Child model updates Parent model in Django ForeignKey relationship
Assuming the following models schema,
Parent model:
class Batch(models.Model):
start = models.DateTimeField()
end = models.DateTimeField()
One of many child models:
class Data(models.Model):
batch = models.ForeignKey(Batch, on_delete=models.ON_CASCADE)
timestamp = models.DateTimeField()
My goals is the following: to have a start field of parent model that is always updated when any child model is modified.
Basically, if the timestamp of a newly data instance is older than the start field I want the start field to be updated to that instance timestamp value. In the case of deletion of the data instance which is the oldest time reference point I want batch start field to be updated to the second oldest. Vice-versa for the end field.
django
asked Nov 12 at 12:25
André Guerra
27110
add a comment |
Assuming the following models schema,
Parent model:
class Batch(models.Model):
start = models.DateTimeField()
end = models.DateTimeField()
One of many child models:
class Data(models.Model):
batch = models.ForeignKey(Batch, on_delete=models.ON_CASCADE)
timestamp = models.DateTimeField()
My goals is the following: to have a start field of parent model that is always updated when any child model is modified.
Basically, if the timestamp of a newly data instance is older than the start field I want the start field to be updated to that instance timestamp value. In the case of deletion of the data instance which is the oldest time reference point I want batch start field to be updated to the second oldest. Vice-versa for the end field.
django
asked Nov 12 at 12:25
André Guerra
27110
add a comment |
Assuming the following models schema,
Parent model:
class Batch(models.Model):
start = models.DateTimeField()
end = models.DateTimeField()
One of many child models:
class Data(models.Model):
batch = models.ForeignKey(Batch, on_delete=models.ON_CASCADE)
timestamp = models.DateTimeField()
My goals is the following: to have a start field of parent model that is always updated when any child model is modified.
Basically, if the timestamp of a newly data instance is older than the start field I want the start field to be updated to that instance timestamp value. In the case of deletion of the data instance which is the oldest time reference point I want batch start field to be updated to the second oldest. Vice-versa for the end field.
django
asked Nov 12 at 12:25
André Guerra
27110
Assuming the following models schema,
Parent model:
class Batch(models.Model):
start = models.DateTimeField()
end = models.DateTimeField()
One of many child models:
class Data(models.Model):
batch = models.ForeignKey(Batch, on_delete=models.ON_CASCADE)
timestamp = models.DateTimeField()
My goals is the following: to have a start field of parent model that is always updated when any child model is modified.
Basically, if the timestamp of a newly data instance is older than the start field I want the start field to be updated to that instance timestamp value. In the case of deletion of the data instance which is the oldest time reference point I want batch start field to be updated to the second oldest. Vice-versa for the end field.
django
django
asked Nov 12 at 12:25
André Guerra
27110
asked Nov 12 at 12:25
André Guerra
27110
asked Nov 12 at 12:25
André Guerra
27110
asked Nov 12 at 12:25
André Guerra
27110
asked Nov 12 at 12:25
André Guerra
27110
27110
add a comment |
add a comment |
2 Answers
2
active
oldest
votes
One of the possible way to do this is to add post or pre-save signal of relative models and Update your necessary fields according to this. Django official documentation for signal, link. I want to add another link, one of the best blog post i have seen regarding django signal.
Edit for André Guerra response
One of easiest way to do a get call and bring Batch instance. What i want to say
@receiver(post_save,sender=Data)
def on_batch_child_saving(sender,instance,**kwargs):
batch_instance = Batch.objects.get(pk=instance.batch)
if (instance.timestamp < batch_instance.start):
batch_instance.start = instance.timestamp
batch_instance.save()
elif (instance.timestamp > batch_instance.end):
batch_instance.end = instance.timestamp
batch_instance.save()
answered Nov 12 at 12:40
Shakil
4371313
add a comment |
Based on Shakil suggestion, I come up with this: (my doubt here was on how to save the parent model)
@receiver(post_save,sender=Data)
def on_batch_child_saving(sender,instance,**kwargs):
if (instance.timestamp < instance.batch.start):
instance.batch.start = instance.timestamp
instance.batch.save()
elif (instance.timestamp > instance.batch.end):
instance.batch.end = instance.timestamp
instance.batch.save()
answered Nov 12 at 14:41
André Guerra
27110
1
I have updated my answer, you can check it.
– Shakil
Nov 12 at 15:48
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
One of the possible way to do this is to add post or pre-save signal of relative models and Update your necessary fields according to this. Django official documentation for signal, link. I want to add another link, one of the best blog post i have seen regarding django signal.
Edit for André Guerra response
One of easiest way to do a get call and bring Batch instance. What i want to say
@receiver(post_save,sender=Data)
def on_batch_child_saving(sender,instance,**kwargs):
batch_instance = Batch.objects.get(pk=instance.batch)
if (instance.timestamp < batch_instance.start):
batch_instance.start = instance.timestamp
batch_instance.save()
elif (instance.timestamp > batch_instance.end):
batch_instance.end = instance.timestamp
batch_instance.save()
answered Nov 12 at 12:40
Shakil
4371313
add a comment |
One of the possible way to do this is to add post or pre-save signal of relative models and Update your necessary fields according to this. Django official documentation for signal, link. I want to add another link, one of the best blog post i have seen regarding django signal.
