Angular2 Schema Form 

Angular2 Schema Form is an Angular2 module allowing you to instanciate an HTML form from a JSON schema.

DISCLAIMER

Angular2 Schema Form is not related to angular-schema-form and schemaform.io.

We think angular-schema-form is a great Angular 1 library, and when it will move to Angular 2, we will probably join our efforts to produce and maintain a unique Angular 2 solution.

Demo

There is an example of application using Angular2 Schema Form.
You can also test the module on the website.

Features

* Generate a form from a single json schema object
* Allow initialization from previous values
* Validation handled by z-schema
* Allow injection of custom validators
* Allow declaration of custom widgets

Installation

To use Angular2 Schema Form in your project simply execute the following command:

``bash
npm install angular2-schema-form --save
`

You just have to check that all the peer-dependencies of this module are satisfied in your package.json.

Getting started

Here our goal will be to create a simple login form.
Let's start by creating a simple AppComponent taking a simple JSON schema as input.

`js
// app.component.ts

import { Component } from "@angular/core";

@Component({
selector:"minimal-app",
// Bind the "mySchema" member to the schema input of the Form component.
template: ''
})

export class AppComponent {
// The schema that will be used to generate a form
mySchema = {
"properties": {
"email": {
"type": "string",
"description": "email",
"format": "email"
},
"password": {
"type": "string",
"description": "Password"
},
"rememberMe": {
"type": "boolean",
"default": false,
"description": "Remember me"
}
},
"required": ["email","password","rememberMe"]
}
}
`

Create a module which import the AppComponent and configure Angular2 schema form.
`js
//app.module.ts

import { NgModule } from "@angular/core";
import { BrowserModule } from "@angular/platform-browser";
import { SchemaFormModule, WidgetRegistry, DefaultWidgetRegistry } from "angular2-schema-form";
import { AppComponent } from "./app.component";

@NgModule({
imports: [
SchemaFormModule,
BrowserModule
],
declarations: [AppComponent],
providers: [{provide: WidgetRegistry, useClass: DefaultWidgetRegistry}]
})
export class AppModule {}
`

The code above creates a form with three required fields.
The validation state of each field is reflected by the class of each of them which can be either "has-error" or "has-success".
Validation is done everytime a field's value changes.
Basic validation is made by testing the value of the field against its corresponding schema.
The input schema support almost all the features listed on the JSON schema specification.

$3

#### Input binding
It is possible to provide initial values to the form.
You can set the initial form's value through the model input:


`js
@Component({
template: ''
})
export class AppComponent {
mySchema = {...};
myModel = {email:" john.doe@example.com"};
}
`

#### Output binding
The Form component provides the onChange output binding of which value represents the value of the form.
For instance, you can display the current forms's value with the following template:

`js
template: '{{value | json}}'
`

$3


Each field can be displayed using a specific widget.
To declare the widget you want to use, add its id to the field's definition:

`js
mySchema = {
"properties": {
"email": {
"type": "string",
"description": "email",
"format": "email"
},
"password": {
"type": "string",
"description": "Password",
"widget": "password"// == "widget": {"id": "password"}
},
"rememberMe": {
"type": "boolean",
"default": false,
"description": "Remember me"
}
}
}
`

If there is no widget declared in a given property's schema, its type is used as widget id and the default registry gives a default widget (see details below).
For instance, a string property will use the "string" widget.
The following JSON schema is equivalent with the above example:

`js
mySchema = {
"properties": {
"email": {
"type": "string",
"description": "email",
"format": "email",
"widget": "string"
},
"password": {
"type": "string",
"description": "Password",
"widget": "password"// == "widget": {"id": "password"}
},
"rememberMe": {
"type": "boolean",
"default": false,
"description": "Remember me",
"widget": "boolean"
}
}
}
`

Some widgets accept parameters as input, in such cases, it is possible to provide them in the schema directly within the widget property (here the TinyMCE widget ):

`js
mySchema = {
"properties": {
"pageContent": {
"type": "string",
"description": "Page content",
"widget": {
"id": "richtext",
"plugins": "textcolor colorpicker",
"toolbar": "forecolor backcolor"
}
}
}
}
`

$3


Available widgets are managed through a WidgetRegistry.
The default registry (DefaultWidgetRegistry) contains many widgets listed below, ordered by type:

- string: string, search, tel, url, email, password, color, date, date-time, time, textarea, select, file, radio, richtext
- number: number, integer, range
- integer: integer, range
- boolean: boolean, checkbox

Note that the select and radio widgets rely on the oneOf property:

`js
"operatingSystem": {
"type": "string",
"oneOf":[{
"enum": ["linux"],
"description": "GNU/Linux"
}, {
"enum": ["osx"],
"description": "OSX"
}, {
"enum": ["windows"],
"description": "Windows"
},{
"enum": ["other"],
"description": "Other"
}],
"default": "other"
}
`

$3

Each schema can be extended by adding buttons after its widget.

`js
// app.component.ts
@Component({
selector:"minimal-app",
// Bind the actions map to the the "actions" input
template: ''
})
export class AppComponent {
// The schema that will be used to generate a form
mySchema = {
"properties": {
"email": {
"type": "string",
"description": "email",
"format": "email"
},
"password": {
"type": "string",
"description": "Password",
"buttons": [{
"id": "reset",
"label": "Reset"
}]
},
"rememberMe": {
"type": "boolean",
"default": false,
"description": "Remember me"
}
},
"required": ["email","password","rememberMe"],
"buttons": [{
"id": "alert", // the id of the action callback
"label": "Alert !" // the text inside the button
}]
}

// Declare a mapping between action ids and their event listener
myActions = {
"alert": (property) => {alert(JSON.stringify(property.value))},
"reset": (property) => {property.reset()}
}
}
`

$3


JSON schema provides validation against a static schema but its often necessary to provide other validation rules.
The Form component accepts a validators input bound to a map between a field id and a validation function.
The validation function takes three arguments: the value of the field, the property corresponding to it and the form object.

