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angular2-json-schema-form

Angular JSON Schema Form

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A JSON Schema Form builder for Angular 4, similar to, and mostly API compatible with,

Note: This is currently a personal proof-of-concept project, and is NOT affiliated with any of the organizations listed above. (Though they are all awesome, and totally worth checking out.)

Check out the live demo and play with the examples

Check out some examples here.

This example playground features over 70 different JSON Schemas for you to try (including all examples used by each of the three libraries listed above), and the ability to quickly view any example formatted with Material Design or Bootstrap 3, or without any formatting.

Installation

To install from GitHub

To install the library and the example playground from GitHub, clone https://github.com/dschnelldavis/angular2-json-schema-form.git with your favorite git program. Or, assuming you have git and Node/NPM installed, enter the following in your terminal:

git clone https://github.com/dschnelldavis/angular2-json-schema-form.git angular2-json-schema-form
cd angular2-json-schema-form
npm install
npm start

This should start a server with the example playground, which you can view in your browser at http://localhost:4200

All the source code is in the /src folder. Inside that folder, you will find the following sub-folders:

  • lib/src - Angular JSON Schema Form main library
  • lib/src/framework-library - framework library
  • lib/src/widget-library - widget library
  • lib/src/shared - various utilities and helper functions
  • demo - the demonstration playground example application
  • demo/assets/example-schemas - JSON Schema examples used in the playground

If you want detailed documentation describing the individual functions used in this library, run npm run docs to generate TypeDoc documentation, and then look in the newly generated /docs folder. (Angular JSON Schema Form is still a work in progress, so right now this documentation varies from highly detailed to completely missing.)

To install from NPM and use in your own project

If, after playing with the examples, you decide this library is functional enough to use in your own project, you can install it from NPM using either NPM or Yarn. To install with NPM, run the following from your terminal:

npm install angular2-json-schema-form --save
npm install @angular/cdk --save
npm install @angular/flex-layout --save
npm install @angular/material --save

IMPORTANT NOTE ABOUT PEER DEPENDANCIES: For now, Angular Material is a required peer dependency for the current version. This will be fixed in a future version, which will offer separate installers for the Bootstrap and Material Design frameworks. But until that happens, even if you don't intend to use Angular Material framework, you may need to install Angular Material and its related modules through NPM for your project to build correctly. If you want to try building your project, go ahead, and depending on your build process it might work. But if your build fails, chances are you need to install these other libraries to make angular2-json-schema-form work.

Then import JsonSchemaFormModule in your main application module:

import { JsonSchemaFormModule } from 'angular2-json-schema-form';

If you want to use the Material Design framework, also add:

import { FlexLayoutModule }                   from '@angular/flex-layout';
import { MaterialModule, MdDatepickerModule } from '@angular/material';

If you don't want to use the Material Design framework, you don't need to import these modules. (To get the project to build correctly, you may need to install the Angular Material libraries through NPM, as described above, but you don't need to actually import them.)

Finally, edit the imports array in your @NgModule declaration to add JsonSchemaFormModule, and the Angular Material modules if you want to use that framework.

Your final app.module.ts should look something like this:

import { BrowserModule }                      from '@angular/platform-browser';
import { NgModule }                           from '@angular/core';
import { FlexLayoutModule }                   from '@angular/flex-layout';
import { MaterialModule, MdDatepickerModule } from '@angular/material';
 
import { JsonSchemaFormModule }               from 'angular2-json-schema-form';
 
import { AppComponent }                       from './app.component';
 
@NgModule({
  declarations: [ AppComponent ],
  imports:      [
    BrowserModule, FlexLayoutModule, MaterialModule,
    MdDatepickerModule, JsonSchemaFormModule
  ],
  providers:    [],
  bootstrap:    [ AppComponent ]
})
export class AppModule { }

Additional notes for Angular CLI

Make sure you are running the latest version of Angular CLI.

Older versions of Angular CLI (e.g. 1.0.1) may fail with the error Critical dependency: the request of a dependency is an expression while trying to compile ajv (Another JSON Schema Validator). But this error has been fixed in newer versions. So if you receive that error, just upgrade your Angular CLI to the latest version.

Additional notes for SystemJS

If you use SystemJS, you will also need to make the following changes to your systemjs.config.js file. (If you're using a recent version of Angular CLI, or you don't have a systemjs.config.js file in your project, that means you're not using SystemJS, and you can safely ignore this section.)

