Ruby on rails RubyonRails：Rails3.0.10中没有方法错误

上面是宝石清单

我正在维护一个基本todo，它将在每个任务中定义子任务，但是命令

task=todo.tasks.new

不会导致方法错误

abstract (1.0.0)
actionmailer (3.2.2, 3.0.10, 3.0.5, 3.0.3, 2.3.5, 2.1.0)
actionpack (3.2.2, 3.0.10, 3.0.5, 3.0.3, 3.0.0.beta3, 2.3.5, 2.1.0)
activemodel (3.2.2, 3.0.10, 3.0.5, 3.0.3, 3.0.0.beta3)
activerecord (3.0.10)
activeresource (3.2.2, 3.0.10, 3.0.5, 3.0.3, 2.3.5, 2.1.0)
activesupport (3.2.2, 3.0.10, 3.0.5, 3.0.3, 3.0.0.beta3, 2.3.5, 2.1.0)
arel (3.0.2, 2.0.10, 2.0.6)
bcrypt-ruby (3.0.1, 2.1.2)
bson (1.1.5)
bson_ext (1.1.5)
builder (3.0.0, 2.1.2)
bundle (0.0.1)
bundler (1.1.3, 1.1.1, 1.1.0)
cancan (1.6.7, 1.4.1)
coffee-rails (3.2.2)
coffee-script (2.2.0)
coffee-script-source (1.3.1, 1.2.0)
devise (2.0.4, 1.5.3, 1.1.5)
erubis (2.7.0, 2.6.6)
execjs (1.3.0)
hike (1.2.1)
i18n (0.6.0, 0.5.0, 0.3.7)
journey (1.0.3)
jquery-rails (2.0.2, 2.0.1)
jquery_datepicker (0.3.4)
json (1.6.6, 1.6.5)
libv8 (3.3.10.4 x86-linux)
mail (2.4.4, 2.2.19, 2.2.12, 2.2.7)
memcache-client (1.8.5)
mime-types (1.18, 1.17.2, 1.16)
mongo (1.1.5)
mongoid (2.0.0.beta.20)
multi_json (1.2.0)
mysql2 (0.3.11)
nifty-generators (0.4.2)
orm_adapter (0.0.7)
polyglot (0.3.3, 0.3.1)
rack (1.4.1, 1.2.5, 1.2.1, 1.1.3, 1.0.1)
rack-cache (1.2)
rack-mount (0.6.14, 0.6.13)
rack-ssl (1.3.2)
rack-test (0.6.1, 0.5.7, 0.5.6)
rails (3.0.10)
railties (3.2.2, 3.0.10, 3.0.5, 3.0.3)
rake (0.9.2.2, 0.8.7)
rdoc (3.12)
rolify (3.1.0)
sass (3.1.15)
sass-rails (3.2.5)
sprockets (2.1.2)
sqlite3 (1.3.5)
therubyracer (0.9.10)
thor (0.14.6)
tilt (1.3.3)
treetop (1.4.10, 1.4.9)
tzinfo (0.3.33, 0.3.32, 0.3.23)
uglifier (1.2.4)
warden (1.1.1, 1.0.3)
will_paginate (3.0.3, 3.0.pre2)

