<relate> tag

Description

The relate tag is used to define which fields are used when relating two objects.  This tag can be nested in either a hasOne tag or a hasMany tag.  This tag has two argments, from and to.  The from argument specifies the alias of a field on the parent object (the object in which the hasOne or hasMany tag is nested).  The to argument specifies the alias of a filed on the child object.

 

Note: If a field does not have an alias explicitly set using the field tag then the alias defaults to the field's name.

 

Multiple relate tags can be nested under a hasOne or hasMany tag to represent compound relationships such as compound foreign keys made up of more than one field.

 

For detailed information on relationships see the hasOne or hasMany tag documentation.

 

To understand the relate tag consider a SQL join statement.  If you were to join User to Address on an addressId column you would write this SQL code:

 

SELECT *
FROM User as u JOIN Address as a
   ON u.addressId = a.addressId

 
The last line of the query (the one beginning with "on") serves the same purpose as the relate tag.  It says User is related to Address by an addressId column on both objects.  This relationship in XML would look like this:
 

<reactor>
 <objects>
   <object name="user">
     <hasOne name="address">
       <relate from="addressid" to="addressid" />
     </hasOne>
   </object>

   <object name="address" />

 </objects>
</reactor>

Attributes

Attribute

Required

Description

from

yes

 Specifies a field alias on the parent object

to

Yes

Specifies a field alias on the child object

Child tags

None

Example

<reactor>
 <objects>
   <object name="user">
     <hasOne name="address">
       <relate from="addressid" to="addressid" />
     </hasOne>
   </object>

   <object name="address" />

 </objects>
</reactor>