This module defines the behaviour for custom validators.

Validators can be defined inline in which case this behaviour need not be used, but if you want to define reusable validators which you can reference in your schema, you should implement this behaviour, and then import the application in your schema so that they are made available by the module name.

Example

app.schema.exs:

[ mappings: [
  "foo.bar": [
    datatype: :integer,
    default: 1,
    validators: [MyApp.RangeValidator: 1..2, MyApp.PositiveIntegerValidator]
  ]
]]

app.conf:

foo.bar = 3

In the example above, foo.bar will be first parsed and mapped as the integer value 3, and then validated by calling MyApp.RangeValidator.validate(3, [1..2]) where the second parameter is an optional list of extra arguments used by the validator. The second validator will then be called like MyApp.PositiveIntegerValidator.validate(3, []).

Validators must return :ok if validation passed, {:warn, message} if validation passed but a warning should be printed to stdout (for instance if you set a value to a valid but extreme value), or {:error, message} if validation failed.