CODEWITHSUNDEEP
pythondjangodjango-forms
François Constant
François Constant

Reputation: 5496

How to re-use custom validation in Django?

I need to use the same custom validation in several forms. In other frameworks I would create a new "Validator" class but I'm not sure what's best with Django/Python.

Below is what I did, is there a better way (solution below)?

In any form:

    def clean_image(self):
        image = self.cleaned_data.get("image")

        return validate_image_with_dimensions(
            image,
            expected_width=965,
            expected_height=142
        )

In a validation module

def validate_image_with_dimensions(image, expected_width, expected_height):
    from django.core.files.images import get_image_dimensions

    # the validation code...

    return image

Below is the solution:

In the form:

    image = forms.ImageField(
        max_length=250,
        label=mark_safe('Image<br /><small>(must be 1100 x 316px)</small>'),
        required=True,
        validators=[
            ImageDimensionsValidator(
                expected_width=1100,
                expected_height=316
            )
        ]
    )

In a validation module:

class ImageDimensionsValidator(object):

    def __init__(self, expected_width, expected_height):
        self.expected_width = expected_width
        self.expected_height = expected_height

    def __call__(self, image):
        """
        Validates that the image entered have the good dimensions
        """
        from django.core.files.images import get_image_dimensions

        if not image:
            pass
        else:
            width, height = get_image_dimensions(image)
            if width != self.expected_width or height != self.expected_height:
                raise ValidationError(
                    "The image dimensions are: " + str(width) + "x" + str(height) + ". "
                    "It's supposed to be " + str(self.expected_width) + "x" + str(self.expected_height)
                )

Upvotes: 2

Views: 800

Answers (1)

Pavel Anossov
Pavel Anossov

Reputation: 62918

Form and model fields accept a list of validators:

class YourForm(forms.Form):
   ...
   image = forms.ImageField(validators=[validate_image_with_dimensions])

A validator is a callable object of any kind, feel free to write callable classes (django internal validators are class-based).

For inspiration, look at django.core.validators source.

Upvotes: 2

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