我今天正在测试一个片段
unless resource.nil?
resource = resource.becomes(Accounts::Admin)
end
这会引发错误
未定义的方法`成为'为零:NilClass
如果我这样做
unless resource.nil?
a = resource.becomes(Accounts::Admin)
resource = a
end
一切顺利。
如果首先执行=
运算符的右边部分,有什么区别?
编辑:
发生了令人讨厌的事情,if false
下的最后一行正在执行,但是" ALOHA"从未打印过。
<%
puts "AAAA #{resource.inspect}"
if false
puts "ALOHA"
# this line is being executed !
# if I comment it out the BBBB output is correct
resource = nil
end
puts "BBBB #{resource.inspect}"
%>
打印
AAAA用户ID:nil,nome:nil,endereco_id:nil,created_at:nil, updated_at:nil,email:&#34;&#34;
BBBB无
但如果我这样做
<%
res = resource
puts "AAAA #{res.inspect}"
if false
puts "ALOHA"
res = nil
end
puts "BBBB #{res.inspect}"
%>
正确打印
AAAA用户ID:nil,nome:nil,endereco_id:nil,created_at:nil, updated_at:nil,email:&#34;&#34;
BBBB用户名:nil,nome:nil, endereco_id:nil,created_at:nil,updated_at:nil,email:&#34;&#34;
我已经尝试重启服务器了。此代码段位于devise/registrations/new.html.erb
。 resource
变量应该是User
的一个实例,由设计的RegistrationController创建
我已经检查了隐藏字符的文本,我粘贴的片段是正在测试的文件的全文。
这是~/.rvm/gems/ruby-2.3.3@mygem/gems/devise-4.2.0/app/controllers/devise/registrations_controller.rb
class Devise::RegistrationsController < DeviseController
prepend_before_action :require_no_authentication, only: [:new, :create, :cancel]
prepend_before_action :authenticate_scope!, only: [:edit, :update, :destroy]
prepend_before_action :set_minimum_password_length, only: [:new, :edit]
# GET /resource/sign_up
def new
build_resource({})
yield resource if block_given?
respond_with resource
end
# POST /resource
def create
build_resource(sign_up_params)
resource.save
yield resource if block_given?
if resource.persisted?
if resource.active_for_authentication?
set_flash_message! :notice, :signed_up
sign_up(resource_name, resource)
respond_with resource, location: after_sign_up_path_for(resource)
else
set_flash_message! :notice, :"signed_up_but_#{resource.inactive_message}"
expire_data_after_sign_in!
respond_with resource, location: after_inactive_sign_up_path_for(resource)
end
else
clean_up_passwords resource
set_minimum_password_length
respond_with resource
end
end
# GET /resource/edit
def edit
render :edit
end
# PUT /resource
# We need to use a copy of the resource because we don't want to change
# the current user in place.
def update
self.resource = resource_class.to_adapter.get!(send(:"current_#{resource_name}").to_key)
prev_unconfirmed_email = resource.unconfirmed_email if resource.respond_to?(:unconfirmed_email)
resource_updated = update_resource(resource, account_update_params)
yield resource if block_given?
if resource_updated
if is_flashing_format?
flash_key = update_needs_confirmation?(resource, prev_unconfirmed_email) ?
:update_needs_confirmation : :updated
set_flash_message :notice, flash_key
end
bypass_sign_in resource, scope: resource_name
respond_with resource, location: after_update_path_for(resource)
else
clean_up_passwords resource
respond_with resource
end
end
# DELETE /resource
def destroy
resource.destroy
Devise.sign_out_all_scopes ? sign_out : sign_out(resource_name)
set_flash_message! :notice, :destroyed
yield resource if block_given?
respond_with_navigational(resource){ redirect_to after_sign_out_path_for(resource_name) }
end
# GET /resource/cancel
# Forces the session data which is usually expired after sign
# in to be expired now. This is useful if the user wants to
# cancel oauth signing in/up in the middle of the process,
# removing all OAuth session data.
def cancel
expire_data_after_sign_in!