amrit@PC148881：~/mytodos$rails控制台
加载开发环境（Rails 3.0.10）
1.9.2-p290:001>todo=todo.first
NoMethodError：当你没有预料到的时候，你有一个nil对象！
您可能期望数组的一个实例。
首先计算nil时出错
来自（irb）：1
from/home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/railties-3.0.10/lib/rails/commands/console.rb:44:in'start'
from/home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/railties-3.0.10/lib/rails/commands/console.rb:8:in'start'
from/home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/railties-3.0.10/lib/rails/commands.rb:23:in`'
来自脚本/rails:6:in'require'
来自脚本/rails:6:in`'
1.9.2-p290:002>todo=todo.first
=> # 
1.9.2-p290:003>任务=Todo.tasks.new
NoMethodError：未定义的方法“tasks”#
from/home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/activerecord-3.0.10/lib/active\u record/base.rb:1014:in'method\u missing'
来自（irb）：3
from/home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/railties-3.0.10/lib/rails/commands/console.rb:44:in'start'
from/home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/railties-3.0.10/lib/rails/commands/console.rb:8:in'start'
from/home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/railties-3.0.10/lib/rails/commands.rb:23:in`'
来自脚本/rails:6:in'require'
来自脚本/rails:6:in`'
1.9.2-p290:004>^C
1.9.2-p290:004>t=Task.new
=> # 
1.9.2-p290:005>t.description=“会议”
=>“会议”
1.9.2-p290:006>t.save
=>正确
1.9.2-p290:007>任务=Todo.tasks.new
NoMethodError：未定义的方法“tasks”#
from/home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/activerecord-3.0.10/lib/active\u record/base.rb:1014:in'method\u missing'
来自（irb）：7
from/home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/railties-3.0.10/lib/rails/commands/console.rb:44:in'start'
from/home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/railties-3.0.10/lib/rails/commands/console.rb:8:in'start'
from/home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/railties-3.0.10/lib/rails/commands.rb:23:in`'
来自脚本/rails:6:in'require'
来自脚本/rails:6:in`'
1.9.2-p290:008>

您可能无意中对类而不是实例调用了

任务。请尝试以下方法：

amrit@PC148881:~/mytodos$ rails console
Loading development environment (Rails 3.0.10)
1.9.2-p290 :001 > todo=todo.first
NoMethodError: You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.first
    from (irb):1
    from /home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/railties-3.0.10/lib/rails/commands/console.rb:44:in `start'
    from /home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/railties-3.0.10/lib/rails/commands/console.rb:8:in `start'
    from /home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/railties-3.0.10/lib/rails/commands.rb:23:in `<top (required)>'
    from script/rails:6:in `require'
    from script/rails:6:in `<main>'
1.9.2-p290 :002 > todo=Todo.first
 => #<Todo id: 1, name: "Office", description: "work to be completed at office", created_at: "2012-04-17 08:53:35", updated_at: "2012-04-17 08:53:35"> 
1.9.2-p290 :003 > task=Todo.tasks.new
NoMethodError: undefined method `tasks' for #<Class:0xae32588>
    from /home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/activerecord-3.0.10/lib/active_record/base.rb:1014:in `method_missing'
    from (irb):3
    from /home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/railties-3.0.10/lib/rails/commands/console.rb:44:in `start'
    from /home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/railties-3.0.10/lib/rails/commands/console.rb:8:in `start'
    from /home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/railties-3.0.10/lib/rails/commands.rb:23:in `<top (required)>'
    from script/rails:6:in `require'
    from script/rails:6:in `<main>'
1.9.2-p290 :004 > ^C
1.9.2-p290 :004 > t=Task.new
 => #<Task id: nil, description: nil, due_date: nil, due_time: nil, completed: nil, todo_id: nil, created_at: nil, updated_at: nil> 
1.9.2-p290 :005 > t.description="meeting"
 => "meeting" 
1.9.2-p290 :006 > t.save
 => true 
1.9.2-p290 :007 > task=Todo.tasks.new
NoMethodError: undefined method `tasks' for #<Class:0xae32588>
    from /home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/activerecord-3.0.10/lib/active_record/base.rb:1014:in `method_missing'
    from (irb):7
    from /home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/railties-3.0.10/lib/rails/commands/console.rb:44:in `start'
    from /home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/railties-3.0.10/lib/rails/commands/console.rb:8:in `start'
    from /home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/railties-3.0.10/lib/rails/commands.rb:23:in `<top (required)>'
    from script/rails:6:in `require'
    from script/rails:6:in `<main>'
1.9.2-p290 :008 > 

