Add extensive documentation to the ActiveRecord::AbstractAdapter. #2250

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@2371 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb

@@ -1,4 +1,5 @@
 module ActiveRecord
+  # The root class of all active record objects.
   class Base
     class ConnectionSpecification #:nodoc:
       attr_reader :config, :adapter_method

activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb

@@ -1,11 +1,12 @@
 module ActiveRecord
   module ConnectionAdapters # :nodoc:
-    # TODO: Document me!
     module DatabaseStatements
-      # Returns an array of record hashes with the column names as a keys and fields as values.
+      # Returns an array of record hashes with the column names as keys and
+      # column values as values.
       def select_all(sql, name = nil) end
 
-      # Returns a record hash with the column names as a keys and fields as values.
+      # Returns a record hash with the column names as keys and column values
+      # as values.
       def select_one(sql, name = nil) end
 
       # Returns a single value from a record
@@ -21,8 +22,11 @@ def select_values(sql, name = nil)
         result.map{ |v| v.values.first }
       end
 
-      # Executes the statement
-      def execute(sql, name = nil) end
+      # Executes the SQL statement in the context of this connection.
+      # This abstract method raises a NotImplementedError.
+      def execute(sql, name = nil)
+        raise NotImplementedError, "execute is an abstract method"
+      end
 
       # Returns the last auto-generated ID from the affected table.
       def insert(sql, name = nil, pk = nil, id_value = nil, sequence_name = nil) end
@@ -54,16 +58,23 @@ def begin_db_transaction()    end
       # Commits the transaction (and turns on auto-committing).
       def commit_db_transaction()   end
 
-      # Rolls back the transaction (and turns on auto-committing). Must be done if the transaction block
-      # raises an exception or returns false.
+      # Rolls back the transaction (and turns on auto-committing). Must be
+      # done if the transaction block raises an exception or returns false.
       def rollback_db_transaction() end
 
-      def add_limit!(sql, options) #:nodoc:
+      # Alias for #add_limit_offset!.
+      def add_limit!(sql, options)
         return unless options
         add_limit_offset!(sql, options)
       end
 
-      def add_limit_offset!(sql, options) #:nodoc:
+      # Appends +LIMIT+ and +OFFSET+ options to a SQL statement.
+      # This method *modifies* the +sql+ parameter.
+      # ===== Examples
+      #  add_limit_offset!('SELECT * FROM suppliers', {:limit => 10, :offset => 50})
+      # generates
+      #  SELECT * FROM suppliers LIMIT 10 OFFSET 50
+      def add_limit_offset!(sql, options)
         return if options[:limit].nil?
         sql << " LIMIT #{options[:limit]}"
         sql << " OFFSET #{options[:offset]}" if options.has_key?(:offset) and !options[:offset].nil?

activerecord/lib/active_record/connection_adapters/abstract/quoting.rb

@@ -1,7 +1,8 @@
 module ActiveRecord
   module ConnectionAdapters # :nodoc:
-    # TODO: Document me!
     module Quoting
+      # Quotes the column value to help prevent
+      # {SQL injection attacks}[http://en.wikipedia.org/wiki/SQL_injection].
       def quote(value, column = nil)
         case value
           when String
@@ -22,10 +23,14 @@ def quote(value, column = nil)
         end
       end
 
+      # Quotes a string, escaping any ' (single quote) and \ (backslash)
+      # characters.
       def quote_string(s)
         s.gsub(/\\/, '\&\&').gsub(/'/, "''") # ' (for ruby-mode)
       end
 
+      # Returns a quoted form of the column name.  This is highly adapter
+      # specific.
       def quote_column_name(name)
         name
       end

activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb

@@ -1,18 +1,23 @@
 module ActiveRecord
   module ConnectionAdapters #:nodoc:
-    class Column #:nodoc:
+    # An abstract definition of a column in a table.
+    class Column
       attr_reader :name, :default, :type, :limit, :null
-      # The name should contain the name of the column, such as "name" in "name varchar(250)"
-      # The default should contain the type-casted default of the column, such as 1 in "count int(11) DEFAULT 1"
-      # The type parameter should either contain :integer, :float, :datetime, :date, :text, or :string
-      # The sql_type is just used for extracting the limit, such as 10 in "varchar(10)"
+
+      # Instantiates a new column in the table.
+      #
+      # +name+ is the column's name, as in <tt><b>supplier_id</b> int(11)</tt>.
+      # +default+ is the type-casted default value, such as <tt>sales_stage varchar(20) default <b>'new'</b></tt>.
+      # +sql_type+ is only used to extract the column's length, if necessary.  For example, <tt>company_name varchar(<b>60</b>)</tt>.
+      # +null+ determines if this column allows +NULL+ values.
       def initialize(name, default, sql_type = nil, null = true)
         @name, @type, @null = name, simplified_type(sql_type), null
         # have to do this one separately because type_cast depends on #type
         @default = type_cast(default)
         @limit = extract_limit(sql_type) unless sql_type.nil?
       end
 
