Ensure an attribute is set to a positive (or custom) value.

For use especially with "acceptance of terms" checkboxes in web applications.

Options

• :as: Optional. A custom value (eg, "yes"). By default any "truthy" value constitutes acceptance.
• :message: Optional. A custom error message. May be in EEx format and use the fields described in "Custom Error Messages," below.

Examples

iex> Vex.Validators.Acceptance.validate(1, true)
:ok
iex> Vex.Validators.Acceptance.validate(nil, true)
{:error, "must be accepted"}
iex> Vex.Validators.Acceptance.validate(nil, message: "must be accepted!")
{:error, "must be accepted!"}
iex> Vex.Validators.Acceptance.validate(1, [as: "yes"])
{:error, ~S(must be accepted with `"yes"`)}
iex> Vex.Validators.Acceptance.validate("verily", [as: "verily"])
:ok

Custom Error Messages

Custom error messages (in EEx format), provided as :message, can use the following values:

iex> Vex.Validators.Acceptance.__validator__(:message_fields)
[value: "The bad value"]

An example:

iex> Vex.Validators.Acceptance.validate(nil, message: "<%= inspect value %> doesn't count as accepted")
{:error, "nil doesn't count as accepted"}