react-hook-form-jsonschema

react-hook-form-jsonschema

Small project based on react-hook-form that exposes an API for easily creating customizable forms based on a JSON Schema with built-in validation.

react-hook-form-jsonschema is a React hooks library that manages all the stateful logic needed to make a form, based on a JSON Schema, functional. It returns a set of props that are meant to be called and their results destructured on the input field desired.

Table of Contents

• react-hook-form-jsonschema
  • Simple Usage
  • Installation
  • Components API
    • FormContext component
  • Hooks API
    • useHidden(path)
    • useInput(path)
    • useObject(path, UISchema)
    • usePassword(path)
    • useRadio(path)
    • useSelect(path)
    • useTextArea(path)

Simple Usage

Suppose you have a simple JSON Schema that stores a person's first name:

const personSchema = {
  $id: 'https://example.com/person.schema.json',
  $schema: 'http://json-schema.org/draft-07/schema#',
  title: 'Person',
  type: 'object',
  properties: {
    firstName: {
      type: 'string',
      description: "The person's first name.",
    },
  },
}

And suppose you want to create a form field for the firstName field, simply use the useInput() hook for this and then render the form using react

function FirstNameField(props) {
  const inputMethods = useInput('#/firstName');

  return (
    <FormContext schema={personSchema}>
      <label {...inputMethods.getLabelProps()}>
        {inputMethods.name}
      </label>
      <input {...inputMethods.getInputProps()} />
    </FormContext>
  )
}

Installation

With npm:

npm install react-hook-form-jsonschema --save

Or with yarn:

yarn add react-hook-form-jsonschema

Components API

FormContext component API

This component is the top-level component that creates the context with the schema and options all the hooks will need to be usable. So bear in mind that you need to define all the other components as children of this.

props:

Required:

• schema: JSON Schema object which will be passed down by context for the inputs to use it for validation and the structure of the form itself.

Optional:

• mode: String to indicate when to validate the input, default is 'onSubmit'.
  • 'onBlur': Validate when an input field is blurred
  • 'onChange': Validate when an input field value changes
  • 'onSubmit': Validate when the submit is triggered
• revalidateMode: String to indicate when inputs with errors get re-validated, default is 'onChange'.
  • 'onblur': Validate when an input field is blurred
  • 'onChange': Validate when an input field value changes
  • 'onSubmit': Validate when the submit is triggered
• submitFocusError: Boolean, when true focus on the first field with error after submit validates, if there is any. Defaults to true.
• onSubmit: Callback function that the form values are passed to when submit is triggered
• noNativeValidate: Boolean, when true disables the default browser validation (notice that react-hook-form-jsonschema does NOT yet implement validation form URIs and email addresses).

Hooks API

The following are the common fields returned in the object from every use'SomeInputType' hook:

• type: The type of the input, as defined in InputTypes:
  • generic: the default type, a non specialized type, only contains the common fields
  • radio: Type used for <input type='radio' \>
  • select: Type used for <select>
  • input: Type used for generic <input \>
  • textArea: Type used for <textarea>
• path: Path in the jsonschema this input is validated against. The path is always in the form: #/some/child/data/field/here where # represents the root of the schema, and the some/child/data/field/here represents the tree of objects (from some to here) to get to the desired field, which in this case is here.
• name: The last object/data field name in the tree. In the case of #/some/child/data/field/here the name value will be here.
• isRequired: indicates wether the field is required or not.
• formContext: If you want to access internal react-hook-form context use this
• getError(): Returns an ErrorMessage, which has the following format:
  • {message: ErrorTypes, expected: ErrorMessageValues}
  • ErrorTypes, is an enum, with the following values:
    • required: the field is required to be filled
    • maxLength: maximum lenght of string input was surpassed
    • minLength: minimum lenght of string input was not met
    • maxValue: maximum value of number input was surpassed
    • minValue: minimum value of number input was not met
    • pattern: the pattern or type defined in the schema was not met
    • multipleOf: the number is not a multiple of the number defined in the schema
    • undefinedError: the error type could not be defined
  • ErrorMessageValues, is the expected value to be met, it will be true for required, and the minimum value expected for minValue for example.
• getObject(): Returns the data field in the schema that this input refers to

Please notice that in all of the examples bellow it is assumed that the components are already children of a FormContext component

useHidden(path)

Description

Use this hook to build a hidden field in the form, the user will not be able to change it or see it, but it will be there when submitted.

Parameters:

• path: String which represents the path to the data field of the JSON Schema that this input will be built for.

