The Booking sample app demonstrates (browse the source):
-
Using an SQL (SQLite) database and configuring the Revel DB module.
-
Using the third party GORP ORM-ish library
-
Interceptors for checking that an user is logged in.
-
Using validation and displaying inline errors
booking/app/ models # Structs and validation. booking.go hotel.go user.go
controllers init.go # Register all of the interceptors. gorp.go # A plugin for setting up Gorp, creating tables, and managing transactions. app.go # "Login" and "Register new user" pages hotels.go # Hotel searching and booking views ...
The booking app uses go-sqlite3 database driver (which wraps the native C library).
- Install Homebrew if you don't already have it.
- Install pkg-config and sqlite3:
$ brew install pkgconfig sqlite3
$ sudo apt-get install sqlite3 libsqlite3-dev
Once you have SQLite installed, it will be possible to run the booking app:
$ revel run github.com/revel/samples/booking
app/controllers/gorp.go
defines GorpPlugin
, which is a plugin that does a couple things:
- OnAppStart: Uses the DB module to open a SQLite in-memory database, create the User, Booking, and Hotel tables, and insert some test records.
- BeforeRequest: Begins a transaction and stores the Transaction on the Controller
- AfterRequest: Commits the transaction. Panics if there was an error.
- OnException: Rolls back the transaction.
app/controllers/init.go
registers the interceptors that run before every action:
{% highlight go %} func init() { revel.OnAppStart(Init) revel.InterceptMethod((*GorpController).Begin, revel.BEFORE) revel.InterceptMethod(Application.AddUser, revel.BEFORE) revel.InterceptMethod(Hotels.checkUser, revel.BEFORE) revel.InterceptMethod((*GorpController).Commit, revel.AFTER) revel.InterceptMethod((*GorpController).Rollback, revel.FINALLY) } {% endhighlight %}
As an example, checkUser
looks up the username in the session and redirects
the user to log in if they are not already.
{% highlight go %} func (c Hotels) checkUser() revel.Result { if user := c.connected(); user == nil { c.Flash.Error("Please log in first") return c.Redirect(Application.Index) } return nil } {% endhighlight %}
Check out the user management code in app.go
The booking app does quite a bit of validation.
For example, here is the routine to validate a booking, from models/booking.go:
{% highlight go %} func (booking Booking) Validate(v *revel.Validation) { v.Required(booking.User) v.Required(booking.Hotel) v.Required(booking.CheckInDate) v.Required(booking.CheckOutDate)
v.Match(b.CardNumber, regexp.MustCompile(`\d{16}`)).
Message("Credit card number must be numeric and 16 digits")
v.Check(booking.NameOnCard,
revel.Required{},
revel.MinSize{3},
revel.MaxSize{70},
)
} {% endhighlight %}
Revel applies the validation and records errors using the name of the
validated variable (unless overridden). For example, booking.CheckInDate
is
required; if it evaluates to the zero date, Revel stores a ValidationError
in
the validation context under the key "booking.CheckInDate".
Subsequently, the
Hotels/Book.html
template can easily access them using the field
helper:
{% capture ex %}{% raw %} {{with $field := field "booking.CheckInDate" .}}
Check In Date: * {{$field.Error}} ss
{{end}} {% endraw %}{% endcapture %} {% highlight htmldjango %}{{ex}}{% endhighlight %}The field
template helper looks for errors in the validation context, using
the field name as the key.