Ngx Schema Form

Ngx Schema Form is an Angular 2+ module allowing you to instanciate an HTML form from a JSON schema.

Note: Version 1.x is compliant with Angular <=4, version 2.x is compliant with Angular >=6.

DISCLAIMER

Ngx 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

Demo

Features

• Generate a form from a single json schema object
• Generate a form from a default set of html constructs
• Allow initialization from previous values
• Validation handled by z-schema
• Allow injection of custom validators
• Allow declaration of custom widgets
• Allow injection of custom bindings (new!)

Installation

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

npm install ngx-schema-form --save

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

JSON Schema

With the installation there comes a JSON-Schema file that declares all specific or additional properties supported by ngx-schema-form.

When using *.json files you may declare it with the $schema property to let your IDE's autocompletion help you create a schema-form.

{
  "$schema": "./node_modules/ngx-schema-form/ngx-schema-form-schema.json",
  "title": "My awesome schema-form"
  ...
}

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.

// 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: '<sf-form [schema]="mySchema"></sf-form>'
})

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 Ngx schema form.

//app.module.ts

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

@NgModule({
  imports: [
    SchemaFormModule.forRoot(),
    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.

Accessing the form's value

Input binding

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

@Component({
template: '<sf-form [schema]="mySchema" [model]="myModel"></sf-form>'
})
export class AppComponent {
  mySchema = {...};
  myModel = {email:" [email protected]"};
}

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:

template: '<sf-form [schema]="mySchema" (onChange)="value=$event.value"></sf-form>{{value | json}}'

The model property allow two-way data binding:

<sf-form [schema]="mySchema" [(model)]="value"></sf-form>{{value | json}}

Widgets

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:

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:

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 ):

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

Default widget's registry

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:

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

Actions and buttons

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

// app.component.ts
@Component({
  selector: "minimal-app",
  // Bind the actions map to the the "actions" input
  template: '<sf-form [schema]="mySchema" [actions]="myActions"></sf-form>'
})
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() }
  }
}

Render buttons

You may define you own widget to create buttons by overriding the default widget for action buttons or create completely customized button widgets.

Override

Override the default action button widget in your WidgetRegistry implementation and register your own button widget.

    this.register('button', MyButtonWidgetComponent);

Custom

Define a custom button widget by setting the property button.widget in the schema

  "password": {
    "type": "string",
    "description": "Password",
    "buttons": [
      {
        "id": "reset",
        "label": "Reset"
      },
      {
        "id": "custom_b",
        "label": "My custom button",
        "widget": "my_custom_button" // custom widget name for this button
      }
    ]
  }

and then register it in your WidgetRegistry implementation

    this.register('my_custom_button', MyCustomButtonWidgetComponent);

Binding

The button widget will get provided the button object form the schema including the button.action from the action registry and the formProperty object.

To be fully AOT compatible the custom button widget may then extend ButtonWidget or provide the properties button and formProperty by it self.

  import {Component} from "@angular/core";
  import {ButtonWidget} from 'ngx-schema-form/dist/defaultwidgets'
  
  @Component({
    selector: 'sf-button-widget',
    templateUrl: 'custom-button.widget.html'
  })
  export class CustomWidgetComponent extends ButtonWidget {
  
  }

  @Component({
    selector: 'sf-button-widget',
    templateUrl: 'custom-button.widget.html'
  })
  export class CustomWidgetComponent {
    public button
    public formProperty
  }

Advanced validation

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:

@Component({
  selector: "minimal-app",
  // Bind the validator map to the the "validators" input
  template: '<sf-form [schema]="mySchema" [validators]="myValidators"></sf-form>'
})
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) => {
      const passwordProperty = formProperty.findRoot().getProperty('password')
      if (passwordProperty.value !== undefined && property.valid && value !== passwordProperty.value) {
        return { "passwordCheck": { "expectedValue": "same as 'password'" } }
      }
      return null;
    }
  }
}

Custom Bindings

Some form field may require a reaction to other forms fields when getting some input. The Form component accepts a bindings input bound to a map of field paths mapped to event and binding functions.
The binding function takes two arguments: the native event, and the property corresponding to it.

The following example creates a form where you will fill in some data for a family. When you type in the name of the parent (first person) the name of the children will be kept updated.

@Component({
  selector: "minimal-app",
  // Bind the bindings map to the the "bindings" input
  template: '<sf-form [schema]="mySchema" [bindings]="myFieldBindings"></sf-form>'
})
export class AppComponent {
  mySchema = 
  {
               "type": "object",
               "title": "Example with custom bindings.",
               "description": "Type a family name to see how the name gets synchronized with the children.",
               "properties": {
                 "name": {
                   "type": "string",
                   "title": "Surname"
                 },
                 "forename": {
                   "type": "string",
                   "title": "Forename"
                 },
                 "children": {
                   "type": "array",
                   "title": "Family",
                   "items": {
                     "type": "object",
                     "title": "Children",
                     "properties": {
                       "name": {
                         "type": "string",
                         "title": "Surname"
                       },
                       "forename": {
                         "type": "string",
                         "title": "forename"
                       },
                       "age": {
                         "type": "number",
                         "title": "age"
                       }
                     }
                   }
                 }
               }
             }

  // Declare a mapping between field and event-id
  myFieldBindings = {
      '/name': [
        {
          'input': (event, formProperty: FormProperty) => {
            const parent: PropertyGroup = formProperty.findRoot();

            /**
             * Set the input value for the children
             */
            const child1: FormProperty = parent.getProperty('children/0/name');

            child1.setValue(formProperty.value, false);

            const child2: FormProperty = parent.getProperty('children/1/name');
            child2.setValue(event.target.value, false);

            /**
             * Get the input value for all the children
             */
            for (const objectProperty of parent.getProperty('children').properties) {
              console.log('Value for child ', objectProperty, objectProperty.properties['name'].value);
            }
          }
        }
      ]
    };
}

Conditional fields

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.

