Django TypeError: 'RelatedManager' object is not iterable

Question

I have these Django models:

class Group(models.Model):
    name = models.CharField(max_length=100)
    parent_group = models.ManyToManyField("self", blank=True)
    
    def __unicode__(self):
        return self.name


class Block(models.Model):
    
    name = models.CharField(max_length=100)
    app = models.CharField(max_length=100)
    group = models.ForeignKey(Group)

    def __unicode__(self):
        return self.name

Lets say that block b1 has the g1 group. By it's name I want to get all blocks from group g1. I wrote this recursive function:

def get_blocks(group):
    
    def get_needed_blocks(group):
        for block in group.block_set:
            blocks.append(block)

        if group.parent_group is not None:
            get_needed_blocks(group.parent_group)

    blocks = []
    get_needed_blocks(group)
    return blocks
    

But b1.group.block_set returns a RelatedManager object, which is not iterable.

What am I doing wrong and how can I fix it?

Coterie

Answer 1

Try this:

block in group.block_set.all()

Moncear

Does anyone know why RelatedManager is not made to be iterable? I would have expected it to be that way... – Redware

This comment is a little late, but the reasoning is that you can use the filtering methods on the manager in order to restrict the query before performing a fetch to the db. – Funky

@stalepretzel, because it works exactly as a standard django manager. You don't call Model.objects and iterate over it. You call Model.objects.all() and then you iterate. Django manager =/= Django queryset. – Javelin

and if you are using it in a template for loop you can do {% for object in objects.other_object_set.all %} – Hard

@Redware ...especially since it's called a "blocks_SET" - and not a "blocks_relatedmanager". Or "blocks_set_relatedmanager". – Humfrey

Answer 2

Use it like a Manager. If you want all the objects then call the all() method.

Nape

Answer 3

you have to use .all() with related name or childModel_set model name .

in views.py use :

for item in object.relatedname.all():
    do something ......

in html templates use:

 {% for item in object.relatedname.all %}
   do something ......
 {% endfor %}

Syncopated

Thank you for your response, but could you explain why this is the mechanism and how it works? I am just a bit confused that what makes difference between having those paranthesis and not having them. Thank you. – Doughman

Answer 4

If you are expiriencing this error in Django template try:

{% for block in group.block_set.all %}
{{ block }}
{% endfor %}

Blythebm