您可能无意中对类而不是实例调用了
任务。请尝试以下方法：

amrit@PC148881:~/mytodos$ rails console
Loading development environment (Rails 3.0.10)
1.9.2-p290 :001 > todo=todo.first
NoMethodError: You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.first
    from (irb):1
    from /home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/railties-3.0.10/lib/rails/commands/console.rb:44:in `start'
    from /home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/railties-3.0.10/lib/rails/commands/console.rb:8:in `start'
    from /home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/railties-3.0.10/lib/rails/commands.rb:23:in `<top (required)>'
    from script/rails:6:in `require'
    from script/rails:6:in `<main>'
1.9.2-p290 :002 > todo=Todo.first
 => #<Todo id: 1, name: "Office", description: "work to be completed at office", created_at: "2012-04-17 08:53:35", updated_at: "2012-04-17 08:53:35"> 
1.9.2-p290 :003 > task=Todo.tasks.new
NoMethodError: undefined method `tasks' for #<Class:0xae32588>
    from /home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/activerecord-3.0.10/lib/active_record/base.rb:1014:in `method_missing'
    from (irb):3
    from /home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/railties-3.0.10/lib/rails/commands/console.rb:44:in `start'
    from /home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/railties-3.0.10/lib/rails/commands/console.rb:8:in `start'
    from /home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/railties-3.0.10/lib/rails/commands.rb:23:in `<top (required)>'
    from script/rails:6:in `require'
    from script/rails:6:in `<main>'
1.9.2-p290 :004 > ^C
1.9.2-p290 :004 > t=Task.new
 => #<Task id: nil, description: nil, due_date: nil, due_time: nil, completed: nil, todo_id: nil, created_at: nil, updated_at: nil> 
1.9.2-p290 :005 > t.description="meeting"
 => "meeting" 
1.9.2-p290 :006 > t.save
 => true 
1.9.2-p290 :007 > task=Todo.tasks.new
NoMethodError: undefined method `tasks' for #<Class:0xae32588>
    from /home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/activerecord-3.0.10/lib/active_record/base.rb:1014:in `method_missing'
    from (irb):7
    from /home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/railties-3.0.10/lib/rails/commands/console.rb:44:in `start'
    from /home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/railties-3.0.10/lib/rails/commands/console.rb:8:in `start'
    from /home/amrit/.rvm/gems/ruby-1.9.2-p290@1.9.2/gems/railties-3.0.10/lib/rails/commands.rb:23:in `<top (required)>'
    from script/rails:6:in `require'
    from script/rails:6:in `<main>'
1.9.2-p290 :008 > 

这似乎是你正在做的一个简单的打字错误

todo=todo.first
，但是第二个
todo
是什么？因为你似乎还没有定义它；在您的第二个示例中，确实如此

task=todo.tasks.new

检查你用大写字母“T”所做的第二个例子，尝试更正它，或者你可以尝试

todo=Todo.first

（假设您有一个名为Todo的AR模型）
这似乎是您正在做的一个简单的打字错误

todo=todo.first
，但是第二个
todo
是什么？因为你似乎还没有定义它；在您的第二个示例中，确实如此

task=todo.tasks.new

检查你用大写字母“T”所做的第二个例子，尝试更正它，或者你可以尝试

todo=Todo.first

（假设您有一个名为Todo的AR模型）
谢谢！！我得到的答案是，我在创建实例时犯了一个错误。我正在尝试：t=Todo.new t=Todo.tasks.new而不是：t=Todo.new x=t.tasks。
谢谢！！我得到的答案是，我在创建实例时犯了一个错误。我尝试了以下操作：t=Todo.new t=Todo.tasks.new而不是：t=Todo.new x=t.tasks。
尝试只输入错误消息。。。。使其易读：请输入错误消息。。。。让它更具可读性：谢谢你！！我得到的答案是，我在创建实例时犯了一个错误，我尝试了以下操作：t=Todo.new t=Todo.tasks.new而不是：t=Todo.new x=t.tasks.new，因为我尝试在我的todoThanks中创建任务，这让您很高兴！！我得到的答案是，我在创建实例时犯了一个错误，我尝试了以下操作：t=Todo.new t=Todo.tasks.new而不是：t=Todo.new x=t.tasks.new，因为我尝试在我的Todo中创建任务