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Diffstat (limited to 'app/static/doc/flask-docs/_sources/patterns/urlprocessors.txt')
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diff --git a/app/static/doc/flask-docs/_sources/patterns/urlprocessors.txt b/app/static/doc/flask-docs/_sources/patterns/urlprocessors.txt deleted file mode 100644 index 778a5a6..0000000 --- a/app/static/doc/flask-docs/_sources/patterns/urlprocessors.txt +++ /dev/null @@ -1,126 +0,0 @@ -Using URL Processors -==================== - -.. versionadded:: 0.7 - -Flask 0.7 introduces the concept of URL processors. The idea is that you -might have a bunch of resources with common parts in the URL that you -don't always explicitly want to provide. For instance you might have a -bunch of URLs that have the language code in it but you don't want to have -to handle it in every single function yourself. - -URL processors are especially helpful when combined with blueprints. We -will handle both application specific URL processors here as well as -blueprint specifics. - -Internationalized Application URLs ----------------------------------- - -Consider an application like this:: - - from flask import Flask, g - - app = Flask(__name__) - - @app.route('/<lang_code>/') - def index(lang_code): - g.lang_code = lang_code - ... - - @app.route('/<lang_code>/about') - def about(lang_code): - g.lang_code = lang_code - ... - -This is an awful lot of repetition as you have to handle the language code -setting on the :data:`~flask.g` object yourself in every single function. -Sure, a decorator could be used to simplify this, but if you want to -generate URLs from one function to another you would have to still provide -the language code explicitly which can be annoying. - -For the latter, this is where :func:`~flask.Flask.url_defaults` functions -come in. They can automatically inject values into a call for -:func:`~flask.url_for` automatically. The code below checks if the -language code is not yet in the dictionary of URL values and if the -endpoint wants a value named ``'lang_code'``:: - - @app.url_defaults - def add_language_code(endpoint, values): - if 'lang_code' in values or not g.lang_code: - return - if app.url_map.is_endpoint_expecting(endpoint, 'lang_code'): - values['lang_code'] = g.lang_code - -The method :meth:`~werkzeug.routing.Map.is_endpoint_expecting` of the URL -map can be used to figure out if it would make sense to provide a language -code for the given endpoint. - -The reverse of that function are -:meth:`~flask.Flask.url_value_preprocessor`\s. They are executed right -after the request was matched and can execute code based on the URL -values. The idea is that they pull information out of the values -dictionary and put it somewhere else:: - - @app.url_value_preprocessor - def pull_lang_code(endpoint, values): - g.lang_code = values.pop('lang_code', None) - -That way you no longer have to do the `lang_code` assigment to -:data:`~flask.g` in every function. You can further improve that by -writing your own decorator that prefixes URLs with the language code, but -the more beautiful solution is using a blueprint. Once the -``'lang_code'`` is popped from the values dictionary and it will no longer -be forwarded to the view function reducing the code to this:: - - from flask import Flask, g - - app = Flask(__name__) - - @app.url_defaults - def add_language_code(endpoint, values): - if 'lang_code' in values or not g.lang_code: - return - if app.url_map.is_endpoint_expecting(endpoint, 'lang_code'): - values['lang_code'] = g.lang_code - - @app.url_value_preprocessor - def pull_lang_code(endpoint, values): - g.lang_code = values.pop('lang_code', None) - - @app.route('/<lang_code>/') - def index(): - ... - - @app.route('/<lang_code>/about') - def about(): - ... - -Internationalized Blueprint URLs --------------------------------- - -Because blueprints can automatically prefix all URLs with a common string -it's easy to automatically do that for every function. Furthermore -blueprints can have per-blueprint URL processors which removes a whole lot -of logic from the :meth:`~flask.Flask.url_defaults` function because it no -longer has to check if the URL is really interested in a ``'lang_code'`` -parameter:: - - from flask import Blueprint, g - - bp = Blueprint('frontend', __name__, url_prefix='/<lang_code>') - - @bp.url_defaults - def add_language_code(endpoint, values): - values.setdefault('lang_code', g.lang_code) - - @bp.url_value_preprocessor - def pull_lang_code(endpoint, values): - g.lang_code = values.pop('lang_code') - - @bp.route('/') - def index(): - ... - - @bp.route('/about') - def about(): - ... |