X2Model and Dynamic Fields

Introduction

Typically in Yii, when a model (see: CActiveRecord) is used to retrieve data from a table in the database, the model's attributes are simply inherited from the schema for that table. However, in order to provide the means to add and remove fields from models (and thus from database tables), in addition to providing more advanced options for setting behaviors of attributes, most of the model classes in X2Engine (the ones that are associated with database tables) are extended from a class X2Model. The attributes of all such models are not derived from the database itself but from an attribute registry stored in the x2_fields table. The following columns in the fields table are of particular importance:

Field Name	Typically renders as	Value
modelName	Plain text (filtered/mapped to be human-readable)	The exact name of the model class to which the field belongs, with a few if any exceptions (i.e. fields with modelName="Quotes" belong to class Quote)
fieldName	N/A (attribute label rendered in its place)	The name of the database column
attributeLabel	Plain text	The attribute label (the name of the field as displayed in the UI)
modified	N/A	Whether the field has been modified by the user.
custom	N/A	Whether the field has been created by the user.
type	Plain text (filtered/mapped to be human-readable)	The type of the column. This does not merely specify the canonical MySQL type, but is used for specifying advanced behaviors for the field. See Field Types for more information.
required	Checkbox	Specifies that the model attribute cannot be null or empty, if set to 1.
readOnly	Checkbox	Signifies that the model attribute cannot be modified through user input, if set to 1.
linkType	N/A	In the case that the field is being used as a link, keywords set in this field signify what type of link should be generated in output.
searchable	Checkbox	If set to 1, the field's contents are included in global searches through records.
relevance	Verbatim what it is in the database	A value used for sorting search results: "Low", "Medium" or "High"
isVirtual	N/A	If set to 1, the field does not actually correspond to a database column; rather, it is an ephemeral attribute of the model that is used for passing data from the view to the controller and vice-versa. For instance, it would be used in the case of input that needs to be collected as part of the model (initially) so that it can be put through input validation.

Field Types

The type of a field as set in x2_fields.type, as mentioned before, is not necessarily a canonical MySQL data type, but rather could be a keyword for specifying how the attribute is to be treated and rendered. For example, when rendering an attribute, X2Model and its subclasses use X2Model::renderAttribute(), wherein a case statement is used to distinguish between field types and choose a method of displaying the field.

Type keyword	Canonical type	Description
assignment	VARCHAR	The attribute is rendered as a link using User::getUserLinks. The input field for it is a dropdown list of users and groups.
boolean	TINYINT	Self-explanatory; true or false.
currency	FLOAT	A currency value. Setting a field to this type enables printing currency symbols by values.
date	INT	Date, as a Unix timestamp. Using this type for an integer field ensures it will effectively be treated as a Unix timestamps and converted to a full date when rendered.
dropdown	VARCHAR	Specifies the ID of a list of items stored in x2_dropdowns to use as the permissible values for the field.
email	VARCHAR	Specifies that the contents are formatted like (and correspond to an actual) email address.
int	INT	Self-explanatory
link	VARCHAR	If the field content is an integer, this field specifies another record that it is linked to / associated with (and the model is specified by linkType), and thus the rendered field will be a link to the view of that record. If it is text, it is treated as a URL and simply rendered.
phone	VARCHAR	Field is a phone number and should be treated/formatted as such when formatting for output.
rating	FLOAT	The CStarRating widget should be used to format this field in output.
text	TEXT,VARCHAR	Distinct from VARCHAR in that links within the field's data are automatically transformed using x2base::convertUrls().
url	VARCHAR	Field is a URL
varchar	VARCHAR	Self-explanatory.
visibility	INT	If 1, the record's contents are public. If 0, it is private. If 2, the record is visible only to the user's groups.
percentage	FLOAT	Arbitrary numeric value rendered with a percent symbol after it.
credentials	INT	A record in x2_credentials to use for authenticating with some third-party service. The linkType column represents the service type, and if it contains a colon, then it is the service type (first) and (after the colon) the "system role" alias/nickname for that field (i.e. to identify the field as storing the ID of the SMTP[[wikipedia:Simple Mail Transfer Protocol]]: a network protocol for sending email to a remote server, often involving password authentication and end-to-end SSL encryption. email account for sending notification email).

Setting automatic record links in child classes

Relevant documentation: Component Behavior, CModel::behaviors()

In cases where link and linkType are used, X2LinkableBehavior comes into play; X2Model inherits the behaviors and attributes from that class, since it is attached as a behavior. The method getLink is used for generating controller routes. In this method, it is assumed that the model has the same name as the controller/module. Thus, for every module/controller, the models used by them have the same names, with few exceptions. Thus, this should typically be taken care of already. However, in the case of any new model that is a child class of X2Model, for which the class does not or cannot follow these naming conventions (i.e. a second model inside of a module that needs to use the fields table), the following steps will be necessary:

• Override the behaviors() method so that the subclass does not have X2LinkableBehavior; have it return an empty array or an array with other desired behaviors
• Manually set the following attributes:

  baseRoute

  The route prior to any actions; may contain a module and/or a controller ID.

  viewRoute

  The route (before adding the ID as a GET parameter) used for viewing records.

  autoCompleteSource

  The route that will be used for querying auto-complete results for use in auto-completion fields.

• Create a getLink method in the child class that generates the actual link markup.

(Note: the attributes baseRoute, viewRoute and autoCompleteSource essentially tie the model to a "part" of the web application distinguished by its URL, thus allowing the application to generate URLs for usage of it.)