firemodel

Type-safe, cross-platform models for Firestore.

Google's Firestore offering is a fantastic way to add "real time" to your product in mere minutes. For simple products, what they provide out of the box makes a lot of sense. You get dynamic, reflection-based API wrappers that fit in with your existing code.

This approach breaks down, however, as you start to build against a complex or quickly changing data model, or when multiple developers need to interact with the same schema across multiple codebases.

Firemodel generates consistent models for all of your codebase automatically. Based on a single source of truth, your schema, firemodel generates idiomatic models for your firestore documents. These models are designed to work nicely with the standard Firestore SDKs and its 7 native types.

Firemodel currently supports iOS (Swift+Pring), TypeScript and Go.

Quick Start

Install firemodel with go get:

go get github.com/visor-tax/firemodel/firemodel

Now that you have the tool, you're ready to define a schema!

Note: this guide assumes you are already set up with Firestore in your project.

1. Define a Schema

Define a schema for all of the document types you work with.

schema.firemodel:

// An Aircraft is a machine that flies.
model Aircraft {
  // The airplane's official registration.
  string tailnumber;
  // The plane's current altitude.
  integer altitude;
  // The airplane's current autopilot setting.
  AutoPilotMode ap;
  // The state of the door on the left.
  Door left_door;
  // The state of the door on the right.
  Door right_door;
}

enum AutoPilotMode {
  manual,
  heading,
  alt,
  full_auto,
}

// Door is compound state.
// (Saved as an embedded object/map/dict in firestore.)
struct Door {
  bool is_closed;
  bool is_armed;
  bool is_secured;
}

The Schema is a platform independent way to describe the data you want to store in Firestore.

You can define as many models and enums as you'd like. See the example for a complete description of the type system.

2. Generate models

Open up a terminal, and generate your models:

firemodel compile \
    --schema='*.firemodel' \
    --go_out=./gen/go \
    --ts_out=./.gen/ts \
    --ios_out=./.gen/ios

This generated some Swift, some typescript and some go code. You'll find it in .gen directory, as requested. You can now incorporate these generated files into your project.

Note: It is possible to split up your schema into multiple files. The --schema flag is parsed using filepath.Glob. You can specify --schema multiple times. The order of schemas or cross-file references does not matter; all schema files are parsed in a single namespace.

This is the standard firemodel workflow. Whenever you need to update your data model, you'll update the schema and regenerate the models.

3. Use the models

The models are designed to be idiomatic for their target languages and the official Firestone SDKs.

In go, firemodel provides you with a tagged struct.

In iOS, firemodel provides a Pring Object subclass.

In typescript, firemodel provides interfaces and helpers classes.

It is trivial to extend firemodel with custom language providers. See the Modeler interface for more details.

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Schema Language & Type System

With Firemodel, you use a language loosely inspired by proto3 to define your data model.

In firemodel, whitespace is generally ignored, and semi-colons are required.

A model has fields, and each field has a type:

There's no type for nil, because it's silly to have a field that is always nil. Surprisingly, firestore represents nil as a type; that's not faithfully represented in firemodel.

The primitive types in firemodel match firestore's built-in types exactly:

Firemodel Type	Firestore Type
string	String
integer	Number
double	Double
timestamp	Timestamp
bytes	Bytes
reference	Reference
geopoint	GeoPoint
array	Array
map	Map

You can also define Enums:

enum TodoState {
  todo,
  done,
}

These enum values can be used as a field type:

model Todo {
  TodoState status;
}

Enums are not real. They end up as strings in firestore.

You can also make a struct type and embed it:

struct Amount {
  integer units;
  string currency;
}

model Product {
  Amount price;
}

Structs are not real. They end up getting stored as a Map in firestore.

collection provides a nested collection. Collections are somewhat real; they are not actually fields, but, rather, they provide access to the first-class feature in firestore.

Generics

Firemodel supports generics for map, array and reference.

Generic types can be firemodel primitives or user-defined types:

model Child {}

enum Emotion { HAPPY, SAD, }

model Thing {
  array<string> primitive_array;
  array<Child> model_array;
  array<Emotion> enum_array;
}

Generic generic types are supported:

model Thing {
  array<reference<T>>
}

Options

You can specify schema and model options via the following syntax:

option foo.bar = "baz";

model MyModel {
    option lang.key = "value";
}

Options are used to provide hints to the modelers.

Here are the currently supported options:

Option Name	Description	Example
firestore.model_name	Documents's collection name, sans path.	option firestore.path = "users";
firestore.path	Document's typical location in firestore, specified as a template with variables surrounded with curly braces.	option firestore.path = "users/{user_id}";
firestore.autotimestamp	Automatically add createdAt and updatedAt fields.	option firestore.autotimestamp = true;
ts.namespace	The TypeScript namespace for generated interfaces.	option ts.namespace = "SomeApp";
go.package	The name of the go package for generated code.	option go.package = "myapp";