# A maintained fork of [Goal](https://github.com/martinthenth/goal) with extra functionality
[](https://github.com/mtanca/goal/actions/workflows/elixir.yml)
[](https://hex.pm/packages/m_goal)
[](https://hex.pm/packages/m_goal)
[](https://github.com/mtanca/m_goal/blob/main/LICENSE)
Goal is a parameter validation library based on [Ecto](https://github.com/elixir-ecto/ecto).
It can be used with JSON APIs, HTML controllers and LiveViews.
Goal builds a changeset from a validation schema and controller or LiveView parameters, and
returns the validated parameters or `Ecto.Changeset`, depending on the function you use.
If your frontend and backend use different parameter cases, you can recase parameter keys with
the `:recase_keys` option. `PascalCase`, `camelCase`, `kebab-case` and `snake_case` are
supported.
You can configure your own regexes for password, email, and URL format validations. This is
helpful in case of backward compatibility, where Goal's defaults might not match your production
system's behavior.
## Installation
Add `m_goal` to the list of dependencies in `mix.exs`:
```elixir
def deps do
[{:m_goal, "~> 1.2.3"}]
end
```
## Examples
Goal can be used with LiveViews and JSON and HTML controllers.
### Example with JSON and HTTP controllers
With JSON and HTML-based APIs, Goal takes the `params` from a controller action, validates those
against a validation schema using `validate/3`, and returns an atom-based map or an error
changeset.
```elixir
defmodule AppWeb.SomeController do
use AppWeb, :controller
use Goal
def create(conn, params) do
with {:ok, attrs} <- validate(:create, params)) do
...
else
{:error, changeset} -> {:error, changeset}
end
end
defparams :create do
required :uuid, :string, format: :uuid
required :name, :string, min: 3, max: 3
optional :age, :integer, min: 0, max: 120
optional :gender, :enum, values: ["female", "male", "non-binary"]
optional :hobbies, {:array, :string}, max: 3, rules: [trim: true, min: 1]
optional :data, :map do
required :color, :string
optional :money, :decimal
optional :height, :float
end
end
end
```
### Example with LiveViews
With LiveViews, Goal builds a changeset in `mount/3` that is assigned in the socket, and then it
takes the `params` from `handle_event/3`, validates those against a validation schema, and
returns an atom-based map or an error changeset.
```elixir
defmodule AppWeb.SomeLiveView do
use AppWeb, :live_view
use Goal
def mount(params, _session, socket) do
changeset = changeset(:new, %{})
socket = assign(socket, :changeset, changeset)
{:ok, socket}
end
def handle_event("validate", %{"some" => params}, socket) do
changeset = changeset(:new, params)
socket = assign(socket, :changeset, changeset)
{:noreply, socket}
end
def handle_event("save", %{"some" => params}, socket) do
with {:ok, attrs} <- validate(:new, params)) do
...
else
{:error, changeset} -> {:noreply, assign(socket, :changeset, changeset)}
end
end
defparams :new do
required :uuid, :string, format: :uuid
required :name, :string, min: 3, max: 3
optional :age, :integer, min: 0, max: 120
optional :gender, :enum, values: ["female", "male", "non-binary"]
optional :hobbies, {:array, :string}, max: 3, rules: [trim: true, min: 1]
optional :data, :map do
required :color, :string
optional :money, :decimal
optional :height, :float
end
end
end
```
### Example with GraphQL resolvers
With GraphQL, you may want to validate input fields without marking them as `non-null` to enhance
backward compatibility. You can use Goal inside GraphQL resolvers to validate the input fields:
```elixir
defmodule AppWeb.MyResolver do
use Goal
defparams(:create_user) do
required(:id, :uuid)
required(:input, :map) do
required(:first_name, :string)
required(:last_name, :string)
end
end
def create_user(args, info) do
with {:ok, attrs} <- validate(:create_user) do
...
end
end
end
```
### Example with isolated schemas
Validation schemas can be defined in a separate namespace, for example `AppWeb.MySchema`:
```elixir
defmodule AppWeb.MySchema do
use Goal
defparams :show do
required :id, :string, format: :uuid
optional :query, :string
end
end
defmodule AppWeb.SomeController do
use AppWeb, :controller
alias AppWeb.MySchema
def show(conn, params) do
with {:ok, attrs} <- MySchema.validate(:show, params) do
...
else
{:error, changeset} -> {:error, changeset}
end
end
end
```
## Features
### Presence checks
Sometimes all you need is to check if a parameter is present:
```elixir
use Goal
defparams :show do
required :id
optional :query
end
```
### Deeply nested maps
Goal efficiently builds error changesets for nested maps, and has support for lists of nested
maps. There is no limitation on depth.
```elixir
use Goal
defparams :show do
optional :nested_map, :map do
required :id, :integer
optional :inner_map, :map do
required :id, :integer
optional :map, :map do
required :id, :integer
optional :list, {:array, :integer}
end
end
end
end
iex(1)> validate(:show, params)
{:ok, %{nested_map: %{inner_map: %{map: %{id: 123, list: [1, 2, 3]}}}}}
```
### Powerful array validations
If you need expressive validations for arrays types, look no further!
Arrays can be made optional/required or the number of items can be set via `min`, `max` and `is`.
Additionally, `rules` allows specifying any validations that are available for the inner type.