redirect_to new_registration_path(resource_name)
end
protected
def update_needs_confirmation?(resource, previous)
resource.respond_to?(:pending_reconfirmation?) &&
resource.pending_reconfirmation? &&
previous != resource.unconfirmed_email
end
# By default we want to require a password checks on update.
# You can overwrite this method in your own RegistrationsController.
def update_resource(resource, params)
resource.update_with_password(params)
end
# Build a devise resource passing in the session. Useful to move
# temporary session data to the newly created user.
def build_resource(hash=nil)
self.resource = resource_class.new_with_session(hash || {}, session)
end
# Signs in a user on sign up. You can overwrite this method in your own
# RegistrationsController.
def sign_up(resource_name, resource)
sign_in(resource_name, resource)
end
# The path used after sign up. You need to overwrite this method
# in your own RegistrationsController.
def after_sign_up_path_for(resource)
after_sign_in_path_for(resource)
end
# The path used after sign up for inactive accounts. You need to overwrite
# this method in your own RegistrationsController.
def after_inactive_sign_up_path_for(resource)
scope = Devise::Mapping.find_scope!(resource)
router_name = Devise.mappings[scope].router_name
context = router_name ? send(router_name) : self
context.respond_to?(:root_path) ? context.root_path : "/"
end
# The default url to be used after updating a resource. You need to overwrite
# this method in your own RegistrationsController.
def after_update_path_for(resource)
signed_in_root_path(resource)
end
# Authenticates the current scope and gets the current resource from the session.
def authenticate_scope!
send(:"authenticate_#{resource_name}!", force: true)
self.resource = send(:"current_#{resource_name}")
end
def sign_up_params
devise_parameter_sanitizer.sanitize(:sign_up)
end
def account_update_params
devise_parameter_sanitizer.sanitize(:account_update)
end
def translation_scope
'devise.registrations'
end
end
红宝石2.3.3 铁轨(4.2.7.1) 设计(4.2.0)
答案 0 :(得分:5)
看看这个红宝石片段:
if true
foo = "hello"
end
puts foo
#=> hello
这一个:
if false
foo = "hello"
end
puts foo
#=> nil
在许多语言中,if语句都有自己的范围,但在ruby中它们共享周围函数的范围。这意味着在if语句中声明的变量可以在if语句之外访问。
这里的问题是变量是在编译时声明的,之后ruby知道if语句是true
还是false
。所以在ruby中,所有局部变量都被声明并初始化为nil
,即使它们在条件语句中也是如此。
此代码:
unless resource.nil?
resource = resource.becomes(Accounts::Admin)
end
由于ruby中的另一个规则导致局部变量优先于方法而导致问题。因此,当您说resource = resource
时,您实际上正在调用方法resource
并将其值保存到局部变量resource
,然后将该方法用相同的名称覆盖。
最终你得到了错误:
未定义的方法`成为&#39;为零:NilClass
因为在编译时,正在创建局部变量resource
,使方法蒙上阴影。然后,在运行时,正在执行条件,因为resource
尚未nil
。但是在您创建局部变量的行中,它会立即进入范围,使resource
= nil
并导致错误。
错误可以在这个通用示例中重现:
def blah
"foo"
end
unless blah.nil?
blah = blah.size
end
puts blah
它的修复方法是指定方法本身:
def blah
"foo"
end
def blah= value
#do nothing
end
unless blah.nil?
self.blah = blah.size
end
puts blah
话虽如此,我不确定设计是否实际实现resource=()
。如果它没有,那么你最好的解决方案是你已经提出的 - 使用局部变量:
unless resource.nil?
res = resource.becomes(Accounts::Admin)
end
puts res
在做了一些研究之后,我发现ruby中的局部变量是根据文件中的位置从上到下和从左到右定义的,而不是它们在程序流中的位置。例如:
if x="foo"
puts x
end
#=> "foo"
puts y if y="foo"
#NameError: undefined variable or method 'y'
这是红宝石规范according to matz的一部分。
答案 1 :(得分:0)
在IRb中试试这个,应该没问题:
a = 'hello'
unless a.nil?
a = a.upcase
end
a
# => "HELLO"
第二个例子相当于第一个例子,=
右侧的表达式被分配给左边的var。
也许有些隐藏的字符或拼写错误?
你确定stacktrace指向那一行,你在文件的其他地方使用becomes
吗?
答案 2 :(得分:0)
如果使用ruby Ruby 2.3.0及更高版本,请使用安全导航操作符(&。)
resource = resource&.becomes(Accounts::Admin)