data_objects_schema.rb

# DataObjects::Schema::
#                      Database
#                      Table
#
#                      Column::
#                              String  < Column
#                              Numeric < Column
#                              Integer < Numeric
#                              Float   < Numeric
#                              Decimal < Numeric
#                              ...
#
#                      Index
#                      UniqueIndex < Index
#                      PrimaryKey  < UniqueIndex
#                      ForeignKey
#                      Reference
#
#                      OrderedSet
#                      Columns       (has-a OrderedSet)
#                      Indexes       (has-a OrderedSet)
#                      UniqueIndexes (has-a OrderedSet)
#                      ForeignKeys   (has-a OrderedSet)

uri = Addressable::URI.parse('mysql://localhost/dm_core_test')

database = DataObjects::Schema.load(uri)

database.name                  # => "dm_core_test"
database.uri                   # => uri
database.tables                # => Tables.new([ Table1, Table2, ... ])

database.tables.each do |table|

  # Table API
  table                        # => Table.new('customers', [ Column1, Column2, ... ], :indexes => indexes)
  table.name                   # => "customers"
  table.to_ddl                 # => CREATE TABLE customers (id INT(10) UNSIGNED NOT NULL, name CHAR(10) NOT NULL DEFAULT 'a', PRIMARY KEY(id))

  # Column API
  table.columns                # => Columns.new([ Column1, Column2, ... ])
  table.columns.to_ddl         # => "id INT(10) UNSIGNED NOT NULL, name CHAR(10) NOT NULL DEFAULT 'a'"

  table.each do |column|
    column                     # => Column::String.new('name', :length => 0..10)
    column.name                # => "name"
    column.required?           # => true
    column.default             # => "a"
    column.to_ddl              # => "name CHAR(10) NOT NULL DEFAULT 'a'"

    # NOTE: Column subclasses will be able to add extra accessors for type
    #       specific data. For example Column::String may define #length,
    #       and Column::Decimal may define #precision and #scale
  end

  # Primary Key API
  table.primary_key            # => PrimaryKey.new(name, [ Column1, Column2, ... ])
  table.primary_key.columns    # => Columns.new([ Column1, Column2, ... ])
  table.primary_key.unique?    # => true
  table.primary_key.to_ddl     # => "PRIMARY KEY(id)"

  # Index API
  table.indexes                # => Indexes.new([ Index1, Index2, ... ])
  table.indexes.to_ddl         # => "KEY index_name1 (column_name1), KEY index_name2 (column_name2)"

  table.indexes.each do |index|
    index                      # => Index.new('index_name', [ Column1, Column2, ... ])
    index.name                 # => "index_name"
    index.unique?              # => false
    index.columns              # => Columns.new([ Column1, Column2, ... ])
    index.to_ddl               # => "KEY index_name (column_name)"
  end

  # Unique Index API
  table.unique_indexes         # => UniqueIndexes.new([ UniqueIndex1, UniqueIndex1, ... ])
  table.unique_indexes.to_ddl  # => "UNIQUE unique_name1 (column_name1), UNIQUE unique_name2 (column_name2)"

  table.unique_indexes.each do |unique_index|
    unique_index               # => UniqueIndex.new('unique_name', [ Column1, Column2, ... ])
    unique_index.name          # => "unique_name"
    unique_index.unique?       # => true
    unique_index.columns       # => Columns.new([ Column1, Column2, ... ])
    unique_index.to_ddl        # => "UNIQUE unique_name (column_name)"
  end

  # Foreign Key API
  table.foreign_keys           # => ForeignKeys.new([ ForeignKey1, ForeignKey2, ... ])
  table.foreign_keys.to_ddl    # => "FOREIGN KEY (parent_id) REFERENCES parent (id), FOREIGN KEY (other_id) REFERENCES other (id)"

  table.foreign_keys.each do |foreign_key|
    foreign_key                # => ForeignKey.new('foreign_key_name', [ Column1, Column2, ... ], reference, :on_delete => :restrict, :on_update => :restrict)
    foreign_key.name           # => "foreign_key_name"
    foreign_key.columns        # => Columns.new([ Column1, Column2, ... ])
    foreign_key.reference      # => Reference.new(other_table, other_table.primary_key)
    foreign_key.on_delete      # => :restrict
    foreign_key.on_update      # => nil
    foreign_key.to_ddl         # => "FOREIGN KEY foreign_key_name (other_id) REFERENCES others (id)"
  end

end

# NOTES: Table, Index, UniqueIndex, PrimaryKey, ForeignKey and Reference
#        are Enumerable, and delegate #each to #columns