Form with conditionals

This project extends react-jsonschema-form with conditional logic, which allow to have more complicated logic expressed and controlled with JSON schema. This is primarily useful for complicated schemas with extended business logic, which are suspect to changes and need to be manageable and changeable without modifying running application.

If you need simple rule logic, that does not change a lot, you can use original mozilla project, by following examples like https://jsfiddle.net/69z2wepo/68259/

The project is done to be fully compatible with mozilla, without imposing additional limitations.

Features

• Support for Json Rules Engine and json-rules-engine-simplified
• Extensible action mechanism
• Configuration over coding
• Lightweight and extensible

Installation

Install react-jsonschema-form-conditionals by running:

npm install --s react-jsonschema-form-conditionals

Usage

The simplest example of using react-jsonschema-form-conditionals

import applyRules from 'react-jsonschema-form-conditionals';
import Engine from 'json-rules-engine-simplified';
import Form from "react-jsonschema-form";

...

const rules = [{
    ...
}];

let FormWithConditionals = applyRules(schema, uiSchema, rules, Engine)(Form);

ReactDOM.render(
  <FormWithConditionals .../>,
  document.querySelector('#app')
);

To show case uses for this library we'll be using simple registration schema example

import applyRules from 'react-jsonschema-form-conditionals';
import Form from "react-jsonschema-form";

let schema = {
  definitions: {
    hobby: {
      type: "object",
      properties: {
        name: { type: "string" },
        durationInMonth: { "type": "integer" },
      }
    }
  },
  title: "A registration form",
  description: "A simple form example.",
  type: "object",
  required: [
    "firstName",
    "lastName"
  ],
  properties: {
    firstName: {
      type: "string",
      title: "First name"
    },
    lastName: {
      type: "string",
      title: "Last name"
    },
    age: {
      type: "integer",
      title: "Age",
    },
    bio: {
      type: "string",
      title: "Bio",
    },
    country: {
      type: "string",
      title: "Country"
    },
    state: {
      type: "string",
      title: "State"
    },
    zip: {
      type: "string",
      title: "ZIP"
    },
    password: {
      type: "string",
      title: "Password",
      minLength: 3
    },
    telephone: {
      type: "string",
      title: "Telephone",
      minLength: 10
    },
    hobbies: {
        type: "array",
        items: { "$ref": "#/definitions/hobby" }
    }
  }
}

let rules = [{
    ...
}]

let FormWithConditionals = applyRules(schema, uiSchema, rules, Engine)(Form);

render((
  <FormWithConditionals />
), document.getElementById("app"));

Conditionals functionality is build using 2 things

• Rules engine (Json Rules Engine or Simplified Json Rules Engine)
• Schema action mechanism

Rules engine responsibility is to trigger events, action mechanism performs needed actions on the requests.

Rules engine

Project supports 2 rules engines out of the box:

• Json Rules Engine
• Simplified Json Rules Engine

In order to use either of those, you need to specify Engine in applyRules configuration.

For example:

To use Simplified Json Rules Engine, you can do following:

import applyRules from 'react-jsonschema-form-conditionals';
import Form from "react-jsonschema-form";

import Engine from 'json-rules-engine-simplified';

...

let FormWithConditionals = applyRules(schema, uiSchema, rules, Engine)(Form);

ReactDOM.render(
  <FormWithConditionals />,
  document.querySelector('#app')
);

To use Json Rules Engine, is almost the same:

import applyRules from 'react-jsonschema-form-conditionals';
import Engine from 'json-rules-engine';
import Form from "react-jsonschema-form";

// ...

let FormWithConditionals = applyRules(schema, uiSchema, rules, Engine)(Form);

ReactDOM.render(
  <FormWithConditionals />,
  document.querySelector('#app')
);

Extending rules engine

If non of the provided engines satisfies, your needs, you can implement your own Engine which should comply to following:

class Engine {
  constructor(rules, schema) {
  }
  addRule = (rule) => {
  }
  run = (formData) => {
    return Promise[Event]
  }
}

Original rules and schema is used as a parameter for a factory call, in order to be able to have additional functionality, such as rules to schema compliance validation, like it's done in Simplified Json Rules Engine](https://github.com/RxNT/json-rules-engine-simplified)

Schema action mechanism

Rules engine emits events, which are expected to have a type and params field, type is used to distinguish action that is needed, params are used as input for that action:

{
  "type": "remove",
  "params": {
    "field": "name"
  }
}

By default action mechanism defines a supported set of rules, which you can extend as needed:

• remove removes a field or set of fields from schema and uiSchema
• require makes a field or set of fields required

Remove action

If you want to remove a field, your configuration should look like this:

    {
      "conditions": { },
      "event": {
        "type": "remove",
        "params": {
          "field": "password"
        }
      }
    }

When condition is met, password will be removed from both schema and uiSchema.

