Based on Om Input

You just go down the list of all the most important things on the internet and what you find is :
a Form is usually the broker for the stuff that matters

Luke Wroblewski from Conversions@Google 2014 - Part 2

• Generate forms with specification using Prismatic/Schema.
• Provide best practice UX
• Use no external JS Framework dependencies beside React.js
• Unified client/server validation

To build a component we need :

• A name ;
• A description of the fields ;
• A callback function to use the data ;
• Options to customize the component.

The name is used :

• as the React.js display name;
• To differentiate components in the UI.

The fields of a component are described with Schema.

Using Schema allows the :

• Validation of the data ;
• Coercion of String to proper types.

• s/Str
• s/Int
• s/Inst
• s/enum
• s/Bool
• s/Eq
• s/Regex

A value can be nil using s/maybe :

{:person-first-name (s/maybe s/Str)}

A key can be optional using s/s/optional-key :

 {(s/optional-key :person-size) s/Num}

(def sch-person {:person-first-name s/Str
                 :person-name s/Str
                 (s/optional-key :person-birthdate) s/Inst
                 (s/optional-key :person-size) s/Int
                 (s/optional-key :person-gender) (s/enum "M" "F")})

To build an input component, just call the function make-input-comp with the required parameters :

• A keyword for the component name
• A Prismatic/Schema
• a callback function

In this example we build the component :create-person with the Schema seen previously and the callback simply diplay the created map :

(def person-input-view (make-input-comp :create-person sch-person #(js/alert %)))

Each entry of a schema generate a field in the form.

Hence, the example schema will produce a form with these input fields :

• A mandatory input of type text for :person-first-name ;
• A mandatory input of type text for :person-name ;
• An optional date input for the :person-birthdate ;
• An optional input that allows only Integer for :person-size ;
• An optional select that that present the choices "M" and "F" ;
• A validation button that trigger the callback.

There are two type of validations :

1. Schema validation
2. Verily validation

Schema is able to check that a data structure is conform :

In case of a map :

• all required keys are present ;
• All values are of the correct type ;

This job is done by Schema/Coercion : When a value is not of the declared type, we have a chance to coerce it in the correct type.

The problem with an HTMl form is that all data are strings.

• An empty string represents nil
• Other types must be coerced to the correct type : s/Num, s/Int, s/Inst

• A required input must have a non blank value ;
• A coercion appends if needed for type different than s/Str

Options are a mean to override the default behavior of the library.

All options are given in a map.

The schema is a map that can't be ordered so the fields are displayed in a random order.

You can define the total ordering by giving a vector :

(def opts {:order [:person-first-name :person-name :person-gender :person-birthdate :person-size :person-married]})

By default the enum is display as a dropdown list It is possible to choose different representations : Vertical Group of radio buttons :

(def opts {:person-gender {:type "radio-group"}})

Horizontal group of radio buttons :

(def opts {:person-gender {:type "radio-group-inline"}})

Segmented controls :

(def opts {:person-gender {:type "btn-group"}})

Stepper (-|+) :

(def opts {:items/number {:type "stepper"
                          :attrs {:min 0 :max 10 :step 1}}})

It is possible to add more complex validation rules than the one provided by Schema.

I chose Verily for the following reasons :

• the rules can be described as data structure
• the rules are expressed on the whole map not by key.
• It works for Clojure and ClojureScript.

(def opts {:validations [[:min-val 100 :person-size :person-size-min-length]
                         [:email :person-email :bad-email]]})

It should be possible to have initial values for each field.

(def opts {:init {:person-married true}})

The initial data could be retrieved from the cursor app-state.

Copyright © 2013-2015 Hiram Madelaine and David Pollak

Licensed under the EPL (see the file LICENSE.md).