Title: QWEB demystification, Part 1 - t-field and t-esc Date: 2016-01-16 11:26 Modified: 2016-01-16 11:26 Category: QWEB Tags: QWEB, safe-eval, openerp, odoo, odoo reports Slug: qweb-1 Authors: Pouya MN Summary: the differences bitween t-field and t-esc, where and how to use? What about other 't's?
When I stated to make some QWEB reports, I was wondering why there are both t-field and t-esc? For example both t-esc="partner_id.name" and t-field="partner_id.name" has the exact same output.
I made a thorough study and I'll tell you the results, but first... Let me write about QWEB, the great html templating engine.
There are some templating language, and some of them are XML-based like Genshi, Thymeleaf or Facelets. But QWEB is exactly designed for Odoo, it has access to the database and python side and context. Other templating engines are more general than QWEB and the can normally access to some kind of context passed in a JSON object only.
The beauty of QWEB is that it is python integrated, there are not just variables but also you can have some python expressions and also it has customizable widgets. I'll write about widgets and using expressions to change the html dynamically.
Appologies me for talking too much, lets get back to the story, t-esc or t-field. The differences are quite a few, in text fields they are just the same but it is not going on like this with the others. The difference is in the interpreter of them and the widgets.t-esc actually calls a safe-eval most of other 't's do the same but t-field can acept only a field name, or a chain of dot seperated related fields. Also, t-field uses form widgets for rendering the selected field while t-esc only returns a simple python output (we can change this and prettify the otherwise blunt t-esc, I'll talk about it in the following parts). For example if you call t-esc on a related field i.e. t-esc="someMany2Onefield" it will print the python __str__ of the class and a record number, just like what you will have if you in python:
print self.someMany2Onefield>>>someMany2Onefield(12,)
but if you use t-field it will display the display_name field or the name_get. The difference is t-field uses form widget of the field as i said before. The same goes with the numerical fields, t-field will use the digits property of the field for decimal point and it will use thousend separator and other settings from the language settings of Odoo, while t-esc simply print the number without formatting (although one can use python's format function in t-esc).
Other 't' tags also use safe_eval, t-set in t-value part, t-if, t-foreach, t-att and t-attf, t-raw and t-log.
qweb_context and of course safe python commands! It raises two questions, what are safe python commands and what is in qweb_context?