First of all I have tried to research my problem but have not been able to find what I need. My problem might be related to the design of my project (any help would be appreciated).
The problem I am facing is as follows:
I have a few models
I have a model that would be used specifically to create a ModelForm
In this model I have ForeignKey field that is represented by default as a select/option input widget in the ModelForm (for each the value attribute is the ForeignKey and text between the tags is the __str__() of the model the ForeignKey points to. The user sees the __str__() and value attribute of the option tag is submitted which is great).
So far so good but I want to replace the widget with an input text field so I can implement it as a search field.
Now when the user submits the form the string entered in the text input field is submitted and of course django doesn't like that since it expects a foreign key
I already can think of a few solutions to the problem and I am sure I can make it work but each of them feels like I would be violating some best practices. So my question is what should I do?
Do I exclude this particular field from the ModelForm and implement it as an input text field then after form submission make a query with it's value and then store the ForeignKey to the DB
Do I manipulate the data with JavaScript upon submission so that Django receives correct information
Can I clean this fields data with Django and transform it from string to FK?
Am I going the wrong way with this or there is a Django feature for this type of situation?
If anyone has the same problem here is the solution (to my problem at least):
I tried to use the clean_<fieldname> method to change the user entered string to database id. The method wasn't executing because the validation process was stopping earlier because of the difference between the form field and the widget. I redefined the form field to CharField so that step of the validation was working and then the clean_<fieldname> method executes without a problem.
Related
I have a project in which I need to add a custom form field to a form (or formset) in which depending on the choice in the custom field selected, an integer in a database field is changed.
I can't seem to find any examples or prior questions which imply how to modify a database field via a custom field. I suspect it is done by overwriting the save() function in a ModelForm but cannot work out how.
Any advice on solving this problem would be greatly appreciated.
An Example:
My class has an integer field which is the field that needs updating.
class Employee(Model):
years = models.IntegerField()
However this field cannot be updated as it is, instead what is needed is a ChoiceField (I think) with different options that, depending on the selection, changes the field with a +1, -1, or reset to zero.
As previously mentioned this is where I imagine some work with the save() function needs to be done but am unsure.
As a side note in case this affects what can be done, eventually this ModelForm will need to be used in a formset so I can edit multiple objects on one page.
I use "msignup" model for user signups. after signup is complete which works just fine, in the profile of the user I want to let them change some basic information that they used during the signup (which are saved in database in msignup model) using modelform named "accountSettingsForm".
Obviously the original user information must be there in the "accountSettingsForm " and the user would change any piece of information he/she likes.
I know it is possible to set the initial value of the accountSettingsForm:
form = accountSettingsForm(initial={'someFieldName':snomeVariable})
But I assume there is a better way of doing this that I don't know about.
Probably using __init__ methods is more appropriate.
Any helps will be greatly appreciated.
I'm new to Django, and I haven't found the answer yet in the extensive documentation. I'm asking for pointers to research, not for working code. That being said, here's my problem:
In one of my models theres a BooleanField (it gets rendered in the admin form as a checkBox). Let's call it 'A'. It only makes sense to edit other field (say, CharField 'B') if A is checked.
So, is there a way to make B read only, or even changing its content to an empty string, dinamically, if A is checked? Thank you.
(Django 1.5.2, Python 2.7.5)
You're going to need several things to make this work. You may be able to skip some of them depending if you mainly care abut the UI, or the data integrity in the db.
Since the user can (presumably) check/uncheck Field A on the client-side you need some Javascript to enable/disable the appearance of Field B. These docs show how to load custom JS in your ModelAdmin class:
https://docs.djangoproject.com/en/dev/ref/contrib/admin/#modeladmin-asset-definitions
In your ModelForm you may want to do some check in the __init__ method against the value of self.instance.field_a and substitute some kind of ReadOnlyWidget for Field B for the initial display of the form. These docs show how to give your ModelAdmin a custom form class:
https://docs.djangoproject.com/en/dev/ref/contrib/admin/#django.contrib.admin.ModelAdmin.form
If you are writing some Javascript to do that dynamically it make be easier to skip this step and just do it client-side.
Finally you can use Django model validation to ensure that Field B is saved with a null value if Field A is checked:
https://docs.djangoproject.com/en/dev/ref/models/instances/#validating-objects
I'm currently working on a model that has been already built and i need to add some validation managment. (accessing to two fields and checking data, nothing too dramatic)
I was wondering about the exact difference between models and forms at a validation point of view and if i would be able to just make a clean method raising errors as in a formview in a model view ?
for extra knowledge, why are thoses two things separated ?
And finnaly, what would you do ? There are already some methods written for the model and i don't know yet if i would rewrite it to morph it into a form and simply add the clean() method + i don't exactly know how they work.
Oh, and everything is in the admin interface, havn't yet worked a lot on it since i started django not so long ago.
Thanks in advance,
You should use model (field) validation to make sure the returning datatype meets your database's requirements. Usually you won't need this because django's builtin fields do this for you, so unless you've built some custom field or know what you are doing you shouldn't change things.
Form validation is where you clean the user's input, you can add a clean method for every form field by adding a clean_FIELD(self) method, e.g.
class ContactForm(forms.Form):
# Everything as before.
...
def clean_recipients(self):
data = self.cleaned_data['recipients']
if "fred#example.com" not in data:
raise forms.ValidationError("You have forgotten about Fred!")
# Always return the cleaned data, whether you have changed it or
# not.
return data
Before a Form's main clean method is ran, it checks for a field level clean for each of its fields
Generally models represent business entities which may be stored in some persistent storage (usually relational DB). Forms are used to render HTML forms which may retreive data from users.
Django supports creating forms on the basis of models (using ModelForm class). Forms may be used to fetch data which should be saved in persistent storage, but that's not only the case - one may use forms just to get data to be searched in persistent storage or passed to external service, feed some application counters, test web browser engines, render some text on the basis of data entered by user (e.g. "Hello USERNAME"), login user etc.
Calling save() on model instance should guarantee that data will be saved in persistent storage if and only data is valid - that will provide consistent mechanism of validation of data before saving to persistent storage, regardless whether business entity is to be saved after user clicks "Save me" button on web page or in django interactive shell user will execute save() method of model instance.
This is really frustrating,
I can't and can't find how to create a form (I'm guessing a forms.Form form) to update just one field of a more complex model.
The model has 5 fields, and a form to create, update all of them.
But in a different case i need to let the user update only the title (a field in the model), so i need tried so many things until now (including creating an HTML form by hand and from the view to save it, creating a forms.Form and many more, nothing seem to work), There is no code here because i don't even know which one to put....
Maybe some one can help me with that, I'm sure it is a simple thing, But for some reason i am stuck on this for a long time...
Thank you,
Erez
If you're using ModelForms, you just have to define a fields attribute in Meta as a tuple containing just the names of the fields you want. See the documentation.