尝试从纬度/纬度创建点时出现 RGeo 错误

我正在编写一个应用程序，我正在尝试集成一些通用的地理位置功能，包括将一些纬度/纬度坐标保存为数据库中的点。这样做的目的是允许用户使用他们的位置（由设备提供）或谷歌地图标记来选择他们的坐标。我已经成功地从地图或设备中获取坐标，但是我现在无法从它们创建一个点以保存到数据库中。

我已经阅读了文档并尝试将此代码添加到我的初始值设定项中：

初始值设定项/rgeo.rb

require 'rgeo-activerecord' 
RGeo::ActiveRecord::SpatialFactoryStore.instance.tap do |config|
  # By default, use the GEOS implementation for spatial columns.
  config.default = RGeo::Geos.factory_generator
  # But use a geographic implementation for point columns.
  config.register(RGeo::Geographic.spherical_factory(srid: 4326), geo_type: "point")
end

宝石文件：

gem 'activerecord-postgis-adapter'
gem 'rgeo'
gem 'rgeo-activerecord'

迁移：

def change
 add_column :monuments, :grid_ref, :point, geographic: true
end

尝试创建点时，我在 rails 控制台中收到此错误：

irb(main):004:0> m.grid_ref = "POINT(-122.193963 47.675086)"
ArgumentError: invalid value for Float(): "POINT(-122.193963 47.675086)"
    from /usr/local/lib/ruby/gems/2.2.0/gems/activerecord-4.2.0/lib/active_record/connection_adapters/postgresql/oid/point.rb:20:in `Float'
    from /usr/local/lib/ruby/gems/2.2.0/gems/activerecord-4.2.0/lib/active_record/connection_adapters/postgresql/oid/point.rb:20:in `block in type_cast'
    from /usr/local/lib/ruby/gems/2.2.0/gems/activerecord-4.2.0/lib/active_record/connection_adapters/postgresql/oid/point.rb:20:in `map'
    from /usr/local/lib/ruby/gems/2.2.0/gems/activerecord-4.2.0/lib/active_record/connection_adapters/postgresql/oid/point.rb:20:in `type_cast'
    from /usr/local/lib/ruby/gems/2.2.0/gems/activerecord-4.2.0/lib/active_record/connection_adapters/postgresql/oid/point.rb:18:in `type_cast'
    from /usr/local/lib/ruby/gems/2.2.0/gems/activerecord-4.2.0/lib/active_record/type/value.rb:23:in `type_cast_from_database'
    from /usr/local/lib/ruby/gems/2.2.0/gems/activerecord-4.2.0/lib/active_record/type/mutable.rb:5:in `type_cast_from_user'
    from /usr/local/lib/ruby/gems/2.2.0/gems/activerecord-4.2.0/lib/active_record/attribute.rb:100:in `type_cast'
    from /usr/local/lib/ruby/gems/2.2.0/gems/activerecord-4.2.0/lib/active_record/attribute.rb:42:in `original_value'
    from /usr/local/lib/ruby/gems/2.2.0/gems/activerecord-4.2.0/lib/active_record/attribute.rb:37:in `value'
    from /usr/local/lib/ruby/gems/2.2.0/gems/activerecord-4.2.0/lib/active_record/attribute.rb:46:in `value_for_database'
    from /usr/local/lib/ruby/gems/2.2.0/gems/activerecord-4.2.0/lib/active_record/attribute_methods/dirty.rb:164:in `store_original_raw_attribute'
    from /usr/local/lib/ruby/gems/2.2.0/gems/activerecord-4.2.0/lib/active_record/attribute_methods/dirty.rb:93:in `write_attribute'
    from /usr/local/lib/ruby/gems/2.2.0/gems/activerecord-4.2.0/lib/active_record/attribute_methods.rb:50:in `__temp__76279646f5275666'
    from (irb):4
    from /usr/local/lib/ruby/gems/2.2.0/gems/railties-4.2.0/lib/rails/commands/console.rb:110:in `start'
... 9 levels...
    from /usr/local/lib/ruby/gems/2.2.0/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:268:in `load'
    from /usr/local/lib/ruby/gems/2.2.0/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:268:in `block in load'
    from /usr/local/lib/ruby/gems/2.2.0/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:240:in `load_dependency'
    from /usr/local/lib/ruby/gems/2.2.0/gems/activesupport-4.2.0/lib/active_support/dependencies.rb:268:in `load'
    from /usr/local/lib/ruby/gems/2.2.0/gems/spring-1.6.4/lib/spring/commands/rails.rb:6:in `call'
    from /usr/local/lib/ruby/gems/2.2.0/gems/spring-1.6.4/lib/spring/command_wrapper.rb:38:in `call'
    from /usr/local/lib/ruby/gems/2.2.0/gems/spring-1.6.4/lib/spring/application.rb:185:in `block in serve'
    from /usr/local/lib/ruby/gems/2.2.0/gems/spring-1.6.4/lib/spring/application.rb:156:in `fork'
    from /usr/local/lib/ruby/gems/2.2.0/gems/spring-1.6.4/lib/spring/application.rb:156:in `serve'
    from /usr/local/lib/ruby/gems/2.2.0/gems/spring-1.6.4/lib/spring/application.rb:131:in `block in run'
    from /usr/local/lib/ruby/gems/2.2.0/gems/spring-1.6.4/lib/spring/application.rb:125:in `loop'
    from /usr/local/lib/ruby/gems/2.2.0/gems/spring-1.6.4/lib/spring/application.rb:125:in `run'
    from /usr/local/lib/ruby/gems/2.2.0/gems/spring-1.6.4/lib/spring/application/boot.rb:18:in `<top (required)>'
    from /usr/local/lib/ruby/site_ruby/2.2.0/rubygems/core_ext/kernel_require.rb:55:in `require'
    from /usr/local/lib/ruby/site_ruby/2.2.0/rubygems/core_ext/kernel_require.rb:55:in `require'

在阅读此演示后，我采用了这种方法，这表明该模型隐式理解 WKT 字符串，并在内部将其转换为"点"对象。

找到了解决方案。必须指定 SRID，geographic_factory现在已spherical_factory，并且点是在指定 SRID 的球形工厂上调用的方法。

目前，我已经实现了以下辅助方法，它适用于rails 4.2.6，postgis和postgresql。

请注意，工厂首先采用经度参数:)

def set_latlon(lat, lng)
  factory = RGeo::Geographic.spherical_factory(srid: 4326)
  # NOTE: this method takes the LNG parameter first!
  self.latlon = factory.point(lng, lat)
end

继续前进，

如果您遵循与我相同的空间配置教程，您会注意到以这种方式创建的行将失败。我通过将:point列替换为:geographic列来解决此问题。迁移代码如下。

class Location < ActiveRecord::Migration
  def change
    remove_column :locations, :latlon # formerly of type :point
    add_column :locations, :latlon, :geography, limit: {:srid=>4326, :type=>"point", :geographic=>true}, null: false
  end
end

使用 st_point ，而不是 point 作为类型：

add_column :monuments, :grid_ref, :st_point, geographic: true

Postgresql 添加了point类型，因此 postgis 适配器中的类型名称更改为 st_point 。

请参阅 https://github.com/rgeo/activerecord-postgis-adapter#point-and-polygon-types-with-activerecord-42：

在版本 3 之前，支持点和面类型。在 ActiveRecord 4.2，Postgresql 适配器增加了对本机的支持 Postgresql 点和多边形类型，与此适配器的冲突同名的类型。PostGIS 点类型必须引用为 st_point，并且 PostGIS 面类型必须引用为 st_polygon。

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