diff --git a/cli.js b/cli.js
index 7998d11..d6609d5 100644
--- a/cli.js
+++ b/cli.js
@@ -51,6 +51,7 @@ let wait = time => new Promise(resolve => setTimeout(resolve, time))
     --as            target platform
                       react-dom (default)
                       react-native
+                      react-pdf
     --clean         clean the autogenerated .view.js files
     --local         default local language, defaults to English (en)
     --tools         use with Views Tools, defauls to true when
diff --git a/ensure-data.js b/ensure-data.js
index 451d2d5..28badb2 100644
--- a/ensure-data.js
+++ b/ensure-data.js
@@ -5,98 +5,130 @@ let USE_DATA = `// This file is automatically generated by Views and will be ove
 // when the morpher runs. If you want to contribute to how it's generated, eg,
 // improving the algorithms inside, etc, see this:
 // https://github.com/viewstools/morph/blob/master/ensure-data.js
-import get from 'lodash/get'
-import produce from 'immer'
-import set from 'lodash/set'
-import React, { useContext, useEffect, useMemo, useReducer } from 'react'
-import parseDate from 'date-fns/parse'
-import parseISO from 'date-fns/parseISO'
-import formatDate from 'date-fns/format'
-import isValidDate from 'date-fns/isValid'
-
-let identity = { in: i => i, out: i => i }
+import * as fromValidate from './Data/validators.js';
+import get from 'lodash/get';
+import produce from 'immer';
+import set from 'lodash/set';
+import React, { useContext, useEffect, useMemo, useReducer, useRef } from 'react';
+import parseDate from 'date-fns/parse';
+import parseISO from 'date-fns/parseISO';
+import formatDate from 'date-fns/format';
+import isValidDate from 'date-fns/isValid';
+
+let identity = { in: i => i, out: i => i };
 
 // show
-let ItemContext = React.createContext({})
-export let ItemProvider = ItemContext.Provider
-export let useItem = (path = null, format = identity) => {
-  let item = useContext(ItemContext)
-
-  return useMemo(() => (
-    path? format.in(get(item, path)) : item
-  ), [item, path, format]) // eslint-ignore-line
+let ItemContext = React.createContext({});
+export let ItemProvider = ItemContext.Provider;
+export let useItem = ({ path = null, format = identity } = {}) => {
+  let item = useContext(ItemContext);
+
+  return useMemo(() => (path ? { value: format.in(get(item, path)) } : item), [
+    item,
+    path,
+    format,
+  ]); // eslint-ignore-line
   // ignore get
-}
+};
 
 // capture
 let captureItemReducer = produce((draft, action) => {
   switch (action.type) {
     case CAPTURE_SET_FIELD: {
-      set(draft, action.key, action.value)
-      break
+      set(draft, action.key, action.value);
+      break;
     }
 
     case CAPTURE_RESET: {
-      return action.state
+      return action.state;
     }
 
     default: {
       throw new Error(
         \`Unknown action type "\${action.type}" in update item reducer.\`
-      )
+      );
     }
   }
-})
-let CAPTURE_SET_FIELD = 'capture/SET_FIELD'
+});
+let CAPTURE_SET_FIELD = 'capture/SET_FIELD';
 export let setField = (key, value) => ({
   type: CAPTURE_SET_FIELD,
   key,
   value,
-})
-let CAPTURE_RESET = 'capture/RESET'
-export let reset = state => ({ type: CAPTURE_RESET, state })
-
-let CaptureItemContext = React.createContext({})
-export let CaptureItemProvider = CaptureItemContext.Provider
-export let useCaptureItem = (path = null, format = identity) => {
-  let captureItem = useContext(CaptureItemContext)
+});
+let CAPTURE_RESET = 'capture/RESET';
+export let reset = state => ({ type: CAPTURE_RESET, state });
+
+let CaptureItemContext = React.createContext({});
+export let CaptureItemProvider = CaptureItemContext.Provider;
+export let useCaptureItem = ({
+  path = null, format = identity, validate = null
+} = {}) => {
+  let captureItem = useContext(CaptureItemContext);
+  let touched = useRef(false);
+
+  if (process.env.NODE_ENV === 'development') {
+    if (validate && !(validate in fromValidate)) {
+      throw new Error(
+        \`"\${validate}" function doesn't exist or is not exported in Data/validators.js\`
+      );
+    }
+  }
 
   return useMemo(() => {
-    if (!path) return captureItem
+    if (!path) return captureItem;
 
     let [item, dispatch, onSubmit] = captureItem;
 