Add these lines to the 'map' section of systemjs.config.js, if they do not already exist:

'@angular/animations':       'npm:@angular/animations/bundles/animations.umd.js',
'@angular/material':         'npm:@angular/material/bundles/material.umd.js',
'angular2-json-schema-form': 'npm:angular2-json-schema-form/bundles/angular2-json-schema-form.umd.js',
'ajv':                       'npm:ajv/dist/ajv.min.js',
'lodash':                    'npm:lodash/lodash.min.js'

Using Angular JSON Schema Form

Basic use

For basic use, after loading the JsonSchemaFormModule as described above, to add a form to your Angular component, simply add the following to your component's template:

<json-schema-form
  [schema]="yourJsonSchema"
  (onSubmit)="yourOnSubmitFn($event)">
</json-schema-form>

Where the schema input is a valid JSON schema object (v3 or v4), and the onSubmit output calls a function to process the submitted form data, which will be passed as a JSON object. If you don't already have your own schemas, you can find a whole bunch of samples to test with in the src/demo/assets/example-schemas folder, as described above.

Advanced use

Additional inputs an outputs

For more control over your form, you may provide these additional inputs:

  • layout - array with a custom form layout (see Angular Schema Form's form definitions for information about how to construct a form layout)
  • data - object to populate the form with default or previously submitted values
  • options - object to set any global options for the form
  • widgets to add custom widgets
  • framework - string or object to set which framework to use set to 'material-design' (the default), 'bootstrap-3', 'no-framework', or pass in your own custom framework object

If you want more detailed output, you may provide additional functions for onChanges to read the values in real time as the form is being filled out, and you may implement your own custom validation indicators from the boolean isValid or the detailed validationErrors outputs.

Here is an example:

<json-schema-form
  [schema]="yourJsonSchema"
  [layout]="yourJsonFormLayout"
  [data]="yourData"
  [options]="yourGlobalOptionSettings"
  [widgets]="yourCustomWidgets"
  framework="bootstrap-3"
  loadExternalAssets="true"
  (onChanges)="yourOnChangesFn($event)"
  (onSubmit)="yourOnSubmitFn($event)"
  (isValid)="yourIsValidFn($event)"
  (validationErrors)="yourValidationErrorsFn($event)">
</json-schema-form>

(Note: The loadExternalAssets attribute may be useful when you are first trying out this library, but do not use it in production sites - instead separately load any required assets. For full details see 'Changing or adding frameworks', below.)

Single-input mode

You may also combine all your inputs into one compound object and include it as a form input, like so:

let yourCompoundInputObject = {
  schema:    { ... },  // required
  layout:    [ ... ],  // optional
  data:      { ... },  // optional
  options:   { ... },  // optional
  widgets:   { ... },  // optional
  framework: { ... }   // optional
}
<json-schema-form
  [form]="yourCompoundInputObject"
  (onSubmit)="yourOnSubmitFn($event)">
</json-schema-form>

You can also mix these two styles depending on your needs. In the example playground, all examples use the combined form input for schema, layout, and data, which enables each example to control those three inputs, but the playground uses another input for framework, enabling you to change the framework separately from the example.

Combining inputs is useful if you have many unique forms and store each form's data and schema together. If you have one form (or many identical forms), it will likely be more useful to use separate inputs for your data and schema—though even in that case, if you use a custom layout, you could store your schema and layout together and use one input for both.

Data-only mode

Angular JSON Schema Form can also create a form entirely from a JSON object—with no schema—like so:

exampleJsonObject = {
  "first_name": "Jane", "last_name": "Doe", "age": 25, "is_company": false,
  "address": {
    "street_1": "123 Main St.", "street_2": null,
    "city": "Las Vegas", "state": "NV", "zip_code": "89123"
  },
  "phone_numbers": [
    { "number": "702-123-4567", "type": "cell" },
    { "number": "702-987-6543", "type": "work" }
  ], "notes": ""
};
<json-schema-form
  [data]="exampleJsonObject"
  (onSubmit)="yourOnSubmitFn($event)">
</json-schema-form>

In this mode, Angular JSON Schema Form generates a schema from your data on the fly. The generated schema is relatively simple, compared to what you could create on your own. However, as the above example shows, it does detect and enforce string, number, and boolean values (nulls are also assumed to be strings), and automatically allows array elements to be added, removed, and reordered.

After displaying a form in this mode, you can also use the formSchema and formLayout outputs (described in 'Debugging inputs and outputs', below), to return the generated schema and layout, which will give you a head start on writing your own schemas and layouts by showing you examples created from your own data.

