20110714

Insert Window has wrong title

Ein Bug, der mit den subtilen Änderungen für die Listings gekommen ist: das Insert-Fenster zeigt nicht mehr “Einfügen nach <Listentitel>”, sondern nur noch “<Listentitel>”.

Kleine Ursache mit großer Wirkung: ich habe gemerkt, dass ich meine Konzept von “format” und “action” noch überdenken muss. Da funktionierte einiges bisher lediglich zufällig.

Ich habe bei der Gelegenheit auch nochmal einen Blick auf django-piston geworfen. Darauf umzustellen wäre sicherlich sinnvoll, aber auch einiges an Arbeit.

Okay, also wir haben zwei große Kategorien von URI-Handler api_list_view und api_element_view. Momentan ist es ziemlich undurchsichtig, in welchem Datenformat Lino auf Anfragen antwortet.

The methods POST, PUT and DELETE always return JSON (an object with properties message, result, alert,…)

But for GET requests it is currently quite subtle:

view	fmt	response
list	grid*	HTML (with onReady that will open the GridWindow)
list	json	JSON (an object returning the data rows and some meta info like the title)
list	insert	HTML (with onReady that will open the InsertWindow with a data_record)
list	listing	HTML (with onReady that will open the InsertWindow in Listing mode)
elem	detail*	HTML (with onReady that will open the DetailWindow with a data_record)
elem	json	JSON (an object returning the detailed data row and some meta info like the title, navigator info,…))
elem	insert	JSON (an object returning the detailed data row and meta info like the title))

An internal but important change: there’s a new URI parameter an (action name, e.g. detail, grid, insert), and fmt is used to explicitely specify the expected data format (html, json, csv).

Virtual fields on abstract models don’t work

There are currently still two types of virtual fields in Lino: - (old) defined as model methods with an attribute return_type - (new) defined as a “real” lino.fields.VirtualField

The old type uses the magic attribut _return_type_for_method. As I discovered today, this trick fails when it is used on an abstract model that has more than one subclasses. Listing is was such a case (preview). It worked as long as there was only one subclass of Listing (lino.apps.dsbe.ContractsSituation), but now that there is a second one (lino.models.DataControlListing), it uses the same field instance for both classes, leading to a clash “<lino.fields.DisplayField instance at 0x02008670> has already an attribute ‘_return_type_for_method’”

Solution was to use a real VirtualField instead of a model method with an attribute return_type.

Old method:

def preview(self,request):
    return self.header() + self.body() + self.footer()
preview.return_type = fields.HtmlBox(_("Preview"))

New method:

def get_preview(self,request):
    return self.header() + self.body() + self.footer()
preview = fields.VirtualField(fields.HtmlBox(_("Preview")),get_preview)

This is the second use case of lino.fields.VirtualField (the first being lino.utils.mti.EnableChild), so after this change I discovered and fixed a few bugs.

Checkin 20110714