# Parameter
<!-- MDOC !-->
`Parameter` is a library for dealing with complex datatypes by solving the following problems:
- Schema creation and validation
- Input data validation
- Deserialization
- Serialization
First step is to create a schema
```elixir
defmodule User do
use Parameter.Schema
alias Parameter.Validators
param do
field :first_name, :string, key: "firstName", required: true
field :last_name, :string, key: "lastName"
field :email, :string, validator: &Validators.email(&1)
has_one :address, Address do
field :city, :string, required: true
field :street, :string
field :number, :integer
end
end
end
```
Load (deserialize) the schema against external parameters:
```elixir
iex> params = %{
"firstName" => "John",
"lastName" => "Doe",
"email" => "john@email.com",
"address" => %{"city" => "New York", "street" => "York"}
}
...> Parameter.load(User, params)
{:ok, %{
first_name: "John",
last_name: "Doe",
email: "john@email.com",
main_address: %{city: "New York", street: "York"}
}}
```
or Dump (serialize) a populated schema to params:
```elixir
iex> schema = %{
first_name: "John",
last_name: "Doe",
email: "john@email.com",
main_address: %{city: "New York", street: "York"}
}
...> Parameter.dump(User, params)
{:ok,
%{
"firstName" => "John",
"lastName" => "Doe",
"email" => "john@email.com",
"address" => %{"city" => "New York", "street" => "York"}
}}
```
## Installation
Add `parameter` to your list of dependencies in `mix.exs`:
```elixir
def deps do
[
{:parameter, "~> 0.5"}
]
end
```
add `:parameter` on `.formatter.exs`:
```elixir
import_deps: [:ecto, :phoenix, ..., :parameter],
```
## Motivation
Offer a similar Schema model from [Ecto](https://github.com/elixir-ecto/ecto) library to deal with complex data schemas. The main use case is to parse response from external apis. `Parameter` provides a well structured schema model which tries it's best to parse the external data.
## Data Deserialization
This is a common requirement when receiving data from an external source that needs validation and deserialization of data to an Elixir definition. This can be achieved using `Parameter.load/2` or `Parameter.load/3` functions:
```elixir
iex> params = %{
"mainAddress" => %{"city" => "New York"},
"phones" => [%{"country" => "USA", "number" => "123456789"}],
"firstName" => "John",
"lastName" => "Doe"
}
...> Parameter.load(User, params)
{:ok,
%{
first_name: "John",
last_name: "Doe",
main_address: %{city: "New York"},
phones: [%{country: "USA", number: 123456789}]
}}
```
Return struct fields
```elixir
...> Parameter.load(User, params, struct: true)
{:ok,
%User{
first_name: "John",
last_name: "Doe",
main_address: %Address{city: "New York", number: nil, street: nil},
phones: [%Phone{country: "USA", number: 123456789}]
}}
```
Invalid data should return validation errors:
```elixir
iex> params = %{
"mainAddress" => %{"city" => "New York", "number" => "123AB"},
"phones" => [
%{
"country" => "USA",
"number" => "123AB"
},
%{
"country" => "Brazil",
"number" => "Not number"
}
],
"lastName" => "Doe"
}
...> Parameter.load(User, params)
{:error,
%{
first_name: "is required",
main_address: %{number: "invalid integer type"},
phones: [
"0": %{number: "invalid integer type"},
"1": %{number: "invalid integer type"}
]
}}
```
The options for `Parameter.load/3` are:
- `struct`: If `true` returns the response with elixir structs. `false` uses plain maps.
- `unknown`: Defines the behaviour when dealing with unknown fields on input data. The options are `:ignore` and `:error`
## Data Serialization
This is a common requirement when dealing with internal data that needs to be send to an external source. This can be achieved using `Parameter.dump/2` function:
```elixir
iex> loaded_params = %{
phones: [%{country: "USA", number: 123456789}],
first_name: "John",
last_name: "Doe",
main_address: %{city: "New York"}
}
...> Parameter.dump(User, loaded_params)
{:ok,
%{
"firstName" => "John",
"lastName" => "Doe",
"mainAddress" => %{"city" => "New York"},
"phones" => [%{"country" => "USA", "number" => 123456789}]
}}
```
## Unknown fields
Loading will ignore fields that does not have a matching key in the schema.
This behaviour can be changed with the following options:
- `:ignore` (default): ignore unknown fields
- `:error`: return an error with the unknown fields
Using the same user schema, adding unknow field option to error should return an error:
```elixir
iex> params = %{"user_token" => "3hgj81312312"}
...> Parameter.load(User, params, unknown: :error)
{:error, %{"user_token" => "unknown field"}}
```
## Validation
Parameter comes with a set of validators to validate the schema after loading. The implemented validators are described in the module `Parameter.Validators`.
```elixir
defmodule User do
use Parameter.Schema
alias Parameter.Validators
param do
field :email, :string, validator: &Validators.email/1
field :age, :integer, validator: {&Validators.length/2, min: 18, max: 72}
field :code, :string, validator: {&Validators.regex/2, regex: ~r/code/}
field :user_code, :string, validator: {&__MODULE__.is_equal/2, to: "0000"}
field :permission, :atom,
required: true,
validator: {&Validators.one_of/2, options: [:admin, :normal]}
end
# To add a custom validator create a function with arity 1 or 2.
# The first parameter is always the field value and the second (and optional)
# parameter is a `Keyword` list that will be used to pass values on the schema
# The function must always return `:ok` or `{:error, reason}`
def is_equal(value, to: to_value) do
if value == to_value do
:ok
else
{:error, "not equal"}
end
end
end
```
Sending wrong parameters:
```elixir
iex> params = %{
"email" => "not email",
"age" => "12",
"code" => "asdf",
"user_code" => "12345",
"permission" => "super_admin"
}
...> Parameter.load(User, params)
{:error,
%{
age: "is invalid",
code: "is invalid",
email: "is invalid",
permission: "is invalid",
user_code: "not equal"
}}
```
Correct input should result in the schema loaded correctly:
```elixir
iex> params = %{
"email" => "john@email.com",
"age" => "22",
"code" => "code:13234",
"permission" => "admin",
"user_code" => "0000"
}
...> Parameter.load(User, params)
{:ok,
%{
age: 22,
code: "code:13234",
email: "john@email.com",
permission: :admin,
user_code: "0000"
}}
```
## Excluding fields on serialization and deserialization
Pass the `exclude` key on the third argument of `Parameter.load/3` or `Parameter.dump/3` with a list of the fields to be excluded. Those fields won't be considered when serializing/deserializing the parameters.
```elixir
iex> params = %{
"firstName" => "John",
"lastName" => "Doe",
"email" => "john@email.com",
"address" => %{"city" => "New York", "street" => "York"}
}
...> Parameter.load(User, params, exclude: [:first_name])
{:ok, %{
last_name: "Doe",
email: "john@email.com",
address: %{city: "New York", street: "York"}
}}
...> Parameter.load(User, params, exclude: [:first_name, {:address, [:street]}])
{:ok, %{
last_name: "Doe",
email: "john@email.com",
address: %{city: "New York"}
}}
```