In the following example we create a simple registration form.
The user have to enter his password twice.
To perform this check we create a custom validator:

`js
@Component({
selector:"minimal-app",
// Bind the validator map to the the "validators" input
template: ''
})
export class AppComponent {
mySchema = {
"properties": {
"email": {
"type": "string",
"description": "email",
"format": "email"
},
"password": {
"type": "string",
"description": "Password"
},
"passwordCheck": {
"type": "string",
"description": "Password (verification)"
}
},
"required": ["email", "password", "passwordCheck"]
}

// Declare a mapping between action ids and their implementations
myValidators = {
"/passwordCheck": (value, property, form) => {
if (controls.password !== undefined
&& controls.password.valid
&& value !== values.password
) {
return {"passwordCheck":{"expectedValue":"same as 'password'"}}
}
return null;
}
}
}
`

$3


It is possible to make the presence of a field depends on another field's value.
To achieve this you just have to add a visibleIf property to a field's definition.
Adding the value $ANY$ to the array of conditional values,will make the field visible for any value inserted.

`js
@Component({
selector:"minimal-app",
template: ''
})
export class AppComponent {
mySchema = {
"properties": {
"name": {
"type": "string",
"description": "Username"
},
"comment": {
"type": "string",
"description": "Comment"
},
"registerNewsletter": {
"type": "boolean",
"description": "I want to receive the newsletter",
"default": false,
"visibleIf": {
"comment": ['$ANY$']
}
},
"registerEmail": {
"type": "string",
"description": "Email",
"format": "email",
// Declare that this field must be displayed only if registerNewsletter is true
"visibleIf": {
"registerNewsletter": [true]
}
}
},
"required": ["name","comment","registerToNewsletter"]
}
}
`

$3


As a JSON object is an unordered collection you can't be sure your fields will be correctly ordered when the form is built.
The order and fieldsets entries of the schema are here to organize your fields.

#### Ordering
The order entry is an array listing all the fields ids in the order they must appear in the form:

`js
{
"properties": {
"firstName": {"type": "string","description": "First name"},
"lastName": {"type": "string","description": "Last name"},
"email": {"type": "string","description": "Email"}
},
"order": ["firstName", "lastName", "email"]
}
`

#### Fieldsets
With the fieldsets property, you can describe the different parts of the form and the fields they contain:

`js
{
"properties": {
"firstName": {"type": "string","description": "First name"},
"lastName": {"type": "string","description": "Last name"},
"email": {"type": "string","description": "Email"},
"notificationsFrequency": {
"type":"string",
"description": "Notifications frequency",
"widget": "select",
"oneOf": [{
"description": "Daily", "enum": ["daily"]
}, {
"description": "Weekly", "enum": ["weekly"]
}, {
"description": "Monthly", "enum": ["monthly"]
}],
"default": "daily"
}
},
"fieldsets": [{
"title": "Personal information",
"fields": ["firstName", "lastName", "email"]
}, {
"title": "Account settings",
"fields": ["notificationsFrequency"]
}]
}
`

The title entry of each fieldset is optional.

Fixing the schema or model before rendering

Sometimes your schema (or model) is provided by a backend you cannot control.
If it is not formatted the way Angular 2 Schema Form expects or if some elements are missing (for instance the fieldsets, some widgets, etc.), you can fix it very easily in your component:

`javascript
@Component({
selector: 'plone-view-edit',
template: ''
})
export class MyComponent {
private schema:any =
'properties': {}
};
private actions:any = {};
private model:any = {};

constructor(private http: Http) { }

ngOnInit() {
this.http.get('http://mybackend/schema').subscribe(res => {
let schema = res.json();

// FIXES
// the "description" field must be rendered with tinymce
schema.properties.description.widget = 'tinymce'

// the "publication" field is required
schema.required = ['publication'];

this.schema = schema;
});
}
}
`

Creating a custom widget

Angular2 schema form allows you to create your own widget.

Note: Currently this feature is not completely defined and the API might change.

You need to derivate the widget you want to customize:
`javascript
@Component({
selector: 'mdl-sf-string-widget',
templateUrl: './string.widget.html'
})
export class MyStringWidget extends StringWidget {}
`

You need to provide its html template (let's imagine we want to use the Material Design text field):
`html
[name]="name" [attr.readonly]="schema.readOnly?true:null"
[attr.id]="id"
[attr.disabled]="schema.readOnly?true:null"
[formControl]="control">
`

And you need to declare it in a custom registry:
`javascript
import { MyStringWidget } from './mystring';

export class MyWidgetRegistry extends DefaultWidgetRegistry {
constructor() {
super();

this.register('string', MyStringWidget);
}
}
`

And then you need to provide your registry in your module:
`javascript
providers: [{provide: WidgetRegistry, useClass: MyWidgetRegistry}],
`

Note: you will also need to import ReactiveFormsModule if you want to be able to use form control:
`javascript
import { ReactiveFormsModule } from '@angular/forms';
...
@NgModule({
...
imports: [
...
ReactiveFormsModule,
]
`

Development and build

To work on this package:

`bash
npm install
`

You also need the peer dependencies:

`bash
npm run install:peers
`

Then you can build:

`bash
npm run build
`

If you want to work with the demo:

`bash
npm install -g @angular/cli
cd ./tests
npm install
cd ./src/app
ln -s ../../../src/
cd -
ng serve
`

Building the API documentation

You can build an HTML version of the API documentation by running the following command:

`bash
npm run typedoc
``

The api is then available in the "doc" directory.