Ruby on Rails 关于object的方法create 和 new 的区别

From the ActiveRecord::Base documentation:

create(attributes = nil) {|object| ...}

Creates an object (or multiple objects) and saves it to the database, if validations pass. The resulting object is returned whether the object was saved successfully to the database or not.

new(attributes = nil) {|self if block_given?| ...}

New objects can be instantiated as either empty (pass no construction parameter) or pre-set with attributes but not yet saved (pass a hash with key names matching the associated table column names). In both instances, valid attribute keys are determined by the column names of the associated table — hence you can‘t have attributes that aren‘t part of the table columns.

So create instantiates the new object, validates it, and then saves it to the database. And new only creates the local object but does not attempt to validate or save it to the DB.

create = "new object" + ”validates“ + ”save to db“

new = “new object”

在create的内部方法中，先调用new ，再调用save：new + save = create

def create(attributes = nil, options = {}, &block)
    if attributes.is_a?(Array)
      attributes.collect { |attr| create(attr, options, &block) }
    else
      object = new(attributes, options, &block)
      object.save
      object
    end
  end

转载自：

http://stackoverflow.com/questions/2472393/rails-new-vs-create

http://stackoverflow.com/questions/9791386/differences-between-new-save-and-create