Additional variables (context) on a ModelSerializer?

[George Mamalakis]

Hello everybody,

Is there I way I could process more context on my ModelSerializer other than that of my model? I wish, for example, to pass additional information on listing, that are not stored in the model my Serializer is connected.

Thanx all in advance!

[Denis Cornehl]

Hi George, 

you can override "get_serializer_context" in your view. Then you will be able to access the information inside the serializer by using self.context. 

Alternative is to provide the data in view-methods. The view is in the serializer-context  by default (self.context['view]). 

2014-02-07 George Mamalakis <mam...@gmail.com>:

Hello everybody,

Is there I way I could process more context on my ModelSerializer other than that of my model? I wish, for example, to pass additional information on listing, that are not stored in the model my Serializer is connected.

Thanx all in advance!

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[George Mamalakis]

Hi Denis,

Thank you for your immediate and precise answer! I will try the methods you are proposing to me. Before doing so, is there any documentation on any of your methods that I could read?

On Friday, February 7, 2014 10:55:35 AM UTC+2, Denis Cornehl wrote:

Hi George, 

you can override "get_serializer_context" in your view. Then you will be able to access the information inside the serializer by using self.context. 

Alternative is to provide the data in view-methods. The view is in the serializer-context  by default (self.context['view]). 

2014-02-07 George Mamalakis <mam...@gmail.com>:

Hello everybody,

Is there I way I could process more context on my ModelSerializer other than that of my model? I wish, for example, to pass additional information on listing, that are not stored in the model my Serializer is connected.

Thanx all in advance!

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[Denis Cornehl]

http://www.django-rest-framework.org/api-guide/serializers#including-extra-context

2014-02-07 George Mamalakis <mam...@gmail.com>:

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[George Mamalakis]

Thanx again!

On Friday, February 7, 2014 11:34:59 AM UTC+2, Denis Cornehl wrote:

http://www.django-rest-framework.org/api-guide/serializers#including-extra-context

2014-02-07 George Mamalakis <mam...@gmail.com>:

Hi Denis,

Thank you for your immediate and precise answer! I will try the methods you are proposing to me. Before doing so, is there any documentation on any of your methods that I could read?

On Friday, February 7, 2014 10:55:35 AM UTC+2, Denis Cornehl wrote:

Hi George, 

you can override "get_serializer_context" in your view. Then you will be able to access the information inside the serializer by using self.context. 

Alternative is to provide the data in view-methods. The view is in the serializer-context  by default (self.context['view]). 

2014-02-07 George Mamalakis <mam...@gmail.com>:

Hello everybody,

Is there I way I could process more context on my ModelSerializer other than that of my model? I wish, for example, to pass additional information on listing, that are not stored in the model my Serializer is connected.

Thanx all in advance!

--

[George Mamalakis]

Denis,

I tried to use get_serializer_context for my project, but I got a bit confused, since the documentation you proposed me was for method-views. Then I found this link explaining how I can override get_serializer_context for GenericViews and tried to apply it on my case, with no luck. Here is my scenario:

My models:

class Report(models.Model):

    name = models.CharField(max_length=150, blank=True, null=True)

    year = models.DateField(blank=True, null=True)

    is_final = models.BooleanField(blank=True, default=False, db_index=True)

class Section(models.Model):

    name = models.CharField(max_length=500)

    text = models.Text(blank=True, null=True)

    report = models.ForeignKey(Report, related_name='sections')

class Data(models.Model):

    name = models.CharField(max_length=150)

    text = models.ForeignKey(RichText, blank=True, null=True, related_name='%(app_label)s_%(class)s_start_text')

    section = models.ForeignKey(Section, related_name='data')

    saved = models.BooleanField(default=False, db_index=True)

So, in short, I have report objects that have associated sections to them and each section has associated data. 

