Question

What I need:
I want to get object details from DB. I use get() function. The problem I have is, that I make in in a function, and one of the arguments is field name as string:

def delete_file_if_changed(id, change, form, model, field_name='image'):
    if change:
        if field_name in form.changed_data:
            old_image = model.objects.get(pk__exact=id)

Now – how can I do the thing that I can get old_image.field_name – how to do that?

Answer 1

You know, I thought this was your answer at first — it lets you search by a dynamic property: Could the ** operator work?

kw = {field_name:change} # you're not explicit as to which is the field_name
                         # value you would like to search for.
old_image = model.objects.get(**kw)

But, if you already have the object you want, and you just need to get the value of a dynamically named property, then you can use getattr(object, name[, default]):

getattr(old_image, "id", "Spam") # gets old_image.id, if that does not exist, it
                                 # defaults to the str "Spam" Of course, in this 
                                 # context, you probably want 
                                 # getattr(old_image, field_name)