NoMethodError（未定義的方法`提取'爲零：NilClass）

問題是通過Web套接字使用ActionCable廣播數據。該錯誤似乎表明它來自創建方法。NoMethodError（未定義的方法`提取'爲零：NilClass）

錯誤消息

Rendered weight/_weight.html.erb (1.1ms) 
[ActionCable] Broadcasting to weight: "<div class=\"row\">\n <div class=\"col-md-8 well\">\n <p>12.0 kg</p>\n <small>less than a minute</small>\n </div>\n</div>" 
Completed 500 Internal Server Error in 25ms (Views: 7.4ms | ActiveRecord: 10.6ms) 



NoMethodError (undefined method `fetch' for nil:NilClass): 

app/controllers/weight_controller.rb:7:in `create' 
Rendering /usr/local/rvm/gems/ruby-2.3.4/gems/actionpack-5.0.4/lib/action_dispatch/middleware/templates/rescues/diagnostics.text.erb 
Rendering /usr/local/rvm/gems/ruby-2.3.4/gems/actionpack-5.0.4/lib/action_dispatch/middleware/templates/rescues/_source.text.erb 
Rendered /usr/local/rvm/gems/ruby-2.3.4/gems/actionpack-5.0.4/lib/action_dispatch/middleware/templates/rescues/_source.text.erb (0.8ms) 
Rendering /usr/local/rvm/gems/ruby-2.3.4/gems/actionpack-5.0.4/lib/action_dispatch/middleware/templates/rescues/_trace.text.erb 
Rendered /usr/local/rvm/gems/ruby-2.3.4/gems/actionpack-5.0.4/lib/action_dispatch/middleware/templates/rescues/_trace.text.erb (0.9ms) 
Rendering /usr/local/rvm/gems/ruby-2.3.4/gems/actionpack-5.0.4/lib/action_dispatch/middleware/templates/rescues/_request_and_response.text.erb 
Rendered /usr/local/rvm/gems/ruby-2.3.4/gems/actionpack-5.0.4/lib/action_dispatch/middleware/templates/rescues/_request_and_response.text.erb (1.1ms) 
Rendered /usr/local/rvm/gems/ruby-2.3.4/gems/actionpack-5.0.4/lib/action_dispatch/middleware/templates/rescues/diagnostics.text.erb (25.0ms)

從controller.rb創建方法

def create 
    @weight = Weight.new(weight_params) 
    @weight.user_id = current_user.id 
    if @weight.save 
     ActionCable.server.broadcast "weight", render(partial: 'weight/weight', object: @weight) 

    else 
     flash[:danger] = "New Weight was not added!" 
     redirect_to current_user 
    end 
end 

private 

def weight_params 
    params.require(:weights).permit(:weight) 
end

我只是不能工作了什麼是返回零。信息在廣播重量方面正確的事實是正確的，這表明它已將其正確保存到數據庫中。想不到還有什麼執行'fetch'方法。

很確定網絡套接字設置正確。見下文。

配置/ application.rb中：

config.action_cable.mount_path = '/cable'

配置/ routes.rb中：

mount ActionCable.server => '/cable'

weight_channel.rb：

def subscribed 
    stream_from "weight" 
end

weight.coffee：

received: (data) -> 
    $("#messages").prepend(data)

來源

2017-09-24 will

線是'weight_controller.rb'文件的第7行？你在哪裏（如果）調用'fetch'？（在模型的視圖中？在由'save'調用的驗證中）？ – Myst

第7行是上述摘錄中的第5行。我沒有在任何地方使用抓取。 – will

爲了調試目的，考慮將'render'與'broadcast'分開，並將其放在兩條不同的行中。即：'tmp = render（partial：'weight/weight'，object：@weight）'new line'ActionCable.server.broadcast「weight」，tmp' ...讓我們知道哪一行（哪個方法調用）引發新錯誤。 – Myst

引發錯誤，原因是缺少config/cable.yml文件。

解決方案是使用config/cable.yml以及應用程序所需的設置。即：

# Action Cable uses Redis by default to administer connections, channels, and sending/receiving messages over the WebSocket. 
production: 
    adapter: redis 
    url: redis://localhost:6379/1 

development: 
    adapter: redis 
    url: redis://localhost:6379/1 

staging: 
    adapter: redis 
    url: redis://localhost:6379/1 

test: 
    adapter: async

該決議出現在問題的評論。

來源

2017-09-24 19:08:39 Myst

NoMethodError（未定義的方法`提取'爲零：NilClass）

回答

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