+    if (!item) return {};
+
+    let value = format.in(get(item, path));
+    let isValid =
+      touched.current && validate ? fromValidate[validate](value) : true;
+    let onChange = value => {
+      touched.current = true;
+      dispatch(setField(path, format.out(value)));
+    }
     return {
-      onChange: value => dispatch(setField(path, format.out(value))),
+      onChange,
       onSubmit,
-      value: format.in(get(item, path)),
-    }
-  }, [captureItem, path, format])
-}
+      value,
+      isValid,
+      isInvalid: !isValid
+    };
+  }, [captureItem, path, format, validate]);
+};
 export let useCaptureItemProvider = (item, onSubmit) => {
-  let [state, dispatch] = useReducer(captureItemReducer, item)
+  let [state, dispatch] = useReducer(captureItemReducer, item);
 
   useEffect(() => {
-    dispatch(reset(item))
-  }, [item])
+    dispatch(reset(item));
+  }, [item]);
 
-  return useMemo(() => [state, dispatch, onSubmit], [state, dispatch, onSubmit])
-}
+  return useMemo(() => [state, dispatch, onSubmit], [
+    state,
+    dispatch,
+    onSubmit,
+  ]);
+};
 
 function formatDateInOut(rvalue, formatIn, formatOut, whenInvalid = '') {
   let value =
     formatIn === 'iso'
       ? parseISO(rvalue)
-      : parseDate(rvalue, formatIn, new Date())
-  return isValidDate(value) ? formatDate(value, formatOut) : whenInvalid
+      : parseDate(rvalue, formatIn, new Date());
+  return isValidDate(value) ? formatDate(value, formatOut) : whenInvalid;
 }
 
 export let useMakeFormatDate = (formatIn, formatOut, whenInvalid) =>
-  useMemo(() => ({
-    in: value => formatDateInOut(value, formatIn, formatOut, whenInvalid),
-    out: value => formatDateInOut(value, formatOut, formatIn, whenInvalid),
-  }), []) // eslint-disable-line
-  // ignore formatIn, formatouOut, whenInvalid
+  useMemo(
+    () => ({
+      in: value => formatDateInOut(value, formatIn, formatOut, whenInvalid),
+      out: value => formatDateInOut(value, formatOut, formatIn, whenInvalid),
+    }),
+    []
+  ); // eslint-disable-line
+// ignore formatIn, formatouOut, whenInvalid
 `
 
 export default function ensureIsBefore({ src }) {
diff --git a/ensure-flow.js b/ensure-flow.js
index ec8d33a..ef32f53 100644
--- a/ensure-flow.js
+++ b/ensure-flow.js
@@ -8,7 +8,7 @@ function ensureFirstStoryIsOn(flow, key, stories) {
   if (!stories.has(key)) return
 
   let story = flow.get(key)
-  if (story.stories.size > 0) {
+  if (story && story.stories.size > 0) {
     let index = 0
     for (let id of story.stories) {
       if (index === 0 || !story.isSeparate) {
diff --git a/fonts.js b/fonts.js
index 920be0e..6f78a71 100644
--- a/fonts.js
+++ b/fonts.js
@@ -9,6 +9,7 @@ import relativise from './relativise.js'
 let morphFont = {
   'react-dom': morphFontAsReactDom,
   'react-native': morphFontAsReactNative,
+  'react-pdf': morphFontAsReactNative,
 }
 
