Looking for some implementation ideas here. I am trying to design a custom polling system for my school, to allow teachers to give students polls to take.
I have a Poll model, Question model (with a foreignkey to Poll model), and Choice model (with a foreignkey to the Question model).
What I need to be able to do is allow whoever is adding questions to choose the type of choices that will be shown. For example, one question should be able to be multiple choice (displayed via a radio buttons), and another question should be able to be "Check all that apply."
What is the best way to allow the creator of the poll to determine how the choices are shown? Should I do a CharField() with choices, and deal with it manually in the view? That doesn't seem efficient.
Use a field in your model that has choices for the different ways people can choose (it doesn't have to be CharField, you could also use a SmallIntegerField and map numbers). Create different form classes for each way of choosing and decide in the view which one to apply based on the value of the "way of choosing"-field. It's a straight-forward way and not that much of a hassle if abstracted nicely.
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I have a ManyToMany relationship between two Django Models: Team and Member. A single Member can be part of multiple teams. I am able to successfully bind a Form class to a CreateView, and, using the standard ModelMultipleChoiceField,can successfully save the Form using the save_m2m method.
However, the default widget for the field is not suitable for my user experience. Instead of using a picklist, I would like to create a separate select box for each number of selectable Members per team. For example, if the Team can have 7 Members, I would like to show 7 select boxes, rather than one pick list that a user selects 7 different objects from.
I understand I may not get a complete answer, but would appreciate any pointers on if I should be looking into overriding the Field with a custom MultiWidget, or if using an inline formset might be a more appropriate route. Or, something else...
At the end of the day, I ultimately decided to stick with a single ModelForm for the Create Team form. Within this ModelForm, I dynamically create the number of fields I will need for the number of Member per team, and have created a function within the form that yields those fields.
I perform validation on those fields within the generic clean method of the ModelForm. I use the yield method within the Template to control displaying the individual fields.
I am sure it is not the most Django-y approach, as many people seem to use inlineformsets in theory, but this worked and the code does not seem overly hacky or unmaintainable.
Recently I've been developing a Django website, which includes the owner being able to add content with descriptions etc.
The problem I'm having is: How can I make the fields support multiple languages? (3 in this case)
The approach I tried was: Creating a model with 3 text fields, have my content model take that model as a foreign key. This sort of works, but now I would have to create all the descriptions first, separately, before creating the actual object it is being used by. This is, in my opinion, a bad idea.
What I would like to be able to do, is to have 3 text fields in the model which is actually using those 3 text fields' admin page, but without actually having 3 text fields in that model.
Using inlines would work, but I'd have to make my multilanguage textfield model have a foreign key to my content model, instead of the other way. This would mean the multilanguage model works for only other model type.
So, to clear the question up:
How can I have a TextField and a CharField support multiple languages?
How can I show the ForeignKey's target model's creation widget in it's owner's admin page?
How can I use inlines, without locking the inline to just one model type?
How can I make a model act like a field?
How can I write a custom TextField?
Answering any of those will be enough for me to solve my problem.
Thanks.
There is too many questions and the docs is at your reach... I'll just answer the easiest one you should have search for by yourself.
How can I have a TextField and a CharField support multiple languages?
You should have a look to i18n here
How can I write a custom TextField?
Have a look to custom Fields
What is the best way to conditionally display a field in the admin depending upon the values of other fields?
In particular I'm thinking about the add_form and change_form. Whenever a certain choice is selected I'd like to hide or disable some fields.
I'm thinking that this might require a javascript solution, but am wondering if there is a better (i.e. builtin) way to do this.
Bernhard is right. You might be able to hack the admin view and template to conditionally show/not show widgets for a field, but if you want to do it dynamically based on user behaviors in the admin, you'll be using javascript.
It's not so terrible, though. At least the Django admin templates have model- and instance-specific ids to give you granular control over your show/hide behavior.
My answer may sound esoteric - but I suspect the design direction you may be taking could benefit from some reconsideration. When an interface requires that much TLC to resort to AJAX to make for a superior UX I am inclined to not use Admin interface for that.
My personal view of the Admin interface of Django is that it is a great freebie that gives me an instant CRUD view at a basic level. I would refrain from piggy backing on it for those who need a more user friendly interface (even if some of these users are handling admin functions). You will acquire technical debt in trying to do these type of Ajax UI/UX and complex form validations using the Admin interface.
I think you should be able to create your own ModelForm and specify that the admin uses that (https://docs.djangoproject.com/en/1.7/ref/contrib/admin/#django.contrib.admin.ModelAdmin.form).
Use the _init__() method of the form to selectively display the fields.
I will give it a try and update this answer if it works.
(Actually re-reading the question, it depends. If "values of other fields" is set before the page is loaded, this idea should work. If you want an instant response - click one field and another appears/disappears, yes you will need JavaScript).
Hi everyone I have a few questions about the django admin.
First the relevant details. I currently have Client, Printer, Cartridge, and Order models.
The Printer model has a ManyToManyField to the Cartridge model, which would allow you to select all the cartridges that can be used with that printer.
The Cliente has a ManyToManyField to the printers which they own.
1) I want to create an Order through the Django admin which lets your specify the Client, a dicount, and multiple cartridges through a ManyToManyField. This is getting kinda tricky because I have to do it through another table that specifies whether it's a new Cartridge or a refill.
