In flask should I ever redirect to the same route?-CodePudding

In flask should I ever redirect to the same route? FWIW the code below is the register route. Also does flash messages work before redirects or render_template ?

Just to confirm, I think I can redirect to another route or render_template without causing any errors. Is this correct?

Here is an example where I think why redirects to the same routes will cause an error.

I am using wtf forms. In wtf forms I have a username email password confirmation_password for the register routes forms.

@userinfo.route("/register", methods = ['POST', 'GET'])
def register():
    form = RegistrationForm()
    # if the value other then None, iow's you have a username in the database
    # The try is used if the database table User is empty. 
    if form.validate_on_submit():
    
        try:   
            all_usernames = User.query.filter_by(username=form.username.data).all()
                flash ("The usesrname is already taken. Please select another username.")     
        except: 
            all_usernames = None        
                   
        finally:
            # do I want to redirect to register route?
            if all_usernames == forms_username:
                return redirect(url_for('userinfo.register')) 

    return render_template("register.html", title=register, form=form)

I can show the html but I don't think it is needed Thanks.

Summary of browser steps.

step 1) I call the register function

step 2) Its starts off as a GET request and runs render_template because it skips form.validate_on_submit(). The register.html then runs.

step 3) I fill the information in the forms which username etc.

step 4) The POST request starts. This causes form.validate_on_submit() to run and all the code in between to run. Then instead of render_template I should redirect to a route. When I redirect I should get a GET request.

CodePudding user response：

Redirecting to the same route should not cause any problems.

But you need to know when to redirect to the same route. Redirecting to the same route after a POST request removes any data from the previous request. For example: if a user submitted a form and you want to show him a validation error you will not be able to, in this case you need to use render_tempate() instead.

In you example you will use redirect() if the registration was successful and there is not validation error, otherwise use render_tempate()