Custom Validation Message

When using Rails validations, a standard error message will be provided whenever there is a violation. Consider the scenario when there is a uniqueness validation on the email attribute and it is violated:

# User model
validates_uniqueness_of :email

# Users controller
new_user.errors.full_messages
#=> ["Email has already been taken"]

Sometimes you don't want the default validation message. The validation declaration can be given a message option to specify an alternate validation message.

# User model
validates_uniqueness_of :email, message: 'is not available'

# Users controller
new_user.errors.full_messages
#=> ["Email is not available"]

Keep in mind that full_messages will prepend the model name to the front of the message. You'll want to ensure that the resulting message is coherent.