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This guide covers advanced patterns for creating sophisticated custom components that handle complex scenarios, including composite components, context access, performance optimization, and cross-component communication.

​
Composite Components (Components with Children)

Composite components can contain other components, enabling complex layouts and reusable patterns. Use the node annotation to describe a component property that may contain child components. By default, the children property is considered a property that contains child components.

​
Example: Card Container


const Card = ({
                title,
                children,
                bordered,
                shadow,
                size,
                bodyStyle
              }: any) => {
  return (
    <div className={`card card--${size} ${bordered ? 'card--bordered' : ''} ${shadow ? 'card--shadow' : ''}`}>
      {title && (
        <div className="card__header">
          {title}
        </div>
      )}
      <div className="card__body" style={bodyStyle}>
        {children}
      </div>
    </div>
  )
}

export const card = define(Card, 'Card')
  .props({
    children: node, // ← Enables child components!
    title: node, // ← Enables child components!
    bordered: boolean.default(true),
    shadow: boolean.default(false),
    size: oneOf('small', 'medium', 'large').default('medium'),
    bodyStyle: object,
  })
  .build()
Usage in JSON: 
{
  "key": "userCard",
  "type": "Card",
  "props": {
    "shadow": {
      "value": true
    }
  },
  "children": [
    {
      "key": "Header",
      "type": "MuiTypography",
      "slot": "title",
      "props": {
        "variant": {
          "value": "h4"
        },
        "children": {
          "value": "User Information"
        }
      }
    },
    {
      "key": "userName",
      "type": "MuiTextField",
      "props": {
        "label": {
          "value": "Full Name"
        }
      }
    },
    {
      "key": "userEmail",
      "type": "MuiTextField",
      "props": {
        "label": {
          "value": "Email Address"
        }
      }
    }
  ]
}

​
Live Example

live
function App() {
  const Card = ({
                  title,
                  children,
                  bordered,
                  shadow,
                  size,
                  bodyStyle
                }) => {
    return (
      <div className={`card card--${size} ${bordered ? 'card--bordered' : ''} ${shadow ? 'card--shadow' : ''}`}>
        {title && (
          <div className="card__header">
            {title}
          </div>
        )}
        <div className="card__body" style={bodyStyle}>
          {children}
        </div>
      </div>
    )
  }

  const card = define(Card, 'Card')
    .props({
      children: node,
      title: node,
      bordered: boolean.default(true),
      shadow: boolean.default(false),
      size: oneOf('small', 'medium', 'large').default('medium'),
      bodyStyle: object,
    })
    .build()

  const view = muiView
  view.define(card.model)

  const formJson = {
    "form": {
      "key": "Screen",
      "type": "Screen",
      "children": [
        {
          "key": "userCard",
          "type": "Card",
          "props": {
            "shadow": {
              "value": true
            }
          },
          "children": [
            {
              "key": "Header",
              "type": "MuiTypography",
              "slot": "title",
              "props": {
                "variant": {
                  "value": "h4"
                },
                "children": {
                  "value": "User Information"
                }
              }
            },
            {
              "key": "userName",
              "type": "MuiTextField",
              "props": {
                "label": {
                  "value": "Full Name"
                }
              }
            },
            {
              "key": "userEmail",
              "type": "MuiTextField",
              "props": {
                "label": {
                  "value": "Email Address"
                }
              }
            }
          ]
        }
      ]
    }
  }

  return (
    <FormViewer
      view={view}
      getForm={() => JSON.stringify(formJson)}
    />
  )
}

​
Accessing Form Context

Components can access the form data and other context. The useComponentData hook returns component data, which is used by FormEngine Core to render the component. You can get the form data, component value, and other data using this hook. 

const ContextAwareComponent = ({value, onChange}: any) => {
  // Get component-specific data
  const componentData = useComponentData()
  const field = componentData.field
  const currentValue = '' + (field?.value ?? '')

  // Get all form data
  const formData = componentData.root.data

  // Check validation state
  const hasErrors = componentData.root.hasErrors

  return (
    <div className="context-aware">
      <input
        value={value}
        onChange={e => onChange(e.target.value)}
        disabled={hasErrors}
      />
      <p>Value: {currentValue}</p>
      <p>Form data ({hasErrors ? 'invalid' : 'valid'}):</p>
      <pre>
        {JSON.stringify(formData, null, 2)}
      </pre>
    </div>
  )
}

export const contextAwareComponent = define(ContextAwareComponent, 'ContextAwareComponent')
  .props({
    value: string.valued.uncontrolledValue('')
  })
  .build()

​
Live Example

live
function App() {
  const ContextAwareComponent = ({value, onChange}) => {
    // Get component-specific data
    const componentData = useComponentData()
    const field = componentData.field
    const currentValue = '' + (field?.value ?? '')

    // Get all form data
    const formData = componentData.root.data

    // Check validation state
    const hasErrors = componentData.root.hasErrors

    return (
      <div className="context-aware">
        <input
          value={value}
          onChange={e => onChange(e.target.value)}
          disabled={hasErrors}
        />
        <p>Value: {currentValue}</p>
        <p>Form data ({hasErrors ? 'invalid' : 'valid'}):</p>
        <pre>
        {JSON.stringify(formData, null, 2)}
      </pre>
      </div>
    )
  }

  const contextAwareComponent = define(ContextAwareComponent, 'ContextAwareComponent')
    .props({
      value: string.valued.uncontrolledValue('')
    })
    .build()

  const view = muiView
  view.define(contextAwareComponent.model)

  const formJson = {
    "errorType": "MuiErrorWrapper",
    "form": {
      "key": "Screen",
      "type": "Screen",
      "children": [
        {
          "key": "contextAwareComponent",
          "type": "ContextAwareComponent"
        },
        {
          "key": "Header",
          "type": "MuiTypography",
          "slot": "title",
          "props": {
            "variant": {
              "value": "h4"
            },
            "children": {
              "value": "User Information"
            }
          }
        },
        {
          "key": "userName",
          "type": "MuiTextField",
          "props": {
            "label": {
              "value": "Full Name"
            }
          }
        },
        {
          "key": "userEmail",
          "type": "MuiTextField",
          "props": {
            "label": {
              "value": "Email Address"
            }
          },
          "schema": {
            "type": "string",
            "validations": [
              {
                "key": "email"
              },
              {
                "key": "required"
              }
            ]
          }
        }
      ]
    }
  }

  return (
    <FormViewer
      view={view}
      getForm={() => JSON.stringify(formJson)}
    />
  )
}

​
Summary

Advanced component patterns enable you to:
  • Create reusable, composite components
  • Access and manipulate form context
Key takeaways:
  • Use .node for container components
  • Access component data with useComponentData()
Next Steps: Happy advanced component building! 🚀
Last modified on April 16, 2026