Why does my Django query from Postgres database return the query set in reverse order-CodePudding

I have a model called "Step" that is connected to a learning guide through a foreign key. In my views.py file I am simply querying the steps using this learning_guides_steps = learning_guide.step_set.all() and in the templates I am just looping through the steps using a for loop and displaying the title of the steps like this

        {%for step in learning_guides_steps%}
            <div >
              <!-- Displaying the title of the step with an angle down button beside the title -->
                <div class = "btn-group step" >
                   <a href = "#" class = "btn stepname" role = "button" style = "font-size: 18px;"> {{forloop.counter}}. {{step.title}}</a>
                </div>
            </div>

However when I display it in website its printing in reversed order. Can anyone explain why this is happening and how I can fix this? I am new to Django and Postgres, so any help would be appreciate it. Thank you. My Step model and the views is given below


      class Step(models.Model):
         title = models.CharField(max_length=200, null=False)
         step_description = models.TextField(max_length=1000, null=False)
         # enforces one-to-many relationship between LearningGuide and Step. 
         # Deleting a LearningGuide deletes all the associated steps (CASCADE delete)
         learning_guide = models.ForeignKey(LearningGuide, on_delete=models.CASCADE)
        

class LearningGuide(models.Model):
    title = models.CharField(null=False, max_length=50)
    image = models.ImageField(upload_to='learning_guides_images/')
    short_description = models.TextField(max_length=100, null=False)

    category = models.ForeignKey(Category, on_delete=models.DO_NOTHING)

    indicators = models.ManyToManyField(Indicator, blank=True)

    external_resource = models.BooleanField(default=False, blank=True)
    external_resource_link = models.URLField(null=True, blank=True)

My views.py file:


            learning_guide = LearningGuide.objects.get(pk=learning_guide_id)
            learning_guides_indicators = learning_guide.indicators.all()
            indicators = Indicator.objects.all()

            learning_guides_steps = learning_guide.step_set.all()
            context = {
                'learning_guide': learning_guide,
                'indicators': indicators,
                'learning_guides_indicators':learning_guides_indicators,
                'learning_guides_steps':learning_guides_steps,
                'homepage':False
            }

CodePudding user response：

Option 1 (probably the easiest)
Order the queryresults in your view by using order_by:

learning_guides_steps = learning_guide.step_set.all().order_by('step__title')
# OR to order in the opposite direction,
learning_guides_steps = learning_guide.step_set.all().order_by('-step__title')

Note that I'm guessing you want to order by the title of the step, but you can order by any other field by just replacing title in the order_by, like order_by('step__pk') if you want to order by the step's primary key. Note that the - in each case reverses the direction. And note the double underscore between step and title step__title because you are ordering by a ForeignKey.

Option 2 Set the default ordering on the model itself by using the class Meta:

class Step(models.Model):
    title = models.CharField(max_length=200, null=False)
    step_description = models.TextField(max_length=1000, null=False)
    learning_guide = models.ForeignKey(LearningGuide, on_delete=models.CASCADE)

    class Meta:
        ordering = ['title']
        # OR in the other direction
        ordering = ['-title']

This will require you to run python manage.py makemigrations and python manage.py migrate

Option 3
Add an order field to the step, and order by that. This way you can set the order, and not order alphabetically, or by an auto generated primary key:

class Step(models.Model):
    title = models.CharField(max_length=200, null=False)
    order = models.PositiveIntegerField(default=1)
    step_description = models.TextField(max_length=1000, null=False)
    learning_guide = models.ForeignKey(LearningGuide, on_delete=models.CASCADE)

    class Meta:
        ordering = ['order']
        ordering = ['-order']

Note that this third option will also require you to run python manage.py makemigrations and python manage.py migrate. I've added the default value of 1 to the order so that this migration will not complain about a NULL value, but it means that ALL the Steps will have an order of 1 until you change it. There is a way around this, but I think this will work.