[Rails] How can I access the value of params[:tags] in my validate function?

[softwareengineer 99]

I would like to have tags mandatory in my app.
  
  The following keeps giving me error that params is nill.
  
   def validate()
    if (@params[:tags])
        errors.add(@params[:tags], ":tags must be entered ")
     end
   end
  
  Why cannot I access params in my model class?
  The field for tags is called "tags" 
  
  How else can I add an error using errors.add?
  
  I finally got to use flash[:notice] in my controller but I'm sure there is a better way to do this.
  
  Many thanks to the member of this great list for their assistance.
  
  Frank
  
		
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