Grafted fields

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Grafted Fields

Introduction

When there are numerous tables, it is difficult for the user to see get an information that will help one to enter the right data in the right field. So instead of navigating in the relative tables and lose some time, it is more convenient to add a grafted field from that relative table in the table. To be able to sort a column by the content displayed when this content is extracted form a relative table, a grafted field is necessary because the real content is just an id, not the most convenient to sort in human-readable way.

Procedure

Two ways to add a grafted filed

• The first one is to add a __sql__ statement at the beginning of fields.ini, including the grafted field through a join.

__sql__ = "select p.*, d.total from programmation p left join dev d on p.id_programmation=d.id_programmation" 

• The second one is to create the function __sql__ in the delegate class

function __sql__(){
return "select p.*, d.total from programmation p left join dev d on p.id_programmation=d.id_programmation";
}

Sorting order based on relationship

The solution is to hide the field with the id and to add the grafted field with the name in the fields.ini

[name_programmation]
order=10

[id_programmation]
visibility:list=hidden

Debugging

A couple of things to check for:

• 1. If you have set blanket default permissions for your fields using the __field__permissions() method you could be disallowing access to the field.
• 2. If you have set default field visibility in the fields.ini file via the [__global__] section....
• 3. Check to make sure that your __sql__ directive is at the beginning of the file and that it is __sql__ and not _sql_
• 4. Try to enter an obviously invalid SQL query for the __sql__ directive to see if you get an error (to confirm that it is picking up the __sql__ directive at all).

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