editor of samples make table view item click disable

[charlescui]

I think this code occur error:eval script._UTF8String.to_s.
After click Run button in Editor view, nothing will eval.But return to root table view, every table item is diabled for click.

I changed editor.rb file's runScript function:

  define C::Void, :runScript, Cocoa::Object do |sender|
    # script = @editor_view._text._UTF8String.to_s    
    # str = eval(script._UTF8String.to_s)
    str = eval("1 + 1")
    alert = Cocoa::UIAlertView._alloc._initWithTitle "Hello",
      :message, (str || "I am MobiRuby"),
      :delegate, nil,
      :cancelButtonTitle, "I know!",
      :otherButtonTitles, _S("What's?"), nil
    alert._show
  end

If delete the code eval line, app run ok in ios simulator 6.1,else table view will disabled after Editor's Run button is clicked.