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我通过构建非常小规模的应用程序来练习 django。我已经使用 3 个表创建了一个航班预订系统——机场、航班、乘客。这是我的模型类-

from django.db import models

# Create your models here.
class Airport(models.Model):
    code = models.CharField(max_length=3)
    city = models.CharField(max_length=64)

    def __str__(self):
        return f"{self.city} ({self.code})"

class Flight(models.Model):
    origin = models.ForeignKey(Airport, on_delete = models.CASCADE, related_name="departures")
    destination = models.ForeignKey(Airport, on_delete = models.CASCADE, related_name = "arrivals")
    duration = models.IntegerField()

    def __str__(self):
        return f"{self.id} {self.origin} to {self.destination}"

# A flight can have multiple passengers or a passenger can board on multiple flights
class Passenger(models.Model):
    first = models.CharField(max_length=64)
    last = models.CharField(max_length=64)

    # flights establishes many to many relationship with Flight table
    flights = models.ManyToManyField(Flight, blank=True, related_name="passengers")

    def __str__(self):
        return f"{self.first} {self.last}"

我已设法显示乘客列表并为特定乘客预订了航班，但我无法从特定航班中删除乘客。问题是我还没有清楚地理解 django 模型中的多对多关系。这是我的视图函数的代码片段-

from django.shortcuts import render
from django.http import HttpResponseRedirect
from django.urls import reverse
from .models import *

# Create your views here.
def index(request):
    return render(request, "flights/index.html",{
        "flights":Flight.objects.all(),
    })

def flight(request, flight_id):
    flight = Flight.objects.get(pk=flight_id)

    #Get all the passengers who are present on the flight 
    passengers = flight.passengers.all()

    #Returns a new QuerySet containing objects that do not match the given lookup parameters.
    non_passengers = Passenger.objects.exclude(flights=flight).all() # Returns all the passenger who are not on the particular flight
    return render(request, "flights/flight.html", {
        "flight":flight,
        "passengers":passengers,
        "non_passengers":non_passengers,
    })

def book(request, flight_id):
    if request.method == "POST":

        #Access the the flight by specifying the primary key
        flight = Flight.objects.get(pk=flight_id)

        #Finding the passenger id and passenger from submitted data
        passenger = Passenger.objects.get(pk=int(request.POST["passenger"]))
        
        #Add passenger to the flight
        passenger.flights.add(flight)

        #Redirect the user to flight page
        return HttpResponseRedirect(reverse("flight", args=(flight.id,)))

def delete(request, flight_id):
    if request.method == "POST":

        #Access the the flight by specifying the primary key
        flight = Flight.objects.get(pk=flight_id)

        #Finding the passenger id and passenger from submitted data
        passenger_id = Passenger.objects.get(pk=int(request.POST["passenger"]))
        print(passenger)
        
        #Remove passenger from the flight     
        passenger.flight.delete(passenger_id)
        
        #Redirect the user to flight page
        return HttpResponseRedirect(reverse("flight", args=(flight.id)))

这是我用于显示预订系统的 HTML -

    {% extends "flights/layout.html" %}
    
    {% block body %}
        <h1>Flight {{ flight.id }}</h1>
        <ul>
            <li>Origin: {{ flight.origin }}</li>
            <li>Destination: {{ flight.destination }}</li>
            <li>Duration: {{ flight.duration }}</li>
        </ul>
    
        <h3>Passengers</h3>
        <ul>
            {% for passenger in passengers %} 
                <li>{{passenger}}</li>
            {% empty %}
            <li>No passengers</li>
            {% endfor %}
        </ul>
    
        <h2>Add Passenger</h2>
        <form action="{% url 'book' flight.id %}" method="POST">
            {% csrf_token %}
            <select name="passenger" id="">
                {% for passenger in non_passengers %} 
                    <option value="{{passenger.id}}">{{ passenger }}</option>
                {% endfor %}
            </select>
            <input type="submit">    
            </form>
    
        <h2>Delete Passenger</h2>
        <form action="{% url 'delete' flight.id %}" method="POST">
            {% csrf_token %}
            <select name="passenger" id="">
                {% for passenger in passengers %} 
                    <option value="{{passenger.id}}">{{ passenger }}</option>
                {% endfor %}
            </select>
            <input type="submit">    
        </form>

    <a href="{% url 'index' %}">Back to Flight List</a>
{% endblock %}

谁能向我解释 django 中的多对多关系并建议我如何从特定航班中删除乘客（或取消他的预订）？

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0 回答 0