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Tutorial Part 8. Validations

Types of Validation

• length Length validation. An integer for a max length or a list of two elements for '(min max) length.
• format Format validation. Either one of :alpha, :alnum, :integer, :email, :date, :image, regexp as a string, a function or nil.
• member Member validation. A list of valid input options.
• required Required validation. A value is required if this is non nil.
• unique Uniquness validation. A slot value of a persistent class must be unique if this is non nil.

Validating a value

validation-errors

Syntax:

(validation-errors label value validators)

validation-errors validates VALUE with VALIDATORS and returns error messages if any. LABEL is used as a subject of error messages.

Examples:

(validation-errors "label" nil '(:required t :length 3))
;=> ("label can't be empty") 

(validation-errors "label" "12345" '(:required t :length 3))
;=> ("label is too long (maximum is 3 characters)") 

with-validations

Syntax:

(with-validations validations error-handler body)

with-validations executes VALIDATIONS. Then executes ERROR-HANDLER if there is any error and BODY otherwise. The ERROR-HANDLER takes one argument which is a list of validation error messages.

Examples:

(with-validations (("1" "v" '(:required t))
                   ("2" nil '(:required t)))
  (lambda (e) e)
  "ok") ;=> ("2 can't be empty")

(with-validations (("1" "v" '(:required t))
                   ("2" "v" '(:required t)))
  (lambda (e) e)
  "ok") ;=> "ok"

slot-validation-errors

Syntax:

(slot-validation-errors class slot &optional instance)

slot-validation-errors validates posted parameters to edit the SLOT value in the persistent CLASS and returns a list of error messages if any. INSTANCE is an instance of the persistent CLASS only needed to update an existing instance.

Examples:

(defpclass blog ()
  ((body :required t)))

(with-post-parameters '(("blog_body" . nil))
  (slot-validation-errors 'blog (get-slot 'blog 'body)))

;=> ("Body can't be empty") 

class-validation-errors

Syntax:

(class-validation-errors class &optional instance)

class-validation-errors validates posted parameters to make/update an instance of the persistent CLASS and returns a list of error messages if any. INSTANCE is an instance of the persistent CLASS only needed to update an existing instance.

Examples:

(defpclass blog ()
  ((title :required t)
   (body  :required t)))

(with-post-parameters '(("blog_title" . nil)
                        ("blog_body"  . nil))
  (class-validation-errors 'blog))

;=> ("Title can't be empty" "Body can't be empty") 

Validation error messages

You can change the validation error messages by changing the value of *validation-error-messages* or redefining the error-msg function.