初始化并自动生成迁移

First add the package to your project. Flask-Migrate brings Alembic and a set of handy flask db commands. 📦

Create a Migrate object and bind it to your app and db. That single line activates the whole flask db command group.

Run flask db init once per project. It scaffolds a migrations folder that will hold every version script you generate.

The new folder holds an alembic.ini, an env.py, and an empty versions directory where future migration files will live.

flask db migrate compares your models to the live schema and writes a script describing exactly what changed.

Always pass a clear -m message. It labels the migration so your team can read the history like a changelog later.

Each migrate command drops a fresh file in versions, named with a random revision id plus your message slug.

Autogenerate only sees models that are actually imported when the command runs. Missing imports mean missing tables in the script.

Alembic diffs the model metadata against the database. It catches new tables, added columns, and many changed constraints automatically.

Key point: migrate only writes the script. Your database is still untouched until you actually apply it in the next lesson.

Treat migration files as code and commit them to git. Teammates replay the exact same changes from your version history.

You wired up Migrate, ran flask db init, and autogenerated a script with flask db migrate ready to apply. 🎉