 export async function ensureFontsDirectory(src) {
diff --git a/morph/react-dom.js b/morph/react-dom.js
index aef9e27..1925105 100644
--- a/morph/react-dom.js
+++ b/morph/react-dom.js
@@ -44,6 +44,7 @@ export default ({
     cssStatic: false,
     data: view.parsed.view.data,
     dataFormat: view.parsed.view.dataFormat,
+    dataValidate: view.parsed.view.dataValidate,
     dependencies: new Set(),
     flow: null,
     setFlow: false,
diff --git a/morph/react-dom/get-value-for-property.js b/morph/react-dom/get-value-for-property.js
index 7bc7ebb..ff209e2 100644
--- a/morph/react-dom/get-value-for-property.js
+++ b/morph/react-dom/get-value-for-property.js
@@ -60,10 +60,12 @@ export default (node, parent, state) => {
     state.data &&
     (node.value === 'props.value' ||
       node.value === 'props.onSubmit' ||
-      node.value === 'props.onChange')
+      node.value === 'props.onChange' ||
+      node.value === 'props.isInvalid' ||
+      node.value === 'props.isValid')
   ) {
     return {
-      [node.name]: `{${node.value.replace('props.', '')} || ${node.value}}`,
+      [node.name]: `{${node.value.replace('props.', 'data.')}}`,
     }
   } else if (isValidImgSrc(node, parent)) {
     return {
diff --git a/morph/react-native.js b/morph/react-native.js
index fa4a4f3..34b824d 100644
--- a/morph/react-native.js
+++ b/morph/react-native.js
@@ -23,6 +23,7 @@ export default ({
   getSystemImport,
   local,
   localSupported,
+  reactNativeLibraryImport = 'react-native',
   track,
   view,
   viewsById,
@@ -44,6 +45,7 @@ export default ({
     images: [],
     data: view.parsed.view.data,
     dataFormat: view.parsed.view.dataFormat,
+    dataValidate: view.parsed.view.dataValidate,
     dependencies: new Set(),
     flow: null,
     setFlow: false,
@@ -74,6 +76,7 @@ export default ({
     testIdKey: 'testID',
     testIds: {},
     track,
+    reactNativeLibraryImport,
     usedBlockNames: { [finalName]: 1, AutoSizer: 1, Column: 1, Table: 1 },
     uses: [],
     use(block, isLazy = false) {
diff --git a/morph/react-native/get-value-for-property.js b/morph/react-native/get-value-for-property.js
index c192ecf..2d42852 100644
--- a/morph/react-native/get-value-for-property.js
+++ b/morph/react-native/get-value-for-property.js
@@ -56,7 +56,18 @@ let getImageSource = (node, state, parent) => {
 }
 
 export default (node, parent, state) => {
-  if (isValidImgSrc(node, parent)) {
+  if (
+    state.data &&
+    (node.value === 'props.value' ||
+      node.value === 'props.onSubmit' ||
+      node.value === 'props.onChange' ||
+      node.value === 'props.isValid' ||
+      node.value === 'props.isInvalid')
+  ) {
+    return {
+      [node.name]: `{${node.value.replace('props.', 'data.')}}`,
+    }
+  } else if (isValidImgSrc(node, parent)) {
     return (
       !parent.isSvg && {
         source: getImageSource(node, state, parent),
diff --git a/morph/react-pdf.js b/morph/react-pdf.js
new file mode 100644
index 0000000..e258c8f
--- /dev/null
+++ b/morph/react-pdf.js
@@ -0,0 +1,7 @@
+import reactNativeMorph from './react-native.js'
+
+export default options =>
+  reactNativeMorph({
+    ...options,
+    reactNativeLibraryImport: '@react-pdf/renderer',
+  })
diff --git a/morph/react/block-off-when.js b/morph/react/block-off-when.js
index f1b3a05..3b6fc89 100644
--- a/morph/react/block-off-when.js
+++ b/morph/react/block-off-when.js
@@ -10,8 +10,13 @@ export function enter(node, parent, state) {
     node.onWhen = true
 
     if (parent && !isList(parent)) state.render.push('{')
-
-    state.render.push(`${onWhen.value} ? `)
+    let value = onWhen.value
+    if (state.data && value === 'props.isInvalid') {
+      value = 'data.isInvalid'
+    } else if (state.data && value === 'props.isValid') {
+      value = 'data.isValid'
+    }
+    state.render.push(`${value} ? `)
   } else if (isStory(node, state)) {
     node.onWhen = true
     state.render.push(`{flow.has("${state.pathToStory}/${node.name}") ? `)
diff --git a/morph/react/get-body.js b/morph/react/get-body.js
index a4010d7..32e5e20 100644
--- a/morph/react/get-body.js
+++ b/morph/react/get-body.js
@@ -75,18 +75,19 @@ export default ({ state, name }) => {
   if (state.data) {
     switch (state.data.type) {
       case 'show': {
-        data.push(`let value = fromData.useItem('${state.data.path}'`)
+        data.push(`let data = fromData.useItem({ path: '${state.data.path}', `)
         maybeDataFormat(state.dataFormat, data)
-        data.push(')')
+        data.push('})')
         break
       }
 
       case 'capture': {
         data.push(
-          `let { value, onChange, onSubmit }= fromData.useCaptureItem('${state.data.path}'`
+          `let data = fromData.useCaptureItem({ path: '${state.data.path}', `
         )
         maybeDataFormat(state.dataFormat, data)
-        data.push(')')
+        maybeDataValidate(state.dataValidate, data)
+        data.push('})')
         break
       }
 
