title: Shinydashboard error passing functions to variables
body: <p>I am planning to build a complex app and ideally I want to split parts into simplier parts in order to be easier for debugging and reading of my code. However, i get an error trying to implement that approach. Do I have to use <code>source()</code> function for this instead of passing by variables?
  Finally, what kind of approach do you recommend when trying to build a complex app?</p>
  <pre><code>library(shiny)
  library(shinydashboard)
  
  ui &lt;- dashboardPage(header = Header_app, sidebar = Sidebar_app, body = Body_app)
  
  Header_app &lt;- dashboardHeader(title = &quot;Hello&quot;)
  Sidebar_app &lt;- dashboardSidebar()
  Body_app &lt;- dashboardBody()
  
  server &lt;- function(input, output) {}
  
  shinyApp(ui, server)
  
  </code></pre>
  <p>The error i get is:</p>
  <p>Error in tagAssert(header, type = &quot;header&quot;, class = &quot;main-header&quot;) :
  object 'Header_app' not found</p>