+      # Returns the Ruby class that corresponds to the abstract data type.
       def klass
         case type
           when :integer       then Fixnum
@@ -27,6 +32,7 @@ def klass
         end
       end
 
+      # Casts value (which is a String) to an appropriate instance.
       def type_cast(value)
         if value.nil? then return nil end
         case type
@@ -44,14 +50,20 @@ def type_cast(value)
         end
       end
 
+      # Returns the human name of the column name.
+      #
+      # ===== Examples
+      #  Column.new('sales_stage', ...).human_name #=> 'Sales stage'
       def human_name
         Base.human_attribute_name(@name)
       end
 
+      # Used to convert from Strings to BLOBs
       def string_to_binary(value)
         value
       end
 
+      # Used to convert from BLOBs to Strings
       def binary_to_string(value)
         value
       end
@@ -108,7 +120,7 @@ def simplified_type(field_type)
           end
         end
     end
-    
+
     class IndexDefinition < Struct.new(:table, :name, :unique, :columns) #:nodoc:
     end
 
@@ -130,22 +142,58 @@ def add_column_options!(sql, options)
         end
     end
 
-    class TableDefinition #:nodoc:
+    # Represents a SQL table in an abstract way.
+    # Columns are stored as ColumnDefinition in the #columns attribute.
+    class TableDefinition
       attr_accessor :columns
 
       def initialize(base)
         @columns = []
         @base = base
       end
 
+      # Appends a primary key definition to the table definition.
+      # Can be called multiple times, but this is probably not a good idea.
       def primary_key(name)
         column(name, native[:primary_key])
       end
-
+
+      # Returns a ColumnDefinition for the column with name +name+.
       def [](name)
         @columns.find {|column| column.name == name}
       end
 
+      # Instantiates a new column for the table.
+      # The +type+ parameter must be one of the following values:
+      # <tt>:primary_key</tt>, <tt>:string</tt>, <tt>:text</tt>,
+      # <tt>:integer</tt>, <tt>:float</tt>, <tt>:datetime</tt>,
+      # <tt>:timestamp</tt>, <tt>:time</tt>, <tt>:date</tt>,
+      # <tt>:binary</tt>, <tt>:boolean</tt>.
+      #
+      # Available options are (none of these exists by default):
+      # * <tt>:limit</tt>:
+      #   Requests a maximum column length (<tt>:string</tt>, <tt>:text</tt>,
+      #   <tt>:binary</tt> or <tt>:integer</tt> columns only)
+      # * <tt>:default</tt>:
+      #   The column's default value.  You cannot explicitely set the default
+      #   value to +NULL+.  Simply leave off this option if you want a +NULL+
+      #   default value.
+      # * <tt>:null</tt>:
+      #   Allows or disallows +NULL+ values in the column.  This option could
+      #   have been named <tt>:null_allowed</tt>.
+      #
+      # This method returns <tt>self</tt>.
+      #
+      # ===== Examples
+      #  # Assuming def is an instance of TableDefinition
+      #  def.column(:granted, :boolean)
+      #    #=> granted BOOLEAN
+      #
+      #  def.column(:picture, :binary, :limit => 2.megabytes)
+      #    #=> picture BLOB(2097152)
+      #
+      #  def.column(:sales_stage, :string, :limit => 20, :default => 'new', :null => false)
+      #    #=> sales_stage VARCHAR(20) DEFAULT 'new' NOT NULL
       def column(name, type, options = {})
         column = self[name] || ColumnDefinition.new(@base, name, type)
         column.limit = options[:limit] || native[type.to_sym][:limit] if options[:limit] or native[type.to_sym]
@@ -155,6 +203,9 @@ def column(name, type, options = {})
         self
       end
 
+      # Returns a String whose contents are the column definitions
+      # concatenated together.  This string can then be pre and appended to
+      # to generate the final SQL to create the table.
       def to_sql
         @columns * ', '
       end