054-flask/docs/wiki/Lecture-6-Decorators.md

Lecture 6: Decorators and the @ syntax

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What the lecture covers

A decorator adds behaviour to an existing function without editing it. The lecture first recaps first-class functions, nesting and returning functions, then introduces the @ syntax: writing @make_bold above a function is the same as say_hello = make_bold(say_hello). Flask uses the same idea for its routes: @app.route("/"). With functools.wraps the wrapped function keeps its name.

What we gained

• The @ syntax as shorthand for passing a function to a wrapper.
• Stacking decorators: the one nearest the function runs first, so @make_bold @make_emphasis @make_underlined gives <b><em><u>...</u></em></b>.
• An understanding of what @app.route("/") does in the next lectures.

In this repository

Code: src/flask_day_54/domain/decorators.py. Tests: tests/unit/test_decorators.py.