redirect while passing arguments

Question

In flask, I can do this:

render_template("foo.html", messages={'main':'hello'}) 

And if foo.html contains {{ messages['main'] }}, the page will show hello. But what if there's a route that leads to foo:

@app.route("/foo") def do_foo():     # do some logic here     return render_template("foo.html") 

In this case, the only way to get to foo.html, if I want that logic to happen anyway, is through a redirect:

@app.route("/baz") def do_baz():     if some_condition:         return render_template("baz.html")     else:         return redirect("/foo", messages={"main":"Condition failed on page baz"})          # above produces TypeError: redirect() got an unexpected keyword argument 'messages' 

So, how can I get that messages variable to be passed to the foo route, so that I don't have to just rewrite the same logic code that that route computes before loading it up?

Answer 1

You could pass the messages as explicit URL parameter (appropriately encoded), or store the messages into session (cookie) variable before redirecting and then get the variable before rendering the template. For example:

from flask import session, url_for  def do_baz():     messages = json.dumps({"main":"Condition failed on page baz"})     session['messages'] = messages     return redirect(url_for('.do_foo', messages=messages))  @app.route('/foo') def do_foo():     messages = request.args['messages']  # counterpart for url_for()     messages = session['messages']       # counterpart for session     return render_template("foo.html", messages=json.loads(messages)) 

(encoding the session variable might not be necessary, flask may be handling it for you, but can't recall the details)

Or you could probably just use Flask Message Flashing if you just need to show simple messages.

Answer 2

I found that none of the answers here applied to my specific use case, so I thought I would share my solution.

I was looking to redirect an unauthentciated user to public version of an app page with any possible URL params. Example:

/app/4903294/my-great-car?email=coolguy%40gmail.com to

/public/4903294/my-great-car?email=coolguy%40gmail.com

Here's the solution that worked for me.

return redirect(url_for('app.vehicle', vid=vid, year_make_model=year_make_model, **request.args)) 

Hope this helps someone!