Hi, Ryan.
> I'm working on a server project for a petrol station company.
> I have this station class.
>
> class Station(modelpy.Model):
> shifts = ndb.JsonProperty()
>
> The Station's key's id is the name of a station.
> Here are the names of the actual stations: "West Coast", "Woodlands",
> "South View".
> I use these station names in get_by_id() to get the station entity.
> As you can see, Station consists of a JsonProperty called "shifts".
> The "shifts" consists of the data as follows (shown in a json format):
> {
> "South View": {
> "shifts": {
> "Full Day": {
> "start": "7am",
> "end": "7pm"
> }
> }
> },
> "West Coast": {
> "shifts": {
> "Morning Shift": {
> "start": "10am",
> "end": "10pm"
> },
> "Night Shift": {
> "start": "10pm",
> "end": "10am"
> }
> }
> },
> "Woodlands": {
> "shifts": {
> "Morning Shift": {
> "start": "8am",
> "end": "8pm"
> },
> "Night Shift": {
> "start": "8pm",
> "end": "8am"
> }
> }
> }
> }
> I need a solution for these 3:
> 1) Ndb must not be allowed to store more than 1 shift (e.g. key.put()
> replaces any (if existing) entity with equal id).
> 2) Ndb must contain the "start" and "end" required property for every
> shift (e.g. required=True).
> 3) Most IMPORTANT: A MAINTAINTABLE solution that does not need to be
> re-implemented for other similar examples. (e.g. NOT write custom assertion
> every single time!)
>
>
Maybe, something like this?
class Shifts(modelpy.Model):
start = ndb.StringProperty(default='')
end = ndb.StringProperty(default='')
def convert_json_to_ndb():
# assume, that Station contain small amount of records
for station in Station.query():
for key, props in station.shifts.items():
Shifts(
id=key,
parent=station.key,
start=props['start'],
end=props['end'],
).put()
Then, access to shifts:
west_coast_shifts = Station.query(ancestor=ndb.Key(Station, 'West Coast'))
for item in west_coast_shifts:
print "name", item.key.id(), "start", item.start, "end", item.end
WBR, Vitaly
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