need to create a model class for each of our database tables. The model classes will allow us to access the database in an intuitive object-oriented fashion, as we will see later in this tutorial.
Click on the Model Generator
link to start using the model generation tool.
On the Model Generator
page, enter tbl_user
(the user table name) in the Table Name
field, tbl_
in the Table Prefix
field and then press the Preview
button. A preview table will show up. We can click on the link in the table to preview the code to be generated. If everything is ok, we can press the Generate
button to generate the code and save it into a file.
Info: Because the code generator needs to save the generated code into files, it is required that the Web process have the permission to create and modify the corresponding files. For simplicity, we may give the Web process the write permission to the whole
/wwwroot/blog
directory. Note that this is only needed on development machines when usingGii
.
Repeat the same procedure for the rest of the database tables, including tbl_post
, tbl_comment
, tbl_tag
and tbl_lookup
.
Tip: We can also enter an asterisk character
*
in theTable Name
field. This will generate a model class for every database table in a single shot.
At this stage, we will have the following newly created files:
models/User.php
contains the User
class that extends from CActiveRecord and can be used to access the tbl_user
database table;models/Post.php
contains the Post
class that extends from CActiveRecord and can be used to access the tbl_post
database table;models/Tag.php
contains the Tag
class that extends from CActiveRecord and can be used to access the tbl_tag
database table;models/Comment.php
contains the Comment
class that extends from CActiveRecord and can be used to access the tbl_comment
database table;models/Lookup.php
contains the Lookup
class that extends from CActiveRecord and can be used to access the tbl_lookup
database table.After the model classes are created, we can use the Crud Generator
to generate the code implementing the CRUD operations for these models. We will do this for the Post
and Comment
models.
On the Crud Generator
page, enter Post
(the name of the post model class we just created) in the Model Class
field, and then press the Preview
button. We will see a lot more files will be generated. Press the Generate
button to generate them.
Repeat the same procedure for the Comment
model.
Let's take a look at the files generated by the CRUD generator. All the files are generated under /wwwroot/blog/protected
. For convenience, we group them into controller files and view files:
controller files:
controllers/PostController.php
contains the PostController
class which is the controller in charge of all CRUD operations about posts;controllers/CommentController.php
contains the CommentController
class which is the controller in charge of all CRUD operations about comments;view files:
views/post/create.php
is the view file that shows an HTML form to create a new post;views/post/update.php
is the view file that shows an HTML form to update an existing post;views/post/view.php
is the view file that displays the detailed information of a post;views/post/index.php
is the view file that displays a list of posts;views/post/admin.php
is the view file that displays posts in a table with administrative commands.views/post/_form.php
is the partial view file embedded in views/post/create.php
and views/post/update.php
. It displays the HTML form for collecting post information.views/post/_view.php
is the partial view file used by views/post/index.php
. It displays the brief view of a single post.views/post/_search.php
is the partial view file used by views/post/admin.php
. It displays a search form.We can test the features implemented by the code we just generated by accessing the following URLs:
http://www.example.com/blog/index.php?r=post http://www.example.com/blog/index.php?r=comment
Notice that the post and comment features implemented by the generated code are completely independent of each other. Also, when creating a new post or comment, we are required to enter information, such as author_id
and create_time
, which in real application should be set by the program. Don't worry. We will fix these problems in the next milestones. For now, we should be fairly satisfied as this prototype already contains most features that we need to implement for the blog application.
In order to understand better how the above files are used, we show in the following the workflow that occurs in the blog application when displaying a list of posts:
http://www.example.com/blog/index.php?r=post
;PostController
and executes it;PostController
instance executes the index
action by calling its actionIndex()
method. Note that index
is the default action if the user does not specify an action to execute in the URL;actionIndex()
method queries database to bring back the list of recent posts;actionIndex()
method renders the index
view with the post data.
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