Question

任何人都可以使用GeoAlchemy为Flask提供任何示例代码吗？

Answer 1

使用SQLAlchemy 0.8，Flask-SQLAlchemy和Geoalchemy 2：

from app import db
from geoalchemy2.types import Geometry

class Point(db.Model):

    """represents an x/y coordinate location."""

    __tablename__ = 'point'

    id = db.Column(db.Integer, primary_key=True)
    geom = db.Column(Geometry(geometry_type='POINT', srid=4326))

示例查询：

from geoalchemy2.elements import WKTElement
from app import models

def get_nearest(lat, lon):
    # find the nearest point to the input coordinates
    # convert the input coordinates to a WKT point and query for nearest point
    pt = WKTElement('POINT({0} {1})'.format(lon, lat), srid=4326)
    return models.Point.query.order_by(models.Point.geom.distance_box(pt)).first()

将结果转换为x和y坐标（转换为GeoJSON并提取坐标）的一种方法：

import geoalchemy2.functions as func
import json
from app import db

def point_geom_to_xy(pt):
    # extract x and y coordinates from a point geometry
    geom_json = json.loads(db.session.scalar(func.ST_AsGeoJSON(pt.geom)))
    return geom_json['coordinates']

Answer 2

如果您不仅限于使用Flask，您可能需要尝试MapFish，这是基于Pylons并使用GeoAlchemy。

Answer 3

您可以将它与Flask-SQLAlchemy一起使用，但您也可以将它与普通的SQLAlchemy一起使用。只需将sample models from GeoAlchemy翻译为Flask-SQLAlchemy即可。像这样：

class Spot(db.Model):
    __tablename__ = 'spots'
    id = db.Column(Integer, primary_key=True)
    name = db.Column(Unicode, nullable=False)
    height = db.Column(Integer)
    created = db.Column(DateTime, default=datetime.now())
    geom = db.GeometryColumn(Point(2))

我没有测试过代码，但它应该是一个公平的转录。

Answer 4

from myapp import db
from geoalchemy import GeometryColumn, Point

class FixXX(db.Model):

    __tablename__ = 'fixXX'

    fix_pk = db.Column(db.Integer, primary_key=True)
    fix = db.Column(db.String)
    geometry = GeometryColumn(Point(2, srid=4326))

GeometryDDL(FixXX.__table__)

带有GeoAlchemy示例代码的Flask

4 个答案: