Slate: An appointment booking app from every side

Slate is a sample app with a server behind it, for any business that sells time with a person: a salon, a tutor, a personal trainer, a consultancy, a clinic. Clients book an appointment and see only the times that are free. Providers run their day and connect their own calendars. The owner reads the numbers, keeps the catalogue and sets the rules every booking obeys. The app and the server are one Maven project, written in Java on both sides.

This chapter is the user’s guide: what each kind of user sees and can do. Slate: Building on the sample is the other half. It explains how the project is built and what to change to make it yours.

One app serves everyone. The server gives every account a set of roles, and the app offers a mode for each role the account holds. Someone who holds more than one switches between them from the menu.

Start the server on the development profile, which creates a demo salon and its accounts and simulates cards and the Google and Microsoft calendars:

Then run the app in the simulator:

Every demo account has the password slate-demo:

The demo is a salon. The same server can run as a tutoring business, a personal trainer, a consultancy or a clinic: the words change (a stylist and a chair become a tutor and a room), and every rule and screen stays the same.

Cards are simulated: 4242 4242 4242 4242 is accepted and 4000 0000 0000 0002 is declined. No money moves.

The client’s home leads with the next appointment and lists what can be booked, each service with its length and price.

Booking starts from a service. Pills at the top choose the location and the provider, or anyone who offers it, and a strip of days chooses when. The screen shows only the starts that are free. A start appears only when every rule agrees:

When a day has nothing, the screen says why — fully booked, not working that day, or too soon to book — and offers the waiting list. The week view shows the next seven days at once, for a client who cares about the time more than the day.

With Check my calendar on, the app reads the phone’s own calendars and marks any start that clashes with something already there. Only busy times are read, on the phone. Nothing about the client’s calendar is sent anywhere.

Choosing a start holds it for a few minutes, with a countdown, so nobody else can take it while the client decides. The confirm screen shows the price, the deposit if the business takes one, the card it comes from, and the terms: until when cancelling is free and what a no-show costs. A note answers the service’s question, if it has one ("Anything the stylist should know?"). Going back lets the time go.

Once it’s confirmed, the appointment can go into the phone’s calendar with a reminder an hour ahead. The event belongs to the app. When the appointment moves, the event moves with it, and when it’s cancelled, from any device, the event is deleted.

Upcoming bookings are listed in My appointments, a day at a time, and past ones below them. An appointment’s screen shows when, where, who with and what was paid. It says exactly what cancelling costs right now: free until a stated time, or the deposit kept once that time has passed. It can open the appointment as an .ics file for any calendar the app can’t write to.

Moving an appointment opens the same time picker with the same service and provider. The old time is kept until the new one is confirmed, so a move never loses the booking.

When a day is full, Tell me if a time frees up asks which part of the day suits and joins the list for that week. When a matching appointment is cancelled, the first person waiting gets a push notification. The time isn’t held, so the first person to book it gets it.

The provider’s home is their time: the day, the week or an agenda of what’s booked. One timeline merges their working hours, every appointment, their time off and every block that a connected calendar says is busy. When a client books or cancels, the timeline updates at once.

An appointment opens to the client’s name, note, and payment. Once it has started, the provider marks it done or missed. Before that, they can cancel it, which refunds the client in full and tells them at once.

Working hours sets the week: which days and from when to when. Saving replaces the whole week at once, so a half-edited week is never bookable. Time off blocks anything from an hour to a holiday. Appointments already booked inside it aren’t moved; the provider sees them and decides.

A provider’s other commitments keep clients away once their calendars are connected:

The dashboard covers the last few weeks: appointments booked and done, no-shows, cancellations, money taken and how full the providers' hours were. It also charts bookings by day and lists the most booked services and the busiest providers.

The Day board puts every provider’s day side by side, one column each. It’s wide enough on a tablet or a desktop to see who is free at a glance, and scrolls sideways on a phone.

Services, providers, locations, and rooms and equipment each have a list and an editor. A service has its length, price, buffers before and after, how many clients it takes at once, how many providers it needs, the kind of room it needs and its deposit. A provider has their title, a daily limit and a break after a long stretch. Nothing is deleted, only switched off, so past appointments keep the names they were booked under.

The rules decide which starts are offered:

Rules interact. A small step, a minimum gap and tight packing together offer far fewer starts than any one of them suggests. Preview tomorrow runs the edited rules against tomorrow’s real schedule without saving anything. It shows every provider’s starts, with the reason for each one that’s refused.

The server can host the app itself, so the whole business can be tried in a browser:

Then open http://localhost:8080/. A browser offers less than a phone: it can’t read the phone’s calendars or add events to them.