2) I want the admin to filters the Cartridges to only show the ones that belong to the printers that they own.
3) Also I would like to have a field that holds the total price of their order, but it should calculate it based on how many cartridges they have added to the order. I don't know if this should be done by adding more of the same cartridge to the order or by having another field in the related table that specifies the quantity.
Can this be done in the admin or do I need to use a form? And if so how would I go about adding this to the admin? It seems difficult and probably something I will have to do in multiple parts since in order to filter the list of cartridges I have to know the client beforehand.
As far as I can see, no, it's not really possible. The development version has some methods for limiting foreign keys, but it doesn't seem to me that limiting based on the customer is possible, since it depends on separate foreign keys.
The best suggestion, if you're really bent on doing it in the admin form, would be to use Javascript to do it. You would still have to make AJAX calls to get lists of what printers customers had and what cartridges to show based on that, but it could be done. You would just specify the JS files to load with the Media class.
But I think that's more work than it's worth. The easiest way I would see to do it would be with Form Wizards. That way, you'd have a step to select the customer so on the next step you know what cartridges to show.
Hope that helps!
I've worked similar problems, and have come to the conclusion that in many cases like this, it's really better to write your own administration interface using forms than it is to try and shoehorn functionality into the admin which is not intended to be there.
As far as 3) goes, it depends on what your product base looks like. If you're likely to have customers ordering 50 identical widgets, you probably do want a quantity field. If customers are more likely to be ordering 2 widgets, one in red, one in blue, add each item separately to the manytomany field and group them in your order interface.
How can I use boolean choices in a model field to enable/disable other fields. If a boolean value is true/false I want it to enable/disable other model fields. Is there a way to natively express these relationships using django models/forms/widgets? I keep writing custom templates to model these relationships, but can't figure out a good way to represent them in django without a special template.
For example:
class PointInTime(models.Model):
is_absolute_time = models.BooleanField()
absolute_time = models.DateTimeField()
is_relative_time = models.BooleanField()
days_before = models.IntegerField()
So if the is_absolute_time is True, I want the absolute_time entry to be editable in the GUI and the days_before entry to be grayed out and not-editable. If the 'is_relative_time' flag is True, I want the absolute_time entry to be grayed out, and the days_before value to be editable. So is_absolute_time and is_relative_time would be radio buttons in the same Group in the GUI and their two corresponding fields would only be editable when their radio button is selected. This is easy to do in a customized template, but is there a way to use a model/form in django to natively show this relationship?
It would be helpful to clarify what you mean by "natively show this relationship," and think clearly about separation of concerns.
If all you want is to "gray out" or disable a certain field based on the value of another field, this is purely a presentation/UI issue, so the template (and/or Javascript) is the appropriate place to handle it.
If you want to validate that the submitted data is internally consistent (i.e. absolute_time is filled in if is_absolute_time is True, etc), that's a form-validation issue. The place for that logic is in the clean() method of your Form or ModelForm object.
If you want to ensure that no PointInTime model can ever be saved to the database without being internally consistent, that's a data-layer concern. The place for that is in a custom save() method on your model object (Django 1.2 will include a more extensive model validation system).
All of those options involve writing imperative code to do what you need with these specific fields. It may be that you're looking for a way to represent the situation declaratively in your model so that the code in all three of the above cases can be written generically instead of specifically. There's no built-in Django way to do this, but you could certainly do something like:
class PointInTime(models.Model):
field_dependencies = {'is_absolute_time': 'absolute_time',
'is_relative_time': 'days_before'}
... fields here ...
Then your model save() code (or your Form clean() code, or your template), could use this dictionary to determine which fields should be enabled/disabled depending on the value of which other one. This generalization is hardly worth the effort, though, unless you anticipate needing to do this same thing in a number of different models.
Lastly, a few schema design alternatives you may want to consider to get your data layer better normalized:
If there are only two valid states (absolute and relative), use a single boolean field instead of two. Then you avoid possible inconsistencies (what does it mean if both booleans are False? Or True?)
Or simplify further by eliminating the booleans entirely and just using Null values in one or the other of absolute_time/days_before.
If there might be more than two valid states, use a single IntegerField or CharField with choices instead of using two boolean fields. Same reason as above, but can accomodate more than two options.
Since a RelativeTime and an AbsoluteTime don't appear to share any data fields with each other, consider splitting them out into separate models entirely. If you have other models that need a ForeignKey to either one or the other, you could model that with inheritance (both RelativeTime and AbsoluteTime inherit from PointInTime, other models have ForeignKeys to PointInTime).
I'm not entirely sure what you're doing with these objects but whichever the user chooses, you're pointing to a single moment in time. "5 days ago" is "Thursday" and vice-versa.
So unless the dates roll with the site (eg the record with "5 days ago" will still mean Thursday, tomorrow, etc), surely this is only an interface problem? If that's the case, I'd stick with a single value for the date in your Model and let the form and view do all the work.
That solves the auto-generated Admin side of things as you'll just have one field to contend with but it won't natively give you the choice between the two unless you write your own form widget and override the ModelAdmin class for your Model.
If this isn't the case, please ignore this answer.