[FIXED] Why does inserting a function inside a route differ from inserting the code inside the function in Flask?

Issue

I am trying to make a web app with a login system. I want to make it so that a user can't access certain pages unless they are logged in.

What I want is that when you click to go to another page while not logged in, you get redirected to the login page and on it you get a message flash.

This is what works:

@app.route("/home", methods=['GET', 'POST'])
def home():
    #some form
    if not current_user.is_authenticated:
        flash('You need to be logged in to access this page.', 'info')
        return redirect(url_for('login'))
    #rest of the code

But I would need to add all of this to other routes as well. So I created the function and added it to the routes instead:

@app.route("/home", methods=['GET', 'POST'])
def home():
    #some form
    require_login()
    #rest of the code

def require_login():
    if not current_user.is_authenticated:
        flash('You need to be logged in to access this page.', 'info')
        return redirect(url_for('login'))

But this does not work as I want it to. It instead redirects to the home page and then flashes the message. How do I fix this?

Solution

The problem is that the redirect(...) doesn't itself do the redirect. It returns a value to Flask telling flask that it needs to do the redirect.

In your first piece of code, you handle this correctly. You take the result of redirect(...) and return it to flask. In your second piece of code, you take the redirection returned by require_login and ignore it in home.

You might try something like:

value = require_login()
if value:
     return value

Answered By - Frank Yellin