我为此目的放置了我项目的一部分，并为没有在此答案中总结代码而道歉（因为我认为总结它可能会在没有测试的情况下出错，所以我决定使用复制粘贴经过测试的代码）。
当我想读取四个嵌套的 Django 管理模型（4D）并在代码中使用它们时，我做了以下过程：
models.py：
from __future__ import unicode_literals
from django.db import models
from django.db.models.deletion import CASCADE
MODBUS_TYPES = (('tcp', 'Tcp'), ('udp', 'Udp'), ('ascii', 'Ascii'), ('rtu', 'Rtu'))
class BatteryMonitoringServer(models.Model):
enable = models.BooleanField(default=True)
name = models.CharField(max_length=150)
server_ip = models.GenericIPAddressField(default='0.0.0.0', null=True)
def __str__(self):
return self.name
class BatteryMonitoringDevice(models.Model):
bm_id = models.ForeignKey(BatteryMonitoringServer, on_delete=CASCADE)
enable = models.BooleanField(default=True)
name = models.CharField(max_length=100, null=True)
method = models.CharField(max_length=5, choices=MODBUS_TYPES)
bm_device_ip = models.GenericIPAddressField(default='127.0.0.1', null=True)
bm_device_port = models.IntegerField(default=5558, null=True)
baud_rate = models.IntegerField(null=True, default=9600)
class BatteryMonitoringSubDevice(models.Model):
enable = models.BooleanField(default=True)
name = models.CharField(max_length=100)
unit = models.IntegerField(default=1)
sub_bm_count = models.IntegerField(default=4, null=True, blank=True, name='bm')
fk = models.ForeignKey(BatteryMonitoringDevice, on_delete=CASCADE)
class BatteryMonitoringMeta(models.Model):
key = models.CharField(max_length=100)
value = models.CharField(max_length=100)
module = models.ForeignKey(BatteryMonitoringSubDevice, on_delete=CASCADE)
conf_reader.py
from battery_monitoring.models import BatteryMonitoringServer
from delta_device.utility import DictEncoder
class BMSubDeviceConf(object):
def __init__(
self,
start,
name,
unit,
bm,
meta_data):
self._start = start
self._name = name
self._unit = unit
self._bm = bm
self._meta_data = meta_data
@property
def start(self):
return self._start
@property
def name(self):
return self._name
@property
def unit(self):
return self._unit
@property
def bm(self):
return self._bm
@property
def meta_data(self):
return self._meta_data
class BMDeviceConf(object):
def __init__(
self,
bm_id,
start,
name,
method,
bm_device_ip,
bm_device_port,
baud_rate,
sub_devices=None):
self._id = bm_id
self._start = start
self._name = name
self._method = method
self._bm_device_ip = bm_device_ip
self._bm_device_port = bm_device_port
self._baud_rate = baud_rate
self._sub_devices = sub_devices or []
def add_sub_device(self, sub_device):
self._sub_devices.append(sub_device)
def get_sub_devices(self):
return self._sub_devices
@property
def start(self):
return self._start
@property
def id(self):
return self._id
@property
def name(self):
return self._name
@property
def bm_device_ip(self):
return self._bm_device_ip
@property
def bm_device_port(self):
return self._bm_device_port
@property
def baud_rate(self):
return self._baud_rate
class BMConf(object):
def __init__(
self,
start,
name,
server_ip,
devices=None,
): # :( :| :) (: :p
self._start = 'ON' if start else 'OFF'
self._name = name
self._server_ip = server_ip
self._devices = devices or []
def add_device(self, device):
self._devices.append(device)
def get_devices(self):
return self._devices
@property
def start(self):
return self._start
@property
def name(self):
return self._name
@property
def server_ip(self):
return self._server_ip
def get_server():
"""Using list method to make a fast sql reading."""
return list(BatteryMonitoringServer.objects.all())
def get_devices(dev):
return list(dev.batterymonitoringdevice_set.all())
def get_sub_devices(sub_dev):
return list(sub_dev.batterymonitoringsubdevice_set.all())
def get_metadata(metric):
return list(metric.batterymonitoringmeta_set.all())
class BMReadConf(object):
"""BM configuration Reader"""
def __init__(self):
pass
@classmethod
def get_bm_config(cls):
"""Read BM metrics and return it on a object list"""
result = list()
for srv in get_server():
data = BMConf(srv.enable,
srv.name,
srv.server_ip,)
for dev in get_devices(srv):
device = BMDeviceConf(
dev.bm_id,
dev.enable,
dev.name,
dev.method,
dev.bm_device_ip,
dev.bm_device_port,
dev.baud_rate,
)
for sub_dev in get_sub_devices(dev):
meta_data = {}
for meta in get_metadata(sub_dev):
meta_data[meta.key] = meta.value
sub_device = BMSubDeviceConf(
sub_dev.enable,
sub_dev.name,
sub_dev.unit,
sub_dev.bm,
meta_data,
)
device.add_sub_device(sub_device)
data.add_device(device)
result.append(data)
return result
用法（test.py）
from battery_monitoring.conf_reader import BMReadConf
conf_obj = BMReadConf()
configs = conf_obj.get_bm_config()
for cnf in configs:
print(cnf.name) # This is name field in BatteryMonitoringServer Table.
devices = cnf.get_devices()
for dev in devices:
print(dev.baud_rate) # This is baud_rate field in second nested table.
sub_devices = dev.get_sub_devices()
for sub_dev in sub_devices:
print(sub_dev.unit) # This is unit field in third nested table.
print(sub_dev.meta_data) # This is meta_data table (fourth nested table).
我希望这会很有用。
[注意]：
第四个嵌套表（meta_data）有一个递增的键/值字段。