How to display an error message upon invalid login and route back to username and password screen in ruby sinatra

Question

What I want to do is to be able to put an error message of my choosing if username/password combo is wrong I can just make another view but want to be able to just go back to login screen instead if having to go to a invalid login view I know there has to be something simple I can add on next line after :login but when i put "This is a sample error message" or something like that it just will display it and not bring me back to login screen.

post '/login' do
    authenticate
    if @auth == 1
        erb :main
    else 
        erb :login
    end
end

Answer 1

Well I figured out my issue Im not redirecting anymore i added a parameter to my code

Post '/login' do authenticate if @auth == 1 erb :main else erb:login,:locals => {:message => "Failed"} end end and

get '/login' do erb :login ,:locals => {:message => "!!Type in your username and password!!"}

and in my view file

<form action="/login" method="POST">
<input class="login" type="text" name="username" value="Username"><br>
<input class="login" type="password" name="password" value="Password"><br>
<input class="submit" type="submit" value="Submit...If you dare">
<form action="/login" method="POST">
<%=message%>

</form>