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实例公共方法

alias_attribute(new_name, old_name)

来源：显示 | 在 GitHub 上 

# File activerecord/lib/active_record/attribute_methods.rb, line 53
def alias_attribute(new_name, old_name)
  super

  if @alias_attributes_mass_generated
    ActiveSupport::CodeGenerator.batch(generated_attribute_methods, __FILE__, __LINE__) do |code_generator|
      generate_alias_attribute_methods(code_generator, new_name, old_name)
    end
  end
end

alias_attribute_method_definition(code_generator, pattern, new_name, old_name)

来源：显示 | 在 GitHub 上 

# File activerecord/lib/active_record/attribute_methods.rb, line 85
def alias_attribute_method_definition(code_generator, pattern, new_name, old_name)
  method_name = pattern.method_name(new_name).to_s
  target_name = pattern.method_name(old_name).to_s
  parameters = pattern.parameters
  old_name = old_name.to_s

  method_defined = method_defined?(target_name) || private_method_defined?(target_name)
  manually_defined = method_defined &&
    !self.instance_method(target_name).owner.is_a?(GeneratedAttributeMethods)
  reserved_method_name = ::ActiveRecord::AttributeMethods.dangerous_attribute_methods.include?(target_name)

  if !abstract_class? && !has_attribute?(old_name)
    # We only need to issue this deprecation warning once, so we issue it when defining the original reader method.
    should_warn = target_name == old_name
    if should_warn
      ActiveRecord.deprecator.warn(
        "#{self} model aliases `#{old_name}`, but `#{old_name}` is not an attribute. " \
        "Starting in Rails 7.2, alias_attribute with non-attribute targets will raise. " \
        "Use `alias_method :#{new_name}, :#{old_name}` or define the method manually."
      )
    end
    super
  elsif manually_defined && !reserved_method_name
    aliased_method_redefined_as_well = method_defined_within?(method_name, self)
    return if aliased_method_redefined_as_well

    ActiveRecord.deprecator.warn(
      "#{self} model aliases `#{old_name}` and has a method called `#{target_name}` defined. " \
      "Starting in Rails 7.2 `#{method_name}` will not be calling `#{target_name}` anymore. " \
      "You may want to additionally define `#{method_name}` to preserve the current behavior."
    )
    super
  else
    define_proxy_call(code_generator, method_name, pattern.proxy_target, parameters, old_name,
      namespace: :proxy_alias_attribute
    )
  end
end

attribute_method?(attribute)

如果 attribute 是属性方法且存在表，则返回 true，否则返回 false。

class Person < ActiveRecord::Base
end

Person.attribute_method?('name')   # => true
Person.attribute_method?(:age=)    # => true
Person.attribute_method?(:nothing) # => false

来源：显示 | 在 GitHub 上 

# File activerecord/lib/active_record/attribute_methods.rb, line 219
def attribute_method?(attribute)
  super || (table_exists? && column_names.include?(attribute.to_s.delete_suffix("=")))
end

attribute_names()

如果它不是抽象类且存在表，则返回一个字符串形式的列名数组。否则返回一个空数组。

class Person < ActiveRecord::Base
end

Person.attribute_names
# => ["id", "created_at", "updated_at", "name", "age"]

源：显示 | 在 GitHub 上 

# File activerecord/lib/active_record/attribute_methods.rb, line 231
def attribute_names
  @attribute_names ||= if !abstract_class? && table_exists?
    attribute_types.keys
  else
    []
  end.freeze
end

dangerous_class_method?(method_name)

如果某个类方法已被 Active Record 重新定义，但未被任何祖先重新定义，则该方法“危险”。（因此，“puts”不危险，而“new”则危险。）

源：显示 | 在 GitHub 上 

# File activerecord/lib/active_record/attribute_methods.rb, line 196
def dangerous_class_method?(method_name)
  return true if RESTRICTED_CLASS_METHODS.include?(method_name.to_s)

  if Base.respond_to?(method_name, true)
    if Object.respond_to?(method_name, true)
      Base.method(method_name).owner != Object.method(method_name).owner
    else
      true
    end
  else
    false
  end
end

has_attribute?(attr_name)

如果给定的属性存在，则返回 true，否则返回 false。

class Person < ActiveRecord::Base
  alias_attribute :new_name, :name
end

Person.has_attribute?('name')     # => true
Person.has_attribute?('new_name') # => true
Person.has_attribute?(:age)       # => true
Person.has_attribute?(:nothing)   # => false

源：显示 | 在 GitHub 上 

# File activerecord/lib/active_record/attribute_methods.rb, line 249
def has_attribute?(attr_name)
  attr_name = attr_name.to_s
  attr_name = attribute_aliases[attr_name] || attr_name
  attribute_types.key?(attr_name)
end

instance_method_already_implemented?(method_name)

如果在模型中定义了 Active Record 方法，则引发 ActiveRecord::DangerousAttributeError 异常，否则引发 false。

class Person < ActiveRecord::Base
  def save
    'already defined by Active Record'
  end
end

Person.instance_method_already_implemented?(:save)
# => ActiveRecord::DangerousAttributeError: save is defined by Active Record. Check to make sure that you don't have an attribute or method with the same name.

Person.instance_method_already_implemented?(:name)
# => false

源：显示 | 在 GitHub 上 

# File activerecord/lib/active_record/attribute_methods.rb, line 160
def instance_method_already_implemented?(method_name)
  if dangerous_attribute_method?(method_name)
    raise DangerousAttributeError, "#{method_name} is defined by Active Record. Check to make sure that you don't have an attribute or method with the same name."
  end

  if superclass == Base
    super
  else
    # If ThisClass < ... < SomeSuperClass < ... < Base and SomeSuperClass
    # defines its own attribute method, then we don't want to override that.
    defined = method_defined_within?(method_name, superclass, Base) &&
      ! superclass.instance_method(method_name).owner.is_a?(GeneratedAttributeMethods)
    defined || super
  end
end