Add ability to share answers between XBlocks, using Django models

mentoring/answer.py

@@ -9,6 +9,8 @@ from xblock.core import XBlock
 from xblock.fields import Any, Scope
 from xblock.fragment import Fragment
 
+from .models import Answer
+
 
 # Globals ###########################################################
 
@@ -26,12 +28,20 @@ class AnswerBlock(XBlock):
     """
     student_input = Any(help="Last input submitted by the student", default="", scope=Scope.user_state)
 
+    def __init__(self, *args, **kwargs):
+        super(AnswerBlock, self).__init__(*args, **kwargs)
+        if self.name:
+            self.student_input = self.get_model_object().student_input
+    
     def student_view(self, context=None):  # pylint: disable=W0613
         """Returns default student view."""
         return Fragment(u"<p>I can only appear inside problems.</p>")
 
     def mentoring_view(self, context=None):
-        html = u'<textarea cols="100" rows="10" name="input">{}</textarea>'.format(self.student_input)
+        html = u'<textarea cols="100" rows="10" maxlength="{}" name="input">{}</textarea>'.format(
+                Answer._meta.get_field('student_input').max_length,
+                self.student_input)
+
         fragment = Fragment(html)
         fragment.add_javascript("""
             function AnswerBlock(runtime, element) {
@@ -53,3 +63,25 @@ class AnswerBlock(XBlock):
         log.info(u'Answer submitted for`{}`: "{}"'.format(self.name, self.student_input))
         return self.student_input
 
+    def save(self):
+        """
+        Replicate data changes on the related Django model used for sharing of data accross XBlocks
+        """
+        super(AnswerBlock, self).save()
+        answer_data = self.get_model_object()
+        if answer_data.student_input != self.student_input:
+            answer_data.student_input = self.student_input
+            answer_data.save()
+
+    def get_model_object(self):
+        if not self.name:
+            raise ValueError, 'AnswerBlock.name field need to be set to a non-null/empty value'
+
+        # TODO Use a random user id
+        student_id = self.scope_ids.user_id
+
+        answer_data, created = Answer.objects.get_or_create(
+            student_id=student_id,
+            name=self.name
+        )
+        return answer_data

mentoring/migrations/0001_initial.py

+# -*- coding: utf-8 -*-
+import datetime
+from south.db import db
+from south.v2 import SchemaMigration
+from django.db import models
+
+
+class Migration(SchemaMigration):
+
+    def forwards(self, orm):
+        # Adding model 'Answer'
+        db.create_table('mentoring_answer', (
+            ('id', self.gf('django.db.models.fields.AutoField')(primary_key=True)),
+            ('name', self.gf('django.db.models.fields.CharField')(max_length=20, db_index=True)),
+            ('student_id', self.gf('django.db.models.fields.CharField')(max_length=20, db_index=True)),
+            ('student_input', self.gf('django.db.models.fields.CharField')(max_length=10000)),
+            ('created_on', self.gf('django.db.models.fields.DateTimeField')(auto_now_add=True, blank=True)),
+            ('modified_on', self.gf('django.db.models.fields.DateTimeField')(auto_now=True, blank=True)),
+        ))
+        db.send_create_signal('mentoring', ['Answer'])
+
+        # Adding unique constraint on 'Answer', fields ['student_id', 'name']
+        db.create_unique('mentoring_answer', ['student_id', 'name'])
+
+
+    def backwards(self, orm):
+        # Removing unique constraint on 'Answer', fields ['student_id', 'name']
+        db.delete_unique('mentoring_answer', ['student_id', 'name'])
+
+        # Deleting model 'Answer'
+        db.delete_table('mentoring_answer')
+
+
+    models = {
+        'mentoring.answer': {
+            'Meta': {'unique_together': "(('student_id', 'name'),)", 'object_name': 'Answer'},
+            'created_on': ('django.db.models.fields.DateTimeField', [], {'auto_now_add': 'True', 'blank': 'True'}),
+            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'modified_on': ('django.db.models.fields.DateTimeField', [], {'auto_now': 'True', 'blank': 'True'}),
+            'name': ('django.db.models.fields.CharField', [], {'max_length': '20', 'db_index': 'True'}),
+            'student_id': ('django.db.models.fields.CharField', [], {'max_length': '20', 'db_index': 'True'}),
+            'student_input': ('django.db.models.fields.CharField', [], {'max_length': '10000'})
+        }
+    }
+
+    complete_apps = ['mentoring']
\ No newline at end of file

mentoring/models.py

@@ -3,6 +3,10 @@ from django.db import models
 class Answer(models.Model):
     class Meta:
         app_label = 'mentoring'
+        unique_together = (('student_id', 'name'),)
 
-    text = models.CharField(max_length=2000)
-    pub_date = models.DateTimeField('date published', auto_now_add=True)
+    name = models.CharField(max_length=20, db_index=True)
+    student_id = models.CharField(max_length=20, db_index=True)
+    student_input = models.CharField(max_length=10000)
+    created_on = models.DateTimeField('created on', auto_now_add=True)
+    modified_on = models.DateTimeField('modified on', auto_now=True)