@@ -126,10 +127,14 @@ function maybeDataFormat(format, data) {
   if (format.type !== 'date') return
 
   data.push(
-    `, fromData.useMakeFormatDate('${format.formatIn}', '${format.formatOut}'`
+    `format: fromData.useMakeFormatDate('${format.formatIn}', '${format.formatOut}'`
   )
   if (format.whenInvalid) {
     data.push(`, '${format.whenInvalid}'`)
   }
-  data.push(`)`)
+  data.push(`),`)
+}
+function maybeDataValidate(validate, data) {
+  if (!validate || validate.type !== 'js') return
+  data.push(`validate: '${validate.value}',`)
 }
diff --git a/morph/react/get-dependencies.js b/morph/react/get-dependencies.js
index 8f464d6..1e6ef99 100644
--- a/morph/react/get-dependencies.js
+++ b/morph/react/get-dependencies.js
@@ -126,7 +126,11 @@ export default (state, getImport) => {
   }
 
   if (usesNative.length > 0) {
-    dependencies.push(`import { ${usesNative.join(', ')} } from 'react-native'`)
+    dependencies.push(
+      `import { ${usesNative.join(', ')} } from '${
+        state.reactNativeLibraryImport
+      }'`
+    )
   }
 
   if (state.track) {
diff --git a/morph/react/property-text.js b/morph/react/property-text.js
index 9c4cd75..ee5c2db 100644
--- a/morph/react/property-text.js
+++ b/morph/react/property-text.js
@@ -26,7 +26,9 @@ let parseFormatValue = (value, type) => {
 
 export function enter(node, parent, state) {
   if (node.name === 'text' && parent.name === 'Text') {
-    if (hasCustomScopes(node, parent)) {
+    if (state.data && node.value === 'props.value') {
+      parent.explicitChildren = '{data.value}'
+    } else if (hasCustomScopes(node, parent)) {
       parent.explicitChildren = wrap(getScopedCondition(node, parent))
     } else if (isSlot(node)) {
       parent.explicitChildren = wrap(node.value)
diff --git a/morphers.js b/morphers.js
index 4e1b4a4..b72186c 100644
--- a/morphers.js
+++ b/morphers.js
@@ -1,7 +1,9 @@
 import reactDom from './morph/react-dom.js'
 import reactNative from './morph/react-native.js'
+import reactPdf from './morph/react-pdf.js'
 
 export default {
   'react-dom': reactDom,
   'react-native': reactNative,
+  'react-pdf': reactPdf,
 }
diff --git a/package.json b/package.json
index 88c18db..6ff8ffc 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@viewstools/morph",
-  "version": "19.7.2",
+  "version": "19.9.0",
   "description": "Views language morpher",
   "main": "index.js",
   "type": "module",
diff --git a/parse/helpers.js b/parse/helpers.js
index 8068d34..dfc69f3 100644
--- a/parse/helpers.js
+++ b/parse/helpers.js
@@ -261,6 +261,14 @@ export let getDataFormat = maybeProp => {
   }
 }
 
+export let getDataValidate = maybeProp => {
+  if (!maybeProp || !maybeProp.value) return null
+  return {
+    type: 'js',
+    value: maybeProp.value,
+  }
+}
+
 export let getFormat = line => {
   let properties = {}
   let values = line.split(' ')
diff --git a/parse/index.js b/parse/index.js
index 38af66e..44b9b16 100644
--- a/parse/index.js
+++ b/parse/index.js
@@ -7,6 +7,7 @@ import {
   getComment,
   getData,
   getDataFormat,
+  getDataValidate,
   getFormat,
   getProp,
   getPropType,
@@ -806,6 +807,9 @@ That would mean that SomeView in ${block.name} will be replaced by ${block.name}
     view.dataFormat = getDataFormat(
       view.properties.find(p => p.name === 'dataFormat')
     )
+    view.dataValidate = getDataValidate(
+      view.properties.find(p => p.name === 'dataValidate')
+    )
   } else {
     view.isStory = false
   }