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Validators, whether custom or Django-provided, give us a great way to make sure the content of a field matches a condition we've set.
Did you notice my flip-flop in the video? Writing a custom validator is a great way to have reusable validation, so if I need to do something specific on a lot of fields, I definitely use a custom validator. In the example in this video, though, it just makes more sense to use Django's provided MaxLengthValidator. Sorry if that was a bit confusing!
Django provides us with several validators
already built in, so that we don't have to
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handle things like checking for a maximum
or minimum value, max or min length, or
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a valid email or IP address, but our honey
pot needs to be validated to be blank.
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We're already doing this with
our clean honey pot method,
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but that's not easily reusable, so
we should come up with something else.
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Let's do this two ways.
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The max length validator,
and with a custom validator.
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So we have this easy way of
cleaning our honeypot, and
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this is really good, but
it's not something that is abstracted,
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it's not something that we can apply
to a bunch of different forms.
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We could turn it into that, but
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that's probably more trouble
than it's really worth.
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And we don't wanna have to write
this method every single time
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we use a honeypot.
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We'd probably end up just copying and
pasting it over, and over, and over again.
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That's not the best idea,
so what can we do instead?
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Well, what we can do is we
can bring in a core Django
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feature called validators that
validate data, so let's do that.
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Let's get rid of our clean honeypot.
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And let's come up here, and we want to
do from django.core import validators.
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So that just gives us
all of our validators.
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And here on our honeypot, we want
to specify what the validators are.
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So we can do validators=, and
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we can put in
validators.MaxLengthValidator.
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And the max length is 0.
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Length of zero, if there's any
length at all, then this fails.
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All right so let's come back over here and
we can actually we've already got this set
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up with the bad value, so
let's just hit submit.
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We should see another error
message come out right up here.
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Yep, so here we go hidden field honey
pot ensure this value has at most
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zero characters, it has seven.
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So, great.
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That's actually pretty simple.
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And this actually works really well.
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I like this.
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This is probably how I would
handle this situation.
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Just give it this MaxLengthValidator of 0.
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But sometimes you need something that's
a little more complicated of a validation.
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So let's see how to write
a custom validator.
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So we're just gonna come up here and
we're gonna make a new function.
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And I'm just gonna say must be empty.
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And validators always get a value.
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They get the value that's in
the field that they're validating.
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So we'll just call that value and
we'll say if value.
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If there's anything there at all.
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If there's a value.
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Then we want to raise
forms.validationError.
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And we're gonna say is not empty,
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because really you're reflecting
what the state of the field is.
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So the state of the field is
that the field isn't empty, and
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that field should be empty.
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So then in here,
inside of the MaxLengthValidator,
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we'll just put must_be_empty.
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And then we'll come over here.
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Everything is still filled in.
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And if we submit this,
we should see something new there.
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And there we go,
we have honeypot is not empty.
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So three different ways to handle
cleaning out that one field.
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They all have their own strengths and
weaknesses.
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I'll leave it to you to decide which
one of those solutions is better.
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They both have pros and cons, but
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I tend to like the CustomValidator a bit
better because it's a bit more explicit.
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Anyone applying that to their form
fields will know exactly what it's for.
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