以公里或米为单位显示每家餐厅的距离

Question

我已经使用 postgis 和 geodjango 实现了从给定坐标显示附近餐厅的功能。但是我需要根据用户附近的距离或给定的坐标找到以公里或米为单位的距离。我知道在 SO 中提出了与距离相关的问题，但这个问题有点不同。我正在显示餐厅列表（列表视图）而不是餐厅的详细信息，我将从 id 获得特定的餐厅位置。所以我需要一个想法，我现在应该如何在餐厅列表视图中显示每家餐厅的距离。

我的想法是我应该通过 lat 和 lng（我从 url 传递）作为上下文并使用模板过滤器来计算距离

from django.contrib.gis.geos import GEOSGeometry
pnt = GEOSGeometry('SRID=4326;POINT(40.396764 -3.68042)')
pnt2 = GEOSGeometry('SRID=4326;POINT( 48.835797 2.329102  )')
pnt.distance(pnt2)*100

这里是详细代码

def nearby_restaurant_finder(request, current_lat, current_long):
    from django.contrib.gis.geos import Point
    from django.contrib.gis.measure import D

    user_location = Point(float(current_long), float(current_lat))
    distance_from_point = {'km': 500}
    restaurants = Restaurant.gis.filter(
        location__distance_lte=(user_location, D(**distance_from_point)))
    restaurants = restaurants.distance(user_location).order_by('distance')
    context = {
        'restaurants': restaurants
    }
    return render(request, 'restaurant/nearby_restaurant.html', context)


 url(r'^nearby_restaurant/(?P<current_lat>-?\d*.\d*)/(?P<current_long>-?\d*.\d*)/$',
        views.nearby_restaurant_finder, name="nearby-restaurant"),


{% block page %}
    {% for restaurant in restaurants %}
        <h1>Nearby Restaurants are:</h1>
        <h3>{{ restaurant.name }}</h3>
        {% empty %}
        <h3>No Match Found</h3>
    {% endfor %}
{% endblock %}

请分享您对我应该如何做的想法

Answer 1

我想你快到了；我会使用 python 计算距离，然后将它们显示在模板中，而不是创建过滤器。

我会首先使用字典列表或类似列表来更新上下文：

def calculate_distance(restaurant_location, current_lat, current_long):
    # this function should return the distance of the restaurant from the user
    return distance_calculated

def nearby_restaurant_finder(request, current_lat, current_long):
    from django.contrib.gis.geos import Point
    from django.contrib.gis.measure import D

    user_location = Point(float(current_long), float(current_lat))
    distance_from_point = {'km': 500}
    restaurants = Restaurant.gis.filter(location__distance_lte=(user_location, D(**distance_from_point)))
    restaurants = restaurants.distance(user_location).order_by('distance')

    # create a list of dictionaries with results to display
    ctx_restaurants = [
        {
            'name': restaurant.name, 
            'distance_from_user': calculate_distance(restaurant.location, current_lat, current_long)
        }
        for restaurant in restaurants
    ]

    # pass results into context
    context = {
        'restaurants': ctx_restaurants
    }
    return render(request, 'restaurant/nearby_restaurant.html', context)

然后我会在模板中以某种表格的形式呈现它

{% block page %}
    <h1>Nearby Restaurants are:</h1>
    <table>
    {% for restaurant in restaurants %}
        <tr>
        <td>{{ restaurant.name }}</td>
        <td>{{ restaurant.distance_from_user}}</td>
        </tr>
    {% endfor %}
    </table>
{% endblock %}

使用 TDD： 由于calculate_distance() 是解耦的，我会通过一堆已知距离来测试它。根据the testing docs设置你的测试

from django.test import TestCase
from myapp.views import calculate_distance

class DistanceTests(TestCase):
    def setUp(self):
        self.known_cases = [
            {'location': XX1, 'lat': XX1, 'long': XX1, 'expected': XX1},
            {'location': XX2, 'lat': XX2, 'long': XX2, 'expected': XX2},
        ]

    def test_calculate_distance(self):
        for case in self.known_cases:
            self.assertEquals(
                calculate_distance(case['location'], case['lat'], case['long']),
                case['expected']
            )