In case you want to remove multiple fields name, password, rule should look like this:

    {
      "conditions": { },
      "event": {
        "type": "remove",
        "params": {
          "field": [ "name", "password" ]
        }
      }
    }

To remove nested schema properties, use json dot notation. e.g. For schema object:

  {
    "type": "object",
    "properties": {
      "someParentWrapper": {
        "type": "object",
        "properties": {
          "booleanValA": {
            "type": "boolean",
            "title": "Some boolean input"
          },
          "booleanValB": {
            "type": "boolean",
            "title": "Another boolean input"
          }
        }
      }
    }
  }

You can remove the nested booleanValA or booleanValB like so:

  {
    "conditions": { },
    "event": {
      "type": "remove",
      "params": {
        "field": "someParentWrapper.booleanValA"
      }
    }
  }

Require action

The same convention goes for require action

For a single field:

    {
      "conditions": { },
      "event": {
        "type": "require",
        "params": {
          "field": "password"
        }
      }
    }

For multiple fields:

    {
      "conditions": { },
      "event": {
        "type": "require",
        "params": {
          "field": [ "name", "password"]
        }
      }
    }

UiSchema actions

API defines a set of actions, that you can take on uiSchema, they cover most of the

• uiAppend appends uiSchema specified in params with an original uiSchema
• uiOverride replaces field in original uiSchema with fields in params, keeping unrelated entries
• uiRepalce replaces whole uiSchema with a conf schema

To show case, let's take a simple schema

{
  "properties": {
    "lastName": { "type": "string" },
    "firstName": { "type": "string" },
    "nickName": { "type": "string"}
  }
}

and uiSchema

{
  "ui:order": ["firstName"],
  "lastName": {
    "classNames": "col-md-1",
  },
  "firstName": {
    "ui:disabled": false,
    "num": 23
  },
  "nickName": {
    "classNames": "col-md-12"
  }
}

with event params something like this

{
  "ui:order": [ "lastName" ],
  "lastName": {
    "classNames": "has-error"
  },
  "firstName" : {
    "classNames": "col-md-6",
    "ui:disabled": true,
    "num": 22
  }
}

And look at different results depend on the choosen action.

uiAppend

UiAppend can handle arrays and string, with fallback to uiOverride behavior for all other fields.

So the expected result uiSchema will be:

{
  "ui:order": ["firstName", "lastName"],
  "lastName": {
    "classNames": "col-md-1 has-error"
  },
  "firstName": {
    "classNames": "col-md-6",
    "ui:disabled": true,
    "num": 22
  },
  "nickName": {
    "classNames": "col-md-12"
  }
}

In this case it

• added lastName to ui:order array,
• appended has-error to classNames in lastName field
• added classNames and enabled firstName
• as for the num in firstName it just overrode it

This is useful for example if you want to add some additional markup in your code, without touching layout that you've defined.

uiOverride

uiOverride behaves similar to append, but instead of appending it completely replaces overlapping values

So the expected result uiSchema will be:

{
  "ui:order": [ "lastName" ],
  "lastName": {
    "classNames": "has-error"
  },
  "firstName": {
    "classNames": "col-md-6",
    "ui:disabled": true,
    "num": 22
  },
  "nickName": {
    "classNames": "col-md-12"
  }
}

In this case it

• ui:order was replaced with configured value
• className for the lastName was replaced with has-error
• added classNames and enabled firstName
• as for the num in firstName it just overrode it

uiReplace

uiReplace just replaces all fields in uiSchema with params fields, leaving unrelated fields untouched.

So the result uiSchema will be

{
  "ui:order": [ "lastName" ],
  "lastName": {
    "classNames": "has-error"
  },
  "firstName" : {
    "classNames": "col-md-6",
    "ui:disabled": true,
    "num": 22
  },
  "nickName": {
     "classNames": "col-md-12"
   }
}

Extension mechanism

You can extend existing actions list, by specifying extraActions on the form.

Let's say we need to introduce replaceClassNames action, that would just specify classNames col-md-4 for all fields except for ignored one. We also want to trigger it only when password is empty.

This is how we can do this:

import applyRules from 'react-jsonschema-form-conditionals';
import Engine from 'json-rules-engine-simplified';
import Form from "react-jsonschema-form";

...

const rules = [
    {
        conditons: {
            password: "empty"
        },
        event: {
            type: "replaceClassNames",
            params: {
                classNames: "col-md-4",
                ignore: [ "password" ]
            }
        }
    }
];


let extraActions = {
    replaceClassNames: function(params, schema, uiSchema, formData) {
        Object.keys(schema.properties).forEach((field) => {
            if (uiSchema[field] === undefined) {
                uiSchema[field] = {}
            }
            uiSchema[field].classNames = params.classNames;
        }
    }
};

let FormWithConditionals = applyRules(schema, uiSchema, rules, Engine, extraActions)(Form);

ReactDOM.render(
  <FormWithConditionals/>,
  document.querySelector('#app')
);

Provided snippet does just that.

Extension with calculated values

In case you need to calculate value, based on other field values, you can also do that.