Return:

Returns an object with the following fields, besides the common one's:

• getLabelProps(): use this with the spread operator inside a <label> tag and get the benefit of having all the important fields of the label filled in for you and the associated input (the for property) with it.
• getInputProps(): use this with the spread operator inside an <input> tag and get the benefit of the validator, id field, name and an associated label with it

Example:

function HiddenField(props) {
  const inputMethods = useHidden('#/some/child/you/want/hidden');

  return (
    <React.Fragment>
      <label {...inputMethods.getLabelProps()}>
        {inputMethods.name}
      </label>
      <input {...inputMethods.getInputProps()} />
    </React.Fragment>
  )
}

useInput(path)

Description

Use this hook to build a generic input field in your form, with validation based on the type of input the JSON Schema requires.

Parameters:

• path: String which represents the path to the data field of the JSON Schema that this input will be built for.

Return:

Returns an object with the following fields, besides the common one's:

• getLabelProps(): use this with the spread operator inside a <label> tag and get the benefit of having all the important fields of the label filled in for you and the associated input (the for property) with it.
• getInputProps(): use this with the spread operator inside an <input> tag and get the benefit of the validator, id field, name and an associated label with it.

Example:

function InputField(props) {
  const inputMethods = useInput('#/some/child/you/want/as/input');

  return (
    <React.Fragment>
      <label {...inputMethods.getLabelProps()}>
        {inputMethods.name}
      </label>
      <input {...inputMethods.getInputProps()} />
    </React.Fragment>
  )
}

useObject(path, UISchema)

Description

This hook works a little differently than the others. This hook will return an array of which each of its elements corresponds to the return type of one of the other hooks.

Parameters:

• path: String which represents the path to the data field of the JSON Schema that this input will be built for.
• UISchema (Optional): This UISchema is a modified schema type, relative to the object passed in the path prop, the format of the UISchema is the following:

const UISchema = {
  /* This is the type that will be used to choose what type of input will be
   *  used to build the specified field. Please note that the type of a node
   *  that is an object will be ignored, as there would make no sense to render
   *  an object without it's children inside a form.
   */
  type: UITypes,
  properties: {
    // Note that the definition is recursive
    child1NameHere: UISchema,
    child2NameHere: UISchema,
    // ...
    childXNameHere: UISchema,
  },
}

• The UITypes is an enum with the following values:
  • default: input will have a default type based on what react-hook-form-jsonschema thinks is better.
  • radio: input will be of the radio type, just as returned by the useRadio hook
  • select: input will be of the select type, just as returned by the useSelect hook
  • input: input will be of the input type, just as returned by the useInput hook
  • hidden: input will be of the hidden type, just as returned by the useHidden hook
  • password: input will be of the password type, just as returned by the usePassword hook
  • textArea: input will be of the textarea type, just as returned by the useTextArea hook

Return:

Returns an array, with each element being the return of a different call to a hook for each child of the object that was passed in the path

Example:

const personSchema = {
  title: 'Person',
  type: 'object',
  properties: {
    firstName: {
      type: 'string',
      description: "The person's first name.",
    },
    lastName: {
      type: 'string',
      description: "The person's last name.",
    },
    birthYear: {
      description: "The person's birth year.",
      type: 'integer',
      minimum: 1930,
      maximum: 2010,
    },
  },
}

function SpecializedObject(props) {
  switch (props.baseObject.type) {
    case InputTypes.input: {
      return (
        <React.Fragment>
          <label {...props.baseObject.getLabelProps()}>
            {props.baseObject.name}
          </label>
          <input {...props.baseObject.getInputProps()} />
        </React.Fragment>
      )
    }
    case InputTypes.radio: {
      return (
        <React.Fragment>
          <label {...props.baseObject.getLabelProps()}>
            {props.baseObject.name}
          </label>
          {props.baseObject.getItems().map((value, index) => {
            return (
              <label
                {...props.baseObject.getItemLabelProps(index)}
                key={`${value}${index}`}
              >
                {value}
                <input {...props.baseObject.getItemInputProps(index)} />
              </label>
            )
          })}
        </React.Fragment>
      )
    }
    case InputTypes.select: {
      return (
        <React.Fragment>
          <label {...props.baseObject.getLabelProps()}>
            {props.baseObject.name}
          </label>
          <select {...props.baseObject.getSelectProps()}>
            {props.baseObject.getItems().map((value, index) => {
              return (
                <option
                  {...props.baseObject.getItemOptionProps(index)}
                  key={`${value}${index}`}
                >
                  {value}
                </option>
              )
            })}
          </select>
        </React.Fragment>
      )
    }
  }
  return <React.Fragment></React.Fragment>
}

function ObjectRenderer(props) {
  const inputMethods = useObject({ path: props.path, UISchema: props.UISchema })

  const objectForm = []

