Module: ActiveRecord::AttributeMethods

Defined in:
lib/active_record/attribute_methods.rb

Overview

:nodoc:

Defined Under Namespace

Modules: ClassMethods

Constant Summary collapse

DEFAULT_SUFFIXES = 
%w(= ? _before_type_cast)
ATTRIBUTE_TYPES_CACHED_BY_DEFAULT = 
[:datetime, :timestamp, :time, :date]

Class Method Summary collapse

Instance Method Summary collapse

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(method_id, *args, &block) ⇒ Object

Allows access to the object attributes, which are held in the @attributes hash, as though they were first-class methods. So a Person class with a name attribute can use Person#name and Person#name= and never directly use the attributes hash – except for multiple assigns with ActiveRecord#attributes=. A Milestone class can also ask Milestone#completed? to test that the completed attribute is not nil or 0.

It’s also possible to instantiate related objects, so a Client class belonging to the clients table with a master_id foreign key can instantiate master through Client#master.



181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
 
# File 'lib/active_record/attribute_methods.rb', line 181

def method_missing(method_id, *args, &block)
  method_name = method_id.to_s

  # If we haven't generated any methods yet, generate them, then
  # see if we've created the method we're looking for.
  if !self.class.generated_methods?
    self.class.define_attribute_methods
    if self.class.generated_methods.include?(method_name)
      return self.send(method_id, *args, &block)
    end
  end
  
  if self.class.primary_key.to_s == method_name
    id
  elsif md = self.class.match_attribute_method?(method_name)
    attribute_name, method_type = md.pre_match, md.to_s
    if @attributes.include?(attribute_name)
      __send__("attribute#{method_type}", attribute_name, *args, &block)
    else
      super
    end
  elsif @attributes.include?(method_name)
    read_attribute(method_name)
  else
    super
  end
end

Class Method Details

.included(base) ⇒ Object 



6
7
8
9
10
11
 
# File 'lib/active_record/attribute_methods.rb', line 6

def self.included(base)
  base.extend ClassMethods
  base.attribute_method_suffix *DEFAULT_SUFFIXES
  base.cattr_accessor :attribute_types_cached_by_default, :instance_writer => false
  base.attribute_types_cached_by_default = ATTRIBUTE_TYPES_CACHED_BY_DEFAULT
end

Instance Method Details

#query_attribute(attr_name) ⇒ Object 



263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
 
# File 'lib/active_record/attribute_methods.rb', line 263

def query_attribute(attr_name)
  unless value = read_attribute(attr_name)
    false
  else
    column = self.class.columns_hash[attr_name]
    if column.nil?
      if Numeric === value || value !~ /[^0-9]/
        !value.to_i.zero?
      else
        !value.blank?
      end
    elsif column.number?
      !value.zero?
    else
      !value.blank?
    end
  end
end

#read_attribute(attr_name) ⇒ Object

Returns the value of the attribute identified by attr_name after it has been typecast (for example, “2004-12-12” in a data column is cast to a date object, like Date.new(2004, 12, 12)).



211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
 
# File 'lib/active_record/attribute_methods.rb', line 211

def read_attribute(attr_name)
  attr_name = attr_name.to_s
  if !(value = @attributes[attr_name]).nil?
    if column = column_for_attribute(attr_name)
      if unserializable_attribute?(attr_name, column)
        unserialize_attribute(attr_name)
      else
        column.type_cast(value)
      end
    else
      value
    end
  else
    nil
  end
end

#read_attribute_before_type_cast(attr_name) ⇒ Object 



228
229
230
 
# File 'lib/active_record/attribute_methods.rb', line 228

def read_attribute_before_type_cast(attr_name)
  @attributes[attr_name]
end

#respond_to?(method, include_priv = false) ⇒ Boolean

Returns:

  • (Boolean) 


285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
 
# File 'lib/active_record/attribute_methods.rb', line 285

def respond_to?(method, include_priv = false)
  method_name = method.to_s
  if super
    return true
  elsif !self.class.generated_methods?
    self.class.define_attribute_methods
    if self.class.generated_methods.include?(method_name)
      return true
    end
  end
    
  if @attributes.nil?
    return super
  elsif @attributes.include?(method_name)
    return true
  elsif md = self.class.match_attribute_method?(method_name)
    return true if @attributes.include?(md.pre_match)
  end
  super
end

#respond_to_without_attributes? ⇒ Object

A Person object with a name attribute can ask person.respond_to?(“name”), person.respond_to?(“name=”), and person.respond_to?(“name?”) which will all return true.



284
 
# File 'lib/active_record/attribute_methods.rb', line 284

alias :respond_to_without_attributes? :respond_to?

#unserializable_attribute?(attr_name, column) ⇒ Boolean

Returns true if the attribute is of a text column and marked for serialization.

Returns:

  • (Boolean) 


233
234
235
 
# File 'lib/active_record/attribute_methods.rb', line 233

def unserializable_attribute?(attr_name, column)
  column.text? && self.class.serialized_attributes[attr_name]
end

#unserialize_attribute(attr_name) ⇒ Object

Returns the unserialized object of the attribute.



238
239
240
241
242
243
244
245
246
247
 
# File 'lib/active_record/attribute_methods.rb', line 238

def unserialize_attribute(attr_name)
  unserialized_object = object_from_yaml(@attributes[attr_name])

  if unserialized_object.is_a?(self.class.serialized_attributes[attr_name]) || unserialized_object.nil?
    @attributes.frozen? ? unserialized_object : @attributes[attr_name] = unserialized_object
  else
    raise SerializationTypeMismatch,
      "#{attr_name} was supposed to be a #{self.class.serialized_attributes[attr_name]}, but was a #{unserialized_object.class.to_s}"
  end
end

#write_attribute(attr_name, value) ⇒ Object

Updates the attribute identified by attr_name with the specified value. Empty strings for fixnum and float columns are turned into nil.



252
253
254
255
256
257
258
259
260
 
# File 'lib/active_record/attribute_methods.rb', line 252

def write_attribute(attr_name, value)
  attr_name = attr_name.to_s
  @attributes_cache.delete(attr_name)
  if (column = column_for_attribute(attr_name)) && column.number?
    @attributes[attr_name] = convert_number_column_value(value)
  else
    @attributes[attr_name] = value
  end
end