Value
The value to match is set as array item.
Setting multiple items will make the visiblity condition true if one of the values matches.
If it is required to match all values head over to the section visibleIf with allOf condition.

$ANY$
Adding the value $ANY$ to the array of conditional values, will make the field visible for any value inserted.

@Component({
  selector: "minimal-app",
  template: '<sf-form [schema]="mySchema"></sf-form>'
})
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"]
  }
}

$EMPTY$
Assigning an empty Object to 'visibleIf' is interpreted as visibleIf nothing, thereby the widget is hidden and not present in model.

mySchema = {
    "properties": {
      "hidden": {
        "type": "boolean",
        "visibleIf": { }
      }
    }
  }

visibleIf may also declare conditional binding by using oneOf or allOf properties. Where oneOf is handled as OR and allOf is handled as AND.

  "visibleIf": {
        "allOf": [
          {
            "forename": [
              "$ANY$"
            ]
          },
          {
            "name": [
              "$ANY$"
            ]
          }
        ]
      }

The oneOf a is prioritized before the allOf and both are prioritized before the property binding.

oneOf and allOf oneOf and allOf are reserved keywords and not suitable as property names

Arrays

To address array items or not yet existing properties the visibleIf condition path may contain wildcard *.

e.g

  "visibleIf": {
        "oneOf": [
          {
            "/person/*/age": [
              "18"
            ]
          }
        ]
      }

To address a specific item the visibleIf condition path should contain the index position.

e.g

  "visibleIf": {
        "oneOf": [
          {
            "/person/1/age": [
              "18"
            ]
          }
        ]
      }

Expressions

Expressions allow a more complex visibleIf condition related to the involded fields.
To use an expression the value of the item
in the conditional array must start with $EXP$.
When processing the expression a context is available containing
a source and a target object.
Where source is the FormProperty that has the visibleIf condition defined
and target is the FormProperty that has been defined by the path.

  "myField" : { // SOURCE
    "visibleIf": {
          "oneOf": [
            {
              "/person/1/age": // TARGET
              [
                "$EXP$ target.value < 18"
              ]
            }
          ]
        }
   }

Hidden fields

When a field has been made invisible by the condition visibleIf then the property of the invisible field will be missing in the result model.

If there is need to submit default values that are not visible for the form the widget.id hidden might be the better choice

  mySchema = {
    "properties": {
      "hiddenInput": {
        "type": "boolean",
        "widget": "hidden",
        "default": true
      },
      "lastName": {
        "type": "string",
        ...
      }
    }
  }

so the value of the hidden field will be bound to the output model

  {
    "hiddenInput": true,
    "lastName": "Doe",
    ...
  }

Fields presentation and ordering

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:

{
  "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:

{
  "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:

@Component({
  selector: 'plone-view-edit',
  template: '<sf-form [schema]="schema" [model]="model" [actions]="actions"></sf-form>'
})
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

Ngx 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:

@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):

<mdl-textfield [label]="schema.description" type="string" floating-label 
    [name]="name" [attr.readonly]="schema.readOnly?true:null"
    [attr.id]="id"
    [attr.disabled]="schema.readOnly?true:null"
    [formControl]="control"></mdl-textfield>

And you need to declare it in a custom registry:

import { MyStringWidget } from './mystring';

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

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

And, in your module, you need to:

• declare your widget component (like any regular component),
• declare it as an entry components (it means it can be instanciated dynamically),
• and provide your registry.

declarations: [MyStringWidget],
entryComponents: [MyStringWidget],
providers: [{provide: WidgetRegistry, useClass: MyWidgetRegistry}],

Note: you will also need to import ReactiveFormsModule if you want to be able to use form control:

import { ReactiveFormsModule } from '@angular/forms';
...
@NgModule({
  ...
  imports: [
    ...
    ReactiveFormsModule,
  ]
})

Create form from html instead of json schema

Ngx schema form allows you to create forms from angular html templates too. For this you only need to import TemplateSchemaModule to your app, and use the directive templateSchema on sf-form.

The followin html will generate the same form as the json schema in getting started section.

<sf-form  [(ngModel)]="model"  templateSchema >
  <sf-field name="email" format="email" [required]="true"> Email </sf-field>
  <sf-field name="password" widget="password" [required]="true"> Password </sf-field>
  <sf-field name="rememberMe" type="boolean"> Remember Me </sf-field>
</sf-form>

For more details see example app.

Development and build

To work on this package:

npm install

Then you can build:

npm run build:lib

If you want to work with the demo:

npm install -g @angular/cli
npm install
ng build schema-form
npm start

Building the API documentation

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

npm run typedoc

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