Top Level Namespace

Defined Under Namespace

Modules: Automodel

Instance Method Summary collapse

Instance Method Details

#automodel(spec) ⇒ ActiveRecord::Base

The main (really only) entrypoint for the automodel-sqlserver gem. This is the method the end-user calls to trigger a database scrape and model generation.

Parameters:

  • spec (Symbol, String, Hash) —

    The Symbol/String/Hash to pass through to the ActiveRecord connection resolver, as detailed in ActiveRecord::ConnectionHandling#establish_connection. Whether the given “spec” value is a Hash or is a Symbol/String to run through the ActiveRecord resolver, the resulting Hash may include the following options (in addition to the actual connection parameters).

Options Hash (spec):

  • :subschema (String) —

    The name of an additional namespace with which tables in the target database are prefixed. Intended for use with SQL Server, where a table's fully-qualified name may have an additional level of namespacing between the database name and the base table name (e.g. database.dbo.table, in which case the subschema would be "dbo").

  • :namespace (String) —

    A String representing the desired namespace for the generated model classes (e.g. "NewDB" or "WeirdDB::Models"). If not given, the generated models will fall under Kernel so they are always available without namespacing, like standard user-defined model classes.

Returns:

  • (ActiveRecord::Base) —

    The returned value is an instance of an ActiveRecord::Base subclass. This is the class that serves as superclass to all of the generated model classes, so that a list of all models can be easily compiled by calling #subclasses on this value.

Raises:

  • (Automodel::ModelNameCollisionError) 


40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
 
# File 'lib/automodel.rb', line 40

def automodel(spec)
  ## Build out a connection spec Hash from the given value.
  ##
  resolver = ActiveRecord::ConnectionAdapters::ConnectionSpecification::Resolver
  connection_spec = resolver.new(ActiveRecord::Base.configurations).resolve(spec).symbolize_keys

  ## We need a base class for all of the models we're about to create, but don't want to pollute
  ## ActiveRecord::Base's own connection pool, so we'll need a subclass. This will serve as both
  ## our base class for new models and as the connection pool handler. We're defining it with names
  ## that reflect both uses just to keep the code more legible.
  ##
  connection_handler_name = "CH_#{SecureRandom.uuid.delete('-')}"
  base_class_for_new_models = connection_handler = Class.new(ActiveRecord::Base)
  Automodel::Helpers.register_class(connection_handler, as: connection_handler_name,
                                                        within: :'Automodel::Connectors')

  ## Establish a connection with the given params.
  ##
  connection_handler.establish_connection(connection_spec)

  ## Map out the table structures.
  ##
  tables = Automodel::Helpers.map_tables(connection_handler, subschema: connection_spec[:subschema])

  ## Safeguard against class name collisions.
  ##
  defined_names = Array((connection_spec[:namespace] || :Kernel).to_s.safe_constantize&.constants)
  potential_names = tables.map { |table| table[:model_name].to_sym }
  name_collisions = defined_names & potential_names
  if name_collisions.present?
    connection_handler.connection_pool.disconnect!
    Automodel::Connectors.send(:remove_const, connection_handler_name)
    raise Automodel::NameCollisionError, name_collisions
  end

  ## Define the table models.
  ##
  tables.each do |table|
    table[:model] = Class.new(base_class_for_new_models) do
      ## We can't assume table properties confom to any standard.
      ##
      self.table_name = table[:name]
      self.primary_key = table[:primary_key]

      ## Don't allow `#find` for tables with a composite primary key.
      ##
      def find(*args)
        raise Automodel::FindOnCompoundPrimaryKeyError if table[:composite_primary_key]
        super
      end

      ## Create railsy column name aliases whenever possible.
      ##
      table[:columns].each do |column|
        railsy_name = Automodel::Helpers.railsy_column_name(column)
        unless table[:column_aliases].key? railsy_name
          table[:column_aliases][railsy_name] = column
          alias_attribute(railsy_name, column.name)
        end
      end
    end

    ## Register the model class.
    ##
    Automodel::Helpers.register_class(table[:model], as: table[:model_name],
                                                     within: connection_spec[:namespace])
  end

  ## With all models registered, we can safely declare relationships.
  ##
  tables.map { |table| table[:foreign_keys] }.flatten.each do |fk|
    from_table = tables.find { |table| table[:base_name] == fk.from_table.delete('"') }
    next unless from_table.present?

    to_table = tables.find { |table| table[:base_name] == fk.to_table.delete('"') }
    next unless to_table.present?

    association_setup = <<~END_OF_HEREDOC
      belongs_to #{to_table[:base_name].to_sym.inspect},
                 class_name: #{to_table[:model].to_s.inspect},
                 primary_key: #{fk.options[:primary_key].to_sym.inspect},
                 foreign_key: #{fk.options[:column].to_sym.inspect}

      alias #{to_table[:model_name].underscore.to_sym.inspect} #{to_table[:base_name].to_sym.inspect}
    END_OF_HEREDOC
    from_table[:model].class_eval(association_setup, __FILE__, __LINE__)
  end

  ## There's no obvious value we can return that would be of any use, except maybe the base class,
  ## in case the end user wants to procure a list of all the models (via `#subclasses`).
  ##
  base_class_for_new_models
end