Class: RGeo::CoordSys::SRSDatabase::ActiveRecordTable

Inherits:
Object
  • Object
show all
Defined in:
lib/rgeo/coord_sys/srs_database/active_record_table.rb

Overview

A spatial reference database implementation that uses ActiveRecord to access a spatial reference table provided by a spatial database implementation. You can use this class to obtain coordinate system information from your installation of, e.g. PostGIS.

Constant Summary collapse

@@class_counter =
0

Instance Method Summary collapse

Constructor Details

#initialize(opts_ = {}) ⇒ ActiveRecordTable

Create a new ActiveRecord-backed database connection.

Options include:

:ar_class

An ActiveRecord class to use. You may provide this if you already have an ActiveRecord class that accesses the table. If not provided, an ActiveRecord class will be generated for you, using the :ar_base_class, :database_config, and :table_name options.

:ar_base_class

Specify an ActiveRecord base class to use when generating an ActiveRecord class. Default is ::ActiveRecord::Base. You may want to use this if you have a base class already that specifies an existing database connection and/or other class-scope options.

:database_config

If provided, establish_connection will be called on the generated ActiveRecord class, with the given value.

:table_name

The table name for the new ActiveRecord class. Defaults to the value spatial_ref_sys, which is the OGC-specified name for this table.

:srid_column

The name of the SRID column. Defaults to “srid”, which is the OGC-specified name for this column.

:auth_name_column

The name of the authority name column. On an OGC-compliant database, this column should be named “auth_name”. However, the default is set to nil; you should set this option explicitly if you want to read the authority name.

:auth_srid_column

The name of the authority srid column. On an OGC-compliant database, this column should be named “auth_srid”. However, the default is set to nil; you should set this option explicitly if you want to read the authority's srid.

:name_column

The name of the coordinate system name column. This column is not part of the OGC spec, but it is included in some spatial database implementations. Default is nil.

:description_column

The name of the coordinate system description column. This column is not part of the OGC spec, but may be included in some spatial database implementations. Default is nil.

:srtext_column

The name of the spatial reference WKT column. On an OGC-compliant database, this column should be named “srtext”. However, not all databases include this column, so the default is set to nil; you should set this option explicitly if you want to read the OGC coordinate system specification.

:proj4text_column

The name of the Proj4 format projection spec column. This column is not part of the OGC spec, but may be included in some spatial database implementations. Default is nil.

:cache

If set to true, entries are cached when first retrieved, so subsequent requests do not have to make a database round trip. Default is false.

Some option settings may be provided by the ActiveRecord connection adapter, if the ActiveRecord class's connection uses an adapter that is RGeo-savvy. The “postgis” and “spatialite” adapters are such adapters. They automatically provide the :table_name and all the relevant column settings for the database-provided spatial reference table as defaults. However, you can still override those settings if you want to use a custom table.


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# File 'lib/rgeo/coord_sys/srs_database/active_record_table.rb', line 122

def initialize(opts_={})
  @cache = opts_[:cache] ? {} : nil
  @ar_class = opts_[:ar_class]
  unless @ar_class
    ar_base_class_ = opts_[:ar_base_class] || ::ActiveRecord::Base
    @ar_class = ::Class.new(ar_base_class_)
    self.class.const_set("Klass#{@@class_counter}", @ar_class)
    @@class_counter += 1
    if opts_[:database_config]
      @ar_class.class_eval do
        establish_connection(opts_[:database_config])
      end
    end
  end
  connection_ = @ar_class.connection
  if connection_.respond_to?(:srs_database_columns)
    opts_ = connection_.srs_database_columns.merge(opts_)
  end
  unless opts_[:ar_class]
    @ar_class.class_eval do
      self.table_name = opts_[:table_name] || 'spatial_ref_sys'
    end
  end
  @srid_column = opts_[:srid_column] || 'srid'
  @auth_name_column = opts_[:auth_name_column]
  @auth_srid_column = opts_[:auth_srid_column]
  @name_column = opts_[:name_column]
  @description_column = opts_[:description_column]
  @srtext_column = opts_[:srtext_column]
  @proj4text_column = opts_[:proj4text_column]
end

Instance Method Details

#clear_cacheObject

Clears the cache if a cache is active.


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# File 'lib/rgeo/coord_sys/srs_database/active_record_table.rb', line 184

def clear_cache
  @cache.clear if @cache
end

#get(ident_) ⇒ Object

Retrieve an Entry given an integer SRID.


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# File 'lib/rgeo/coord_sys/srs_database/active_record_table.rb', line 157

def get(ident_)
  ident_ = ident_.to_i
  return @cache[ident_] if @cache && @cache.include?(ident_)
  obj_ = @ar_class.where(@srid_column => ident_).first
  unless obj_
    @cache[ident_] = nil if @cache
    return nil
  end
  auth_name_ = @auth_name_column ? obj_[@auth_name_column] : nil
  auth_srid_ = @auth_srid_column ? obj_[@auth_srid_column] : nil
  name_ = @name_column ? obj_[@name_column] : nil
  description_ = @description_column ? obj_[@description_column] : nil
  coord_sys_ = proj4_ = nil
  if @srtext_column
    coord_sys_ = CS.create_from_wkt(obj_[@srtext_column]) rescue nil
  end
  if @proj4text_column && Proj4.supported?
    proj4_ = Proj4.create(obj_[@proj4text_column].strip) rescue nil
  end
  result_ = Entry.new(ident_, :authority => auth_name_, :authority_code => auth_srid_, :name => name_, :description => description_, :coord_sys => coord_sys_, :proj4 => proj4_)
  @cache[ident_] = result_ if @cache
  result_
end