diff value with the previous measure or with the first one

heima/sherlock/admin.py

@@ -7,7 +7,7 @@ from .models import Category, Gauge, Measure
 class MeasureAdmin(admin.ModelAdmin):
     model = Measure
 
-    list_display = ('__str__', 'value', 'category')
+    list_display = ('__str__', 'value', 'category', 'previous_diff', 'longest_diff')
     list_filter = ('gauge__category',)
 
 admin.site.register(Category)

heima/sherlock/models.py

@@ -81,6 +81,20 @@ class Measure(models.Model):
 
         return self.value - other_measure.value
 
+    @property
+    def previous_diff(self):
+        try:
+            return DiffMeasure(self, self.previous).daily_average_increase()
+        except:
+            return '?'
+ 
+    @property
+    def longest_diff(self):
+        try:
+            return DiffMeasure(self, self.gauge.measures.last()).daily_average_increase()
+        except:
+            return '?'
+
     @property
     def category(self):
         return self.gauge.category
@@ -98,3 +112,4 @@ class Measure(models.Model):
             return self.gauge.measures.filter(moment__gt=self.moment).order_by('moment')[0]
         except IndexError:
             return None
+