Question

使用Sequel，在插入行之前很容易应用函数：

the_geom_nosrid = Sequel.function :ST_GeomFromText, params[:the_geom]
the_geom_4326   = Sequel.function :ST_SetSRID,      the_geom_nosrid,  4326
the_geom_900913 = Sequel.function :ST_Transform,    the_geom_4326,    900913

DB[:drawings].returning(:id).insert the_geom: the_geom_900913

这将导致像

这样的查询

INSERT INTO drawings(the_geom) VALUES (ST_Transform(ST_SetSRID(ST_GeomFromText(...), 4326), 900913))

当我使用ActiveRecord插入时，如何应用SQL函数？这不起作用：

class Drawing < ActiveRecord::Base
  before_create do
    the_geom_nosrid = Arel::Nodes::NamedFunction.new('ST_GeomFromText', [the_geom])
    the_geom_4326 = Arel::Nodes::NamedFunction.new('ST_SetSRID', [the_geom_nosrid, 4326])
    the_geom_900913 = Arel::Nodes::NamedFunction.new('ST_Transform', [the_geom_4326, 900913])

    # doesn't work: `Type Error: can't cast Arel::Nodes::NamedFunction to `
    # self.the_geom = the_geom_900913

    # doesn't work: tries to insert the text "ST_Transform(ST_SetSR..." into a geometry column
    # self.the_geom = Arel.sql(the_geom_900913.to_sql)
  end
end

Answer 1

解决了惊人的scuttle.io：

Drawing.create(
  :the_geom => Arel::Nodes::NamedFunction.new(
    'ST_Transform', [
      Arel::Nodes::NamedFunction.new(
        'ST_SetSRID', [
          Arel::Nodes::NamedFunction.new('ST_GeomFromText', ['foobar']), 4326
        ]
      ), 900913
    ]
  )
)

使用ActiveRecord插入时如何使用SQL函数？

1 个答案: