ArgumentError: wrong number of arguments (1 for 0)
from /Users/Castillo/Desktop/gainer/app/models/status.rb:13:in `update_remaining_nutrients'
from /usr/local/rvm/gems/ruby-1.9.3-p392/gems/activerecord-3.2.11/lib/active_record/associations/collection_association.rb:507:in `block in callback'
from /usr/local/rvm/gems/ruby-1.9.3-p392/gems/activerecord-3.2.11/lib/active_record/associations/collection_association.rb:504:in `each'
from /usr/local/rvm/gems/ruby-1.9.3-p392/gems/activerecord-3.2.11/lib/active_record/associations/collection_association.rb:504:in `callback'
from /usr/local/rvm/gems/ruby-1.9.3-p392/gems/activerecord-3.2.11/lib/active_record/associations/collection_association.rb:352:in `add_to_target'
from /usr/local/rvm/gems/ruby-1.9.3-p392/gems/activerecord-3.2.11/lib/active_record/associations/collection_association.rb:495:in `block in concat_records'
from /usr/local/rvm/gems/ruby-1.9.3-p392/gems/activerecord-3.2.11/lib/active_record/associations/collection_association.rb:493:in `each'
from /usr/local/rvm/gems/ruby-1.9.3-p392/gems/activerecord-3.2.11/lib/active_record/associations/collection_association.rb:493:in `concat_records'
from /usr/local/rvm/gems/ruby-1.9.3-p392/gems/activerecord-3.2.11/lib/active_record/associations/collection_association.rb:134:in `block in concat'
from /usr/local/rvm/gems/ruby-1.9.3-p392/gems/activerecord-3.2.11/lib/active_record/associations/collection_association.rb:149:in `block in transaction'
from /usr/local/rvm/gems/ruby-1.9.3-p392/gems/activerecord-3.2.11/lib/active_record/connection_adapters/abstract/database_statements.rb:192:in `transaction'
from /usr/local/rvm/gems/ruby-1.9.3-p392/gems/activerecord-3.2.11/lib/active_record/transactions.rb:208:in `transaction'
from /usr/local/rvm/gems/ruby-1.9.3-p392/gems/activerecord-3.2.11/lib/active_record/associations/collection_association.rb:148:in `transaction'
from /usr/local/rvm/gems/ruby-1.9.3-p392/gems/activerecord-3.2.11/lib/active_record/associations/collection_association.rb:134:in `concat'
from /usr/local/rvm/gems/ruby-1.9.3-p392/gems/activerecord-3.2.11/lib/active_record/associations/collection_proxy.rb:116:in `<<'
from /Users/Castillo/Desktop/gainer/app/models/user.rb:65:in `eat'
from (irb):31
from /usr/local/rvm/gems/ruby-1.9.3-p392/gems/railties-3.2.11/lib/rails/commands/console.rb:47:in `start'
from /usr/local/rvm/gems/ruby-1.9.3-p392/gems/railties-3.2.11/lib/rails/commands/console.rb:8:in `start'
from /usr/local/rvm/gems/ruby-1.9.3-p392/gems/railties-3.2.11/lib/rails/commands.rb:41:in `<top (required)>'
每当用户“吃”一顿饭时，我都想在status.rb上调用update_remaining_ Nutritions方法。当我调用User.first.eat（Meal.first）时，我收到ArgumentError。不知道为什么，因为我没有传递after_add方法任何参数？
user.rb
class User < ActiveRecord::Base
has_many :meals
has_many :statuses
def eat(meal)
statuses.last.meals<<meal
end
end
status.rb
class Status < ActiveRecord::Base
attr_accessible :remaining_calories, :remaining_carbs, :remaining_protein, :weight, :user_id
belongs_to :user
has_many :meals, after_add: :update_remaining_nutrients
after_save :update_users_weight , :if => Proc.new {|a| a.weight_changed?}
def update_users_weight
self.user.weight.update_attributes(weight: self.weight)
end
def update_remaining_nutrients
puts "It Works!!!!!"
end
end
饭菜
class Meal < ActiveRecord::Base
attr_accessible :name, :description, :clean_up, :homemade, :prep_time, :user_id, :status_id
belongs_to :user
belongs_to :status
has_many :ingredient_meals
has_many :ingredients, :through => :ingredient_meals
end
如果您查看文档的“关联回调”部分，则会看到以下示例：
class Project
has_and_belongs_to_many :developers, after_add: :evaluate_velocity
def evaluate_velocity(developer)
...
end
end
那不是has_many你所拥有的关系，但是它已经足够亲密了。如果查看该evaluate_velocity方法，您会看到有developer问题的:after_add回调作为回调传递给参数。您将收到一个ArgumentError，该错误是关于您update_remaining_nutrients在不希望使用任何参数的情况下被调用的，并且与示例中所建议的匹配。
试试这个：
def update_remaining_nutrients(meal)
# Do interesting things with `meal` in here...
end
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我来说两句