Cfrgtkky

So, I have the following in my models.py:

UNITY_CHOICES = (

    ('g', 'Gram(s)'),

    ('kg', 'Kilogram(s)'),

    ('l', 'Liter(s)'),

    ('cl', 'Centiliter(s)'),

)

class Recipe_Ingredient(models.Model):

    recipe = models.ForeignKey(Recipe, on_delete=models.CASCADE)

    ingredient = models.ForeignKey(Ingredient, on_delete=models.CASCADE)

    quantity = models.FloatField()

    cost = models.DecimalField(max_digits=20, decimal_places=2)



    quantityUnit = models.CharField(

        max_length=2,

        choices=UNITY_CHOICES,

        default=GRAM,

    )

class Ingredient(models.Model):

    name = models.CharField(max_length=200)

    articleNumber = models.IntegerField(unique=True)

    costPrice = models.DecimalField(max_digits=20, decimal_places=2)

    costAmout = models.FloatField()

    costUnity = models.CharField(

        max_length=2,

        choices=UNITY_CHOICES,

        default=GRAM,

    )

And I have a simple form to add this model to my database:

class Recipe_IngredientForm(forms.ModelForm):

    class Meta:

        model = Recipe_Ingredient

        fields = ('quantity', 'quantityUnit', 'ingredient')

So I was wondering if there's a way of filtering the quantityUnit available choices depending on the ingredient chosen.
I'll try to make it clear by an example: Let's say I choose to add Potato and the costUnity for Potato is 'g', then I want to make 'kg' and 'g' the only choices for quantityUnit. Is that a good example? I can try to think of something better if it's not clear enough.
Anyway, is it possible to do such thing? Thanks.

UPDATE:
forms.py:

class Recipe_IngredientForm(forms.ModelForm):



    class Meta:

        model = Recipe_Ingredient

        fields = ('quantity', 'quantityUnit', 'ingredient')

template:

{% extends 'recipe/base.html' %}



{% block content %}

    <h1>Add Ingredient to Recipe</h1>

    <form method="POST" class="post-form">{% csrf_token %}

        {{ form.as_p }}

        <button type="submit" class="save btn btn-default">Save</button>

    </form>

{% endblock %}

Rendered HTML:

<h1>Add Ingredient to Recipe</h1>

<form method="POST" class="post-form"><input type="hidden" name="csrfmiddlewaretoken" value="tXVR3NM1R4TBwOJArWWClL71r8S5C18gWKz9mKK42wlEamf6NcBjzrieF5dQBOaO">

    <p>

        <label for="id_quantity">Quantity:</label>

        <input type="number" name="quantity" required="" id="id_quantity" step="any">

    </p>

    <p>

        <label for="id_quantityUnit">QuantityUnit:</label>

        <select name="quantityUnit" id="id_quantityUnit">

            <option value="g" selected="">Gram(s)</option>

            <option value="kg">Kilogram(s)</option>

            <option value="l">Liter(s)</option>

            <option value="cl">Centiliter(s)</option>

        </select>

    </p>

    <p>

        <label for="id_ingredient">Ingredient:</label> <select name="ingredient" required="" id="id_ingredient">

        <option value="" selected="">---------</option>

        <option value="1">Carrot</option>

        <option value="2">Potato</option>

        <option value="3">Water</option>

        <option value="4">Juice</option>



        </select>

    </p>

    <button type="submit" class="save btn btn-default">Save</button>

</form>