Pluggable Method Views broken by fix for #570

[ajford]

So I'm not sure if this is meant to happen, but when you attempt to use MethodViews as described in the docs http://flask.pocoo.org/docs/views/#method-views-for-apis, I get an Assertion Error generated by the app.add_url_rule added in 661ee54. This commit was created to fix #570.

The MethodView example in the docs calls for registering multiple routes to the same class, which causes an AssertionError to be raised.

Is there another way to create a method based set of views without causing this error to be raised? Would it be better to switch from an AssertionError to a Warning that could be ignored?

[rplopes]

Same problem here, as referenced in #796. Some code works for 0.9 and breaks in 0.10.

[untitaker]

I suppose a quick fix for this would be to call MethodView.as_view for each add_url_rule, since this will generate a separate function for each route.

Ignore me.

[untitaker]

Actually this has been fixed with 44e39ab

[ajford]

Ok, after digging around, I figured out the problem.

If you call MethodView.as_view for each add_url_rule, the unique views for each route cause the Assertion error to be raised.

If you call foo = MethodView.as_view() then use foo for each of the add_url_rule calls, it will not cause the Assertion error. See https://gist.github.com/ajford/6023148

If you run app.py and app2.py against flask 0.8, flask 0.10, you'll see that in flask 0.8, both files run, while in flask 0.10+, only app2.py works.

Not an obvious complication. One I glossed over each time I reviewed the code and the Docs concerning add_url_rule and the classed based views.

[mitsuhiko]

Working as intended. If you use class based views and you assign more than one rule to the same handler you need to actually use the same handler. eg: create the view function once, bind it to a local variable and then assign it multiple times. The old behavior of silently ignoring it was dangerous as it did not inform you that you created and destroyed your handler multiple times and only the last one won.

[michaelbukachi]

Hello, I seem to be getting this error with the latest version of flask(0.11). I've tried ajford's solution but its still not working.

[davidism]

@michaelbukachi that solution (creating the view once and adding rules with it multiple times) is correct. If you have questions about your own code please ask on Stack Overflow with a Minimal, Complete, and Verifiable Example.

[michaelbukachi]

Sorry about that. Found the bug in my code. I feel so silly:)