Edit for André Guerra response
One of easiest way to do a get call and bring Batch instance. What i want to say
@receiver(post_save,sender=Data)
def on_batch_child_saving(sender,instance,**kwargs):
batch_instance = Batch.objects.get(pk=instance.batch)
if (instance.timestamp < batch_instance.start):
batch_instance.start = instance.timestamp
batch_instance.save()
elif (instance.timestamp > batch_instance.end):
batch_instance.end = instance.timestamp
batch_instance.save()
answered Nov 12 at 12:40
Shakil
4371313
add a comment |
One of the possible way to do this is to add post or pre-save signal of relative models and Update your necessary fields according to this. Django official documentation for signal, link. I want to add another link, one of the best blog post i have seen regarding django signal.
Edit for André Guerra response
One of easiest way to do a get call and bring Batch instance. What i want to say
@receiver(post_save,sender=Data)
def on_batch_child_saving(sender,instance,**kwargs):
batch_instance = Batch.objects.get(pk=instance.batch)
if (instance.timestamp < batch_instance.start):
batch_instance.start = instance.timestamp
batch_instance.save()
elif (instance.timestamp > batch_instance.end):
batch_instance.end = instance.timestamp
batch_instance.save()
answered Nov 12 at 12:40
Shakil
4371313
One of the possible way to do this is to add post or pre-save signal of relative models and Update your necessary fields according to this. Django official documentation for signal, link. I want to add another link, one of the best blog post i have seen regarding django signal.
Edit for André Guerra response
One of easiest way to do a get call and bring Batch instance. What i want to say
@receiver(post_save,sender=Data)
def on_batch_child_saving(sender,instance,**kwargs):
batch_instance = Batch.objects.get(pk=instance.batch)
if (instance.timestamp < batch_instance.start):
batch_instance.start = instance.timestamp
batch_instance.save()
elif (instance.timestamp > batch_instance.end):
batch_instance.end = instance.timestamp
batch_instance.save()
answered Nov 12 at 12:40
Shakil
4371313
edited Nov 12 at 15:47
answered Nov 12 at 12:40
Shakil
4371313
answered Nov 12 at 12:40
Shakil
4371313
answered Nov 12 at 12:40
Shakil
4371313
4371313
add a comment |
add a comment |
Based on Shakil suggestion, I come up with this: (my doubt here was on how to save the parent model)
@receiver(post_save,sender=Data)
def on_batch_child_saving(sender,instance,**kwargs):
if (instance.timestamp < instance.batch.start):
instance.batch.start = instance.timestamp
instance.batch.save()
elif (instance.timestamp > instance.batch.end):
instance.batch.end = instance.timestamp
instance.batch.save()
answered Nov 12 at 14:41
André Guerra
27110
1
I have updated my answer, you can check it.
– Shakil
Nov 12 at 15:48
add a comment |
Based on Shakil suggestion, I come up with this: (my doubt here was on how to save the parent model)
@receiver(post_save,sender=Data)
def on_batch_child_saving(sender,instance,**kwargs):
if (instance.timestamp < instance.batch.start):
instance.batch.start = instance.timestamp
instance.batch.save()
elif (instance.timestamp > instance.batch.end):
instance.batch.end = instance.timestamp
instance.batch.save()
answered Nov 12 at 14:41
André Guerra
27110
1
I have updated my answer, you can check it.
– Shakil
Nov 12 at 15:48
add a comment |
Based on Shakil suggestion, I come up with this: (my doubt here was on how to save the parent model)
@receiver(post_save,sender=Data)
def on_batch_child_saving(sender,instance,**kwargs):
if (instance.timestamp < instance.batch.start):
instance.batch.start = instance.timestamp
instance.batch.save()
elif (instance.timestamp > instance.batch.end):
instance.batch.end = instance.timestamp
instance.batch.save()
answered Nov 12 at 14:41
André Guerra
27110
Based on Shakil suggestion, I come up with this: (my doubt here was on how to save the parent model)
@receiver(post_save,sender=Data)
def on_batch_child_saving(sender,instance,**kwargs):
if (instance.timestamp < instance.batch.start):
instance.batch.start = instance.timestamp
instance.batch.save()
elif (instance.timestamp > instance.batch.end):
instance.batch.end = instance.timestamp
instance.batch.save()
answered Nov 12 at 14:41
André Guerra
27110
answered Nov 12 at 14:41
André Guerra
27110
answered Nov 12 at 14:41
André Guerra
27110
answered Nov 12 at 14:41
André Guerra
27110
27110
1
I have updated my answer, you can check it.
– Shakil
Nov 12 at 15:48
add a comment |
1
I have updated my answer, you can check it.
– Shakil
Nov 12 at 15:48
1
1
I have updated my answer, you can check it.
– Shakil
Nov 12 at 15:48
I have updated my answer, you can check it.
– Shakil
Nov 12 at 15:48
add a comment |
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