Compatibility modes

If you have previously used another JSON form creation library—Angular Schema Form (for AngularJS), React JSON Schema Form, or JSON Form (for jQuery)—in order to make the transition easier, Angular JSON Schema Form will recognize the input names and custom input objects used by those libraries. It should automatically work with JSON Schemas in version 6, version 4, version 3, or the truncated version 3 format supported by JSON Form. So the following will all work:

Angular Schema Form (AngularJS) compatibility:

<json-schema-form
  [schema]="yourJsonSchema"
  [form]="yourAngularSchemaFormLayout"
  [model]="yourData">
</json-schema-form>

React JSON Schema Form compatibility:

<json-schema-form
  [schema]="yourJsonSchema"
  [UISchema]="yourReactJsonSchemaFormUISchema"
  [formData]="yourData">
</json-schema-form>

JSON Form (jQuery) compatibility:

<json-schema-form
  [form]="{
    schema: yourJsonSchema,
    form: yourJsonFormLayout,
    customFormItems: yourJsonFormCustomFormItems,
    value: yourData
  }">
</json-schema-form>

Debugging inputs and outputs

Finally, Angular JSON Schema Form includes some additional inputs and outputs for debugging:

  • debug input—activates debugging mode
  • loadExternalAssets input—automatically loads external JavaScript and CSS needed by the selected framework (this is not 100% reliable, so while this may be helpful during development and testing, it is not recommended for production)—Note: If you are using this mode and get a console error saying an external asset has not loaded (such as jQuery, required for Bootstrap 3) simply reloading your web browser will usually fix it
  • formSchema and formLayout outputs—returns the final schema and layout used to create the form (which will either show how your original input schema and layout were modified, if you provided inputs, or show you the automatically generated ones, if you didn't)
<json-schema-form
  [schema]="yourJsonSchema"
  [debug]="true"
  [loadExternalAssets]="true"
  (formSchema)="showFormSchemaFn($event)"
  (formLayout)="showFormLayoutFn($event)">
</json-schema-form>

Customizing

Angular JSON Schema Form has two built-in features designed to make it easy to customize at run-time: a widget library and a framework library. All forms are constructed from these basic components. The default widget library includes all standard HTML 5 form controls, as well as several common layout patterns, such as multiple checkboxes and tab sets. And the default framework library includes templates to style forms using either Bootstrap 3 or Material Design (or with no formatting, which is not useful in production, but can be helpful for debugging).

Changing or adding widgets

To add a new widget or override an existing widget, either add an object containing your new widgets to the widgets input of the <json-schema-form> tag, or load the WidgetLibraryService and call registerWidget(widgetType, widgetComponent), with a string type name and an Angular component to be used whenever a form needs that widget type.

Example:

import { YourInputWidgetComponent } from './your-input-widget.component';
import { YourCustomWidgetComponent } from './your-custom-widget.component';
...
let yourNewWidgets = {
  input: YourInputWidgetComponent,          // Replace existing 'input' widget
  custom-control: YourCustomWidgetComponent // Add new 'custom-control' widget
}

...and...

<json-schema-form
  [schema]="yourJsonSchema"
  [widgets]="yourNewWidgets">
</json-schema-form>

...or...

import { WidgetLibraryService } from 'angular2-json-schema-form';
...
constructor(private widgetLibrary: WidgetLibraryService) { }
...
// Replace existing 'input' widget:
widgetLibrary.registerWidget('input', YourInputWidgetComponent);
// Add new 'custom-control' widget:
widgetLibrary.registerWidget('custom-control', YourCustomWidgetComponent);

To see many examples of widgets, explore the source code, or call getAllWidgets() from the WidgetLibraryService to see all widgets currently available in the library. All default widget components are in the /src/lib/src/widget-library folder, and all custom Material Design widget components are in the /src/lib/src/framework-library/material-design-framework folder. (The Bootstrap 3 framework just reformats the default widgets, and so does not include any custom widgets if its own.)

Changing or adding frameworks

To change the active framework, either use the framework input of the <json-schema-form> tag, or load the FrameworkLibraryService and call setFramework(yourCustomFramework), with either the name of an available framework (by default 'material-design', 'bootstrap-3' or 'no-framework'), or with your own custom framework object in the following format:

import { YourFrameworkComponent } from './your-framework.component';
import { YourWidgetComponent } from './your-widget.component';
...
let yourCustomFramework = {
  framework: YourFrameworkComponent,                                // required
  widgets:     { 'your-widget-name': YourWidgetComponent,   ... },  // optional
  stylesheets: [ '//url-to-framework-external-style-sheet', ... ],  // optional
  scripts:     [ '//url-to-framework-external-script',      ... ]   // optional
}

...and...

