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33 lines
1.4 KiB
33 lines
1.4 KiB
Step 4: Request Database Connections |
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Now we know how we can open database connections and use them for scripts, |
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but how can we elegantly do that for requests? We will need the database |
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connection in all our functions so it makes sense to initialize them |
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before each request and shut them down afterwards. |
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Flask allows us to do that with the :meth:`~flask.Flask.before_request` and |
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:meth:`~flask.Flask.after_request` decorators:: |
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@app.before_request |
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def before_request(): |
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g.db = connect_db() |
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@app.after_request |
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def after_request(response): |
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g.db.close() |
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return response |
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Functions marked with :meth:`~flask.Flask.before_request` are called before |
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a request and passed no arguments, functions marked with |
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:meth:`~flask.Flask.after_request` are called after a request and |
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passed the response that will be sent to the client. They have to return |
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that response object or a different one. In this case we just return it |
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unchanged. |
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We store our current database connection on the special :data:`~flask.g` |
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object that flask provides for us. This object stores information for one |
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request only and is available from within each function. Never store such |
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things on other objects because this would not work with threaded |
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environments. That special :data:`~flask.g` object does some magic behind |
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the scenes to ensure it does the right thing.
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