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PORuby on Rails : NoMethodError
 

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  1. PORuby on Rails : NoMethodError
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    <p>I am a beginner in ROR .I faced a problem that when I test code on one book. I follow it stage by stage, but the error show up...</p> <p>NoMethodError in CaculatorController#calculate</p> <pre><code>undefined method `[]=' for nil:NilClass </code></pre> <p>Rails.root: /home/toth4321/calculator</p> <pre><code>app/controllers/caculator_controller.rb:4:in `set_charset' </code></pre> <p><strong>Controller</strong></p> <pre><code>class CaculatorController &lt; ApplicationController before_filter:set_charset def set_charset @headers['Content-Type'] = 'text/html; charset=GB2312' end def calculate if request.post? arg1 = convert_float(:arg1) arg2 = convert_float(:arg2) op = convert_operator(:operator) @result = op.call(arg1, arg2) end end private def convert_float(name) Float (params[name]) end def convert_operator(name) case params[name] when "+" then proc {|a,b| a+b} when "-" then proc {|a,b| a-b} when "*" then proc {|a,b| a*b} when "/" then proc {|a,b| a/b} end end end </code></pre> <p><strong>Views</strong></p> <pre><code>&lt;html&gt; &lt;head&gt; &lt;title&gt;簡單的網頁計算器&lt;/title&gt; &lt;/head&gt; &lt;body&gt; &lt;%= form_tag(:action =&gt; :calculate) %&gt; &lt;%= text_field_tag(:arg1, @params[:arg1], :size =&gt;3) %&gt; &lt;%= select_tag(:operator, options_for_select(%w{+ - * /})), @params[:operator])) %&gt; &lt;%= text_field_tag(:arg2, @params[:arg2], :size =&gt;3) %&gt; &lt;%= submit_tag（"送出"）　％&gt; &lt;% end_form_tag %&gt; &lt;b&gt;&lt;%= @result %&gt;&lt;/b&gt; &lt;/body&gt; &lt;/html&gt; </code></pre> <p>can somebody help me? Thanks a lot!</p>
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    1. USJui Cheng Lai
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