# StrongParams
[](https://github.com/Finbits/strong_params/actions?query=workflow%3ACI)
[](https://hex.pm/packages/strong_params)
[](https://hex.pm/packages/strong_params)
[](https://hex.pm/packages/strong_params)
[](https://codecov.io/gh/Finbits/strong_params)
Inspired by Ruby on Rails Strong Parameters. It filters request params keeping only explicitly enumerated parameters.
In addition, parameters can be marked as required and flow through a controller fallback flow to end up as a 400 Bad Request with no effort.
## Installation
Add `StrongParams` to your application
mix.exs
```elixir
def deps do
[
{:strong_params, "~> 0.2.2"}
]
end
```
Update deps
```sh
mix deps.get
```
## Usage
`StrongParams` uses macros to apply the parameters filter. You must `use` _StrongParams_
in each controller you want filter parameters. The better way is using _StrongParams_
in you Phoenix App entrypoint inside `controller/0` block (it must be add after
use `Phoenix.Controller`).
/lib/your_phoenix_app.ex
```elixir
defmodule YourPhoenixApp do
...
def controller do
quote do
use Phoenix.Controller, namespace: YourPhoenixApp
use StrongParams
...
end
end
end
```
Then you can use macro `filter_for/2` inside your controller to apply the filters
for each action.
```elixir
defmodule YourPhoenixApp.UserController do
use YourPhoenixApp, :controller
alias YourPhoenixApp.User
filter_for(:create, required: [:name, :email], permitted: [:nickname])
def create(conn, %{name: _, email: _} = params) do
user = %User{}
|> User.changeset(params)
|> Repo.insert()
render(conn, user: user)
end
end
```
In above example, once `filter_for/2` is defined for action `create` the second
argument received in action will be the filtered request parameters. The map `params`
has atomized keys, once the filter is defined as `atoms` (the lib don't create new atoms).
If some parameter enumerated as required is missing in received request the `Plug.Conn`
will be halted with status code `400` and a generic error message. If you add an
action fallback you can handle the filter error:
```elixir
defmodule YourPhoenixApp.UserController do
use YourPhoenixApp, :controller
action_fallback(YourPhoenixApp.Fallback)
filter_for(:create, required: [:name, :email], permitted: [:nickname])
...
end
defmodule YourPhoenixApp.Fallback do
alias StrongParams.Error
def call(conn, %Error{errors: errors}) do
send_resp(conn, 400, "Your custom msg #{inpect(errors)}")
end
end
```
You must call `filter_for/2` for each action you want to filter the params.
```elixir
filter_for(:create, required: [:name, :email], permitted: [:nickname])
filter_for(:update, permitted: [:name, :email, :nickname])
```
## Contributing
[Contributing Guide](CONTRIBUTING.md)
## License
[Apache License, Version 2.0](LICENSE) © [Finbits](https://github.com/Finbits)