Let's say we want to have schema with a, b and sum fields

import applyRules from 'react-jsonschema-form-conditionals';
import Engine from 'json-rules-engine-simplified';
import Form from "react-jsonschema-form";

...

const rules = [
    {
        conditons: {
            a: { not: "empty" },
            b: { not: "empty" }
        },
        event: {
            type: "updateSum"
        }
    }
];


let extraActions = {
    updateSum: function(params, schema, uiSchema, formData) {
        formData.sum = formData.a + formData.b;
    }
};

let FormWithConditionals = applyRules(schema, uiSchema, rules, Engine, extraActions)(Form);

ReactDOM.render(
  <FormWithConditionals/>,
  document.querySelector('#app')
);

This is how you can do that.

WARNING!!! You need to be careful with a rules order, when using calculated values. Put calculation rules at the top of your rules specification.

For example, let's say you want to mark sum field, if you have sum greater than 10. The rule would look something like this:

{
  "conditions": {
    "sum": { "greater" : 10 }
  },
  "event": {
    "type": "appendClass",
    "classNames": "has-success"
  }
}

But it will work only if you put it after updateSum rule, like this

[
    {
        "conditons": {
            "a": { "not": "empty" },
            "b": { "not": "empty" }
        },
        "event": {
            "type": "updateSum"
        }
    },
    {
      "conditions": {
        "sum": { "greater" : 10 }
      },
      "event": {
        "type": "appendClass",
        "classNames": "has-success"
      }
    }
];

Otherwise it will work with old sum values and therefor show incorrect value.

Rules order

Originally actions performed in sequence defined in the array. If you have interdependent rules, that you need to run in order you can specify order on a rule, so that it would be executed first. Rules are executed based on order from lowest to highest with rules without order executed last.

For example to make updateSum work regardless the order rules were added, you can do following:

[
    {
      "conditions": {
        "sum": { "greater" : 10 }
      },
      "order": 1,
      "event": {
        "type": "appendClass",
        "classNames": "has-success"
      }
    },
    {
        "conditons": {
            "a": { "not": "empty" },
            "b": { "not": "empty" }
        },
        "order": 0,
        "event": {
            "type": "updateSum"
        }
    }
]

Here although updateSum comes after appendClass, it will be executed first, since it has a lower order.

Action validation mechanism

All default actions are validated by default, checking that field exists in the schema, to save you some headaches. There are 2 levels of validation

• propTypes validation, using FB prop-types package
• explicit validation

You can define those validations in your actions as well, to improve actions usability.

All validation is disabled in production.

Prop types action validation

This is reuse of familiar prop-types validation used with React components, and it's used in the same way:

In case of require it can look like this:

require.propTypes = {
  field: PropTypes.oneOfType([
    PropTypes.string,
    PropTypes.arrayOf(PropTypes.string),
  ]).isRequired,
};

The rest is magic.

WARNING, the default behavior of prop-types is to send errors to console, which you need to have running in order to see them.

For our replaceClassNames action, it can look like this:

replaceClassNames.propTypes = {
  classNames: PropTypes.string.isRequired,
  ignore: PropTypes.arrayOf(PropTypes.string)
};

Explicit validation

In order to provide more granular validation, you can specify validate function on your action, that will receive params, schema and uiSchema so you could provide appropriate validation.

For example, validation for require can be done like this:

  require.validate = function({ field }, schema, uiSchema) {
    if (Array.isArray(field)) {
      field
        .filter(f => schema && schema.properties && schema.properties[f] === undefined)
        .forEach(f => console.error(`Field  "${f}" is missing from schema on "require"`));
    } else if (
      schema &&
      schema.properties &&
      schema.properties[field] === undefined
    ) {
      console.error(`Field  "${field}" is missing from schema on "require"`);
    }
  };

Validation is not mandatory, and will be done only if field is provided.

For our replaceClassNames action, it would look similar:

  replaceClassNames.validate = function({ ignore }, schema, uiSchema) {
    if (Array.isArray(field)) {
      ignore
        .filter(f => schema && schema.properties && schema.properties[f] === undefined)
        .forEach(f => console.error(`Field  "${f}" is missing from schema on "replaceClassNames"`));
    } else if (
      schema &&
      schema.properties &&
      schema.properties[ignore] === undefined
    ) {
      console.error(`Field  "${ignore}" is missing from schema on "replaceClassNames"`);
    }
  };

Listening to configuration changes

In order to listen for configuration changes you can specify onSchemaConfChange, which will be notified every time schema or uiSchema changes it's value.

let FormWithConditionals = applyRules(schema, uiSchema, rules, Engine, extraActions)(Form);

ReactDOM.render(
  <FormWithConditionals onSchemaConfChange = {({ schema, uiSchema }) => { console.log("configuration changed") }}/>,
  document.querySelector('#app')
);

Contribute

• Issue Tracker: github.com/RxNT/react-jsonschema-form-conditionals/issues
• Source Code: github.com/RxNT/react-jsonschema-form-conditionals

Support

If you are having issues, please let us know.

License

The project is licensed under the Apache-2.0 license.

Migration

Migration to 0.4.x

The only significant change is signature of applyRules call. In 0.4.0 schema, uiSchema, rules, Engine and extraActions all consider to be constant that is why, they moved to applyRules call. This helps improve performance on large schemas.