My views are as follows:

class ReportViewSet(viewsets.ModelViewSet):

    queryset = Report.objects.all()

    serializer_class = serializers.ReportSerializer

class SectionViewSet(viewsets.ModelViewSet):

    queryset = Section.objects.all()

    serializer_class = serializers.SectionSerializer

class DataViewSet(viewsets.ModelViewSet):

    queryset = Data.objects.all()

    serializer_class = serializers.DataSerializer

And my serializers are as follows:

class DataSerializer(serializers.HyperlinkedModelSerializer):

    class Meta:

        model = EmissionGroup

class SectionSerializer(serializers.HyperlinkedModelSerializer):

    class Meta:

        model = Section

class ReportSerializer(serializers.HyperlinkedModelSerializer):

     sections = SectionSerializer(many=True, read_only=True)

     class Meta:

        model = Report

What I am trying to do is to add an extra boolean field on my SectionSerializer (named, eg. all_saved), whose value will be True if all its related Data.saved values are also True.

When I tried to override get_serializer_context on SectionViewSet to test how it works, I've made the following changes:

class SectionViewSet(viewsets.ModelViewSet):

    queryset = Section.objects.all()

    serializer_class = serializers.SectionSerializer

    def get_serializer_context(self):

        context = super(SectionViewSet, self).get_serializer_context()

        context.update({'x': '11'})

        return context

class SectionSerializer(serializers.HyperlinkedModelSerializer):

    all_saved = serializers.SerializerMethodField('get_x')

    

    def get_x(self, instance):

        return self.context['xx']

    class Meta:

        model = Section

Then when I was viewing /section/ everything worked as expected, but when I was viewing /report/ I was getting the error:

KeyError at /report/

'x'

Request Method: GET

Request URL: http://localhost:8000/report/

Django Version: 1.6.1

Exception Type: KeyError

Exception Value: 'x'

Exception Location: /path/to/serializers.py in get_x, line 129

And the truth is that SectionViewSet.get_serializer_context() never gets called (I can infer this since my debugger never stops at a break-point that I am placing in this function).

What is the correct way of using additional context in my case?

Thanx again for your time!

On Friday, February 7, 2014 10:55:35 AM UTC+2, Denis Cornehl wrote:

Hi George, 

you can override "get_serializer_context" in your view. Then you will be able to access the information inside the serializer by using self.context. 

Alternative is to provide the data in view-methods. The view is in the serializer-context  by default (self.context['view]). 

2014-02-07 George Mamalakis <mam...@gmail.com>:

Hello everybody,

Is there I way I could process more context on my ModelSerializer other than that of my model? I wish, for example, to pass additional information on listing, that are not stored in the model my Serializer is connected.

Thanx all in advance!

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[George Mamalakis]

Correction. On:

    def get_x(self, instance):

        return self.context['xx']

what I am really using is:

    def get_x(self, instance):

        return self.context['x']

Sorry, this was just a spelling mistake.

[Denis Cornehl]

Hi George, 

have you added "x" to the context of the reportviewset? 

The context is created in the viewset and is used by the serializers. 

In the ReportSerializer you have a foreignkey to the SectionSerializer, but since you are (at this moment) in the ReportViewSet, the context does not contain "x". 

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[George Mamalakis]

Hi Denis,

Thanx again for you immediate reply. Nevertheless, I am not sure how to do what you are suggesting me to do. In my ReportSerializer I have a nested SectionSerializer (sections) to relate section objects with reports. Each section object should contain some additional information about the data objects that are associated with them. Hence, the additional context I am trying to pass is Section-related, not Report-related. Therefore, I am not sure how I can pass in my ReportViewSet Data information on each Report object's nested Section object.

On Monday, February 10, 2014 1:38:22 PM UTC+2, Denis Cornehl wrote:

Hi George, 

have you added "x" to the context of the reportviewset? 

The context is created in the viewset and is used by the serializers. 

In the ReportSerializer you have a foreignkey to the SectionSerializer, but since you are (at this moment) in the ReportViewSet, the context does not contain "x". 

2014-02-10 12:34 GMT+01:00 George Mamalakis <mam...@gmail.com>:

Correction. On:

    def get_x(self, instance):

        return self.context['xx']

what I am really using is:

    def get_x(self, instance):

        return self.context['x']

Sorry, this was just a spelling mistake.

On Friday, February 7, 2014 10:52:32 AM UTC+2, George Mamalakis wrote:

Hello everybody,

Is there I way I could process more context on my ModelSerializer other than that of my model? I wish, for example, to pass additional information on listing, that are not stored in the model my Serializer is connected.

Thanx all in advance!

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