Of course, both can be combined:
```elixir
use Goal
defparams do
required :my_list, {:array, :string}, max: 2, rules: [trim: true, min: 1]
end
iex(1)> Goal.validate_params(schema(), %{"my_list" => ["hello ", " world "]})
{:ok, %{my_list: ["hello", "world"]}}
```
### Readable error messages
Use `Goal.traverse_errors/2` to build readable errors. Phoenix by default uses
`Ecto.Changeset.traverse_errors/2`, which works for embedded Ecto schemas but not for the plain
nested maps used by Goal. Goal's `traverse_errors/2` is compatible with (embedded)
`Ecto.Schema`, so you don't have to make any changes to your existing logic.
```elixir
def translate_errors(changeset) do
Goal.traverse_errors(changeset, &translate_error/1)
end
```
### Recasing inbound keys
By default, Goal will look for the keys defined in `defparams`. But sometimes frontend applications
send parameters in a different format. For example, in `camelCase` but your backend uses
`snake_case`. For this scenario, Goal has the `:recase_keys` option:
```elixir
config :goal,
recase_keys: [from: :camel_case]
iex(1)> MySchema.validate(:show, %{"firstName" => "Jane"})
{:ok, %{first_name: "Jane"}}
```
### Recasing outbound keys
Use `recase_keys/2` to recase outbound keys. For example, in your views:
```elixir
config :goal,
recase_keys: [to: :camel_case]
defmodule AppWeb.UserJSON do
import Goal
def show(%{user: user}) do
recase_keys(%{data: %{first_name: user.first_name}})
end
def error(%{changeset: changeset}) do
recase_keys(%{errors: Goal.Changeset.traverse_errors(changeset, &translate_error/1)})
end
end
iex(1)> UserJSON.show(%{user: %{first_name: "Jane"}})
%{data: %{firstName: "Jane"}}
iex(2)> UserJSON.error(%Ecto.Changeset{errors: [first_name: {"can't be blank", [validation: :required]}]})
%{errors: %{firstName: ["can't be blank"]}}
```
### Bring your own regex
Goal has sensible defaults for string format validation. If you'd like to use your own regex,
e.g. for validating email addresses or passwords, then you can add your own regex in the
configuration:
```elixir
config :goal,
uuid_regex: ~r/^[[:alpha:]]+$/,
email_regex: ~r/^[[:alpha:]]+$/,
password_regex: ~r/^[[:alpha:]]+$/,
url_regex: ~r/^[[:alpha:]]+$/
```
### Flexible key aliases
Goal allows you to map the value of an aliased key within a payload to a given field:
```elixir
use Goal
defparams :message_confirmation_webhook do
required(:message_provider_id, :string, key_aliases: ["twilio_id", "podium_id", "sengrid_id"])
required(:delivered_at, :string, key_aliases: ["sent_at", "timestamp", "confirmed_at"])
end
iex(1)> MySchema.validate(:message_confirmation_webhook, %{"sengrid_id" => "1234", "timestamp" => "2024-11-01T14:00:00Z"})
{:ok, %{message_provider_id: "1234", delivered_at: "2024-11-01T14:00:00Z"}}
```
### Available options
The field types and available options are:
| Field type | Validations | Description |
| ---------------------- | --------------------------- | ---------------------------------------------------------------------------------------------------- |
| `:uuid` | `:equals` | string value |
| `:string` | `:equals` | string value |
| | `:is` | exact string length |
| | `:min` | minimum string length |
| | `:max` | maximum string length |
| | `:trim` | boolean to remove leading and trailing spaces |
| | `:squish` | boolean to trim and collapse spaces |
| | `:format` | `:uuid`, `:email`, `:password`, `:url` |
| | `:subset` | list of required strings |
| | `:included` | list of allowed strings |
| | `:excluded` | list of disallowed strings |
| `:integer` | `:equals` | integer value |
| | `:is` | integer value |
| | `:min` | minimum integer value |
| | `:max` | maximum integer value |
| | `:greater_than` | minimum integer value |
| | `:less_than` | maximum integer value |
| | `:greater_than_or_equal_to` | minimum integer value |
| | `:less_than_or_equal_to` | maximum integer value |
| | `:equal_to` | integer value |
| | `:not_equal_to` | integer value |
| | `:subset` | list of required integers |
| | `:included` | list of allowed integers |
| | `:excluded` | list of disallowed integers |
| `:float` | | all of the integer validations |
| `:decimal` | | all of the integer validations |
| `:boolean` | `:equals` | boolean value |
| `:date` | `:equals` | date value |
| `:time` | `:equals` | time value |
| `:enum` | `:values` | list of allowed values |
| `:map` | `:properties` | use `:properties` to define the fields |
| `{:array, :map}` | `:properties` | use `:properties` to define the fields |
| `{:array, inner_type}` | `:rules` | `inner_type` can be any basic type. `rules` supported all validations available for `inner_type` |
| | `:min` | minimum array length |
| | `:max` | maximum array length |
| | `:is` | exact array length |
| More basic types | | See [Ecto.Schema](https://hexdocs.pm/ecto/Ecto.Schema.html#module-primitive-types) for the full list |
| Custom validations | `:custom` | expects a function taking a field name, params map, and a changeset, returning a changeset |
| Key aliases | `:key_aliases` | maps the value of any aliased key in a payload to a given field. expects a list of aliases |
All field types, excluding `:map` and `{:array, :map}`, can use `:equals`, `:subset`,
`:included`, `:excluded` validations.
## Credits
This library is based on [Ecto](https://github.com/elixir-ecto/ecto) and I had to copy and adapt
`Ecto.Changeset.traverse_errors/2`. Thanks for making such an awesome library! 🙇