  // Note that we also add error checking here and show a message in case there
  // is one. Remember that you can also check for the type of error returned
  // anb give a more specialized warning to the user.
  for (const obj of inputMethods) {
    objectForm.push(
      <div key={`${obj.type}${obj.path}`}>
        <SpecializedObject baseObject={obj} />
        {obj.getError() && <p>This is an error!</p>}
      </div>
    )
  }

  return <React.Fragment>{objectForm}</React.Fragment>
}

function RenderMyJSONSchema() {
  // Notice that even though only one child was specified, all the children of
  // the root object are rendered, using the choosen default for each field.
  const UISchema = {
    type: UITypes.default,
    properties: {
      birthYear: {
        type: UITypes.select,
      },
    },
  }

  return (
    <FormContext schema={personSchema}>
      <ObjectRenderer path="#" UISchema={UISchema} />
    </FormContext>
  )
}

This is the result of this example:

usePassword(path)

Description

Use this hook to build a password input field in your form, with validation based on the type of input the JSON Schema requires.

Parameters:

• path: String which represents the path to the data field of the JSON Schema that this input will be built for.

Return:

Returns an object with the following fields, besides the common one's:

• getLabelProps(): use this with the spread operator inside a <label> tag and get the benefit of having all the important fields of the label filled in for you and the associated input (the for property) with it.
• getInputProps(): use this with the spread operator inside an <input> tag and get the benefit of the validator, id field, name and an associated label with it

Example:

function PasswordField(props) {
  const inputMethods = usePassword('#/some/child/you/want/as/input');

  return (
    <React.Fragment>
      <label {...inputMethods.getLabelProps()}>
        {inputMethods.name}
      </label>
      <input {...inputMethods.getInputProps()} />
    </React.Fragment>
  )
}

useRadio(path)

Description

Use this hook to build a radio field in your form.

Parameters:

• path: String which represents the path to the data field of the JSON Schema that this input will be built for.

Return:

Returns an object with the following fields, besides the common one's:

• getItems(): use this to get which values should be listed inside the radio input fields. This function derives the items by the defined type and properties inside the JSON Schema and returns all the required items to comply with the definition.
• getItemInputProps(index): use this with the spread operator inside an <input> tag and get the benefit of the validator, id field, name and an associated label with it for the item in the specified index from getItems()
• getItemLabelProps(index): the label props related to the input at the specified index from getItems()

Example:

function InputField(props) {
  const inputMethods = useRadio('#/some/child/with/limited/possible/values');

  return (
    <React.Fragment>
      {inputMethods.getItems().map((value, index) => {
        return (
          <label {...inputMethods.getItemLabelProps(index)} key={`${value}${index}`}>
            {value}
            <input {...inputMethods.getItemInputProps(index)} />
          </label>
        )
      })}
      {inputMethods.getError() && <p>This is an error!</p>}
    </React.Fragment>
  )
}

useSelect(path)

Description

Use this hook to build a select field in your form.

Parameters:

• path: String which represents the path to the data field of the JSON Schema that this input will be built for.

Return:

Returns an object with the following fields, besides the common one's:

• getLabelProps(): use this with the spread operator inside a <label> tag and get the benefit of having all the important fields of the label filled in for you and the associated select (the for property) with it.
• getItems(): use this to get all the values that are possible to be in the radio buttons
• getItemOptionProps(index): use this with the spread operator inside an <option> tag and get the benefit of the validator, id field and name for the item in the specified index from getItems()
• getSelectProps(): use this with the spread operator inside a <select> tag to get validation and register it with the react-hook-form-jsonschema.

Example:

function InputField(props) {
  const inputMethods = useSelect('#/some/child/with/limited/possible/values');

  return (
    <React.Fragment>
      <label {...inputMethods.getLabelProps()}>{inputMethods.name}</label>
      <select {...inputMethods.getSelectProps()}>
        {inputMethods.getItems().map((value, index) => {
          return (
            <option
              {...inputMethods.getItemOptionProps(index)}
              key={`${value}${index}`}
            >
              {value}
            </option>
          )
        })}
      </select>
      {inputMethods.getError() && <p>This is an error!</p>}
    </React.Fragment>
  )
}

useTextArea(path)

Description

Use this hook to build a textarea field in the form.

Parameters:

• path: String which represents the path to the data field of the JSON Schema that this input will be built for.

Return:

Returns an object with the following fields, besides the common one's:

• getLabelProps(): use this with the spread operator inside a <label> tag and get the benefit of having all the important fields of the label filled in for you and the associated input (the for property) with it.
• getTextAreaProps(): use this with the spread operator inside an <textarea> tag and get the benefit of the validator, id field, name and an associated label with it

Example:

function HiddenField(props) {
  const inputMethods = useTextArea('#/some/child/you/want/as/TextArea');

  return (
    <React.Fragment>
      <label {...inputMethods.getLabelProps()}>
        {inputMethods.name}
      </label>
      <textarea {...inputMethods.getTextAreaProps()} />
    </React.Fragment>
  )
}