<json-schema-form
  [schema]="yourJsonSchema"
  [framework]="yourCustomFramework">
</json-schema-form>

...or...

import { FrameworkLibraryService } from 'angular2-json-schema-form';
...
constructor(private frameworkLibrary: FrameworkLibraryService) { }
...
frameworkLibrary.setFramework(yourCustomFramework);

The value of the required framework key is an Angular component which will be called to format each widget before it is displayed. The optional widgets object contains any custom widgets, which will override or supplement the built-in widgets. And the optional stylesheets and scripts arrays contain URLs to any additional external style sheets or JavaScript libraries required by the framework. These are the external stylesheets and scripts that will be loaded if the "loadExternalAssets" option is set to "true".

Loading external assets required by a framework

Most Web layout framework libraries (including both Bootstrap and Material Design) need additional external JavaScript and/or CSS assets loaded in order to work properly. The best practice is to load these assets separately in your site, before calling Angular JSON Schema Form. (For the included libraries, follow these links for more information about how to do this: Bootstrap and Material Design.)

Alternately, during development, you may find it helpful to let Angular JSON Schema Form load these resources for you (as wed did in the 'Basic use' example, above), which you can do in several ways:

  • Call setFramework with a second parameter of true (e.g. setFramework('material-design', true)), or
  • Add loadExternalAssets: true to your options object, or
  • Add loadExternalAssets="true" to your <json-schema-form> tag, as shown above

Finally, if you want to see what scripts a particular framework will automatically load, after setting that framework you can call getFrameworkStylesheets() or getFrameworkScritps() from the FrameworkLibraryService to return the built-in arrays of URLs.

However, if you are creating a production site you should load these assets separately, and make sure to remove all references to loadExternalAssets to prevent the assets from being loaded twice.

Two approaches to writing your own frameworks

The two built-in frameworks (in the /src/lib/src/framework-library folder) demonstrate different strategies for how frameworks can style form elements. The Bootstrap 3 framework is very lightweight and includes no additional widgets (though it does load some external stylesheets and scripts). It works entirely by adding styles to the default widgets. In contrast, the Material Design framework uses the Material Design for Angular library to replace most of the default form control widgets with custom widgets from that library.

Contributions and future development

If you find this library useful, I'd love to hear from you. If you have any trouble with it or would like to request a feature, please post an issue on GitHub.

If you're a programmer and would like a fun intermediate-level Angular project to hack on, then clone the library and take a look at the source code. I wrote this library both because I needed an Angular JSON Schema Form builder, and also as a way to sharpen my Angular skills. This project is just complex enough to be challenging and fun, but not so difficult as to be overwhelming. One thing I particularly like is that each example in the demo playground is like a little puzzle which provides immediate feedback—as soon as it works perfectly, you know you've solved it.

I've also tried to split things into small modules as much as possible, so even though some code is still a bit messy, most individual parts should be straightforward to work with. (A lot of the code is well commented, though some isn't—but I'm working to fix that. If you run into anything you don't understand, please ask.) If you make improvements, please submit a pull request to share what you've done.

This library is mostly functional (I'm already using it in another large site, where it works well), but it still has many small bugs to fix and enhancements that could be made. Here's a random list of some stuff I know needs to be added or improved:

  • It needs a testing framework—The single biggest flaw in this library is that each change or improvement has the potential to break something else (which has already happened several times). Integrating automated tests into the build process would fix that.

  • The 'JSON Schema - Required Field' example doesn't work—Currently, required fields inside objects are always required. But when the object itself is not required, those fields should instead be dynamically required, or not, only if at least one field in the object is non-empty.

  • More frameworks—Not everyone uses Material Design or Bootstrap 3, so it would be great to create framework plug-ins for Bootstrap 4, Foundation 6, Semantic UI, or other web design frameworks.

  • More widgets—There are lots of great form controls available, such as the Pikaday calendar, Spectrum color picker, and ACE code editor, which just need small custom wrappers to convert them into Angular JSON Schema Form plug-ins.

If you like this library, need help, or want to contribute, let me know. I'm busy, so it sometimes takes me a long time to respond, but I will eventually get back to you. :-)

Thanks! I hope you enjoy using this library as much as I enjoyed writing it.

License

MIT