From 50fb56362ccdfbf8840bd7207081444cf7e9920c Mon Sep 17 00:00:00 2001
From: Yvonnick FRIN <frin.yvonnick@gmail.com>
Date: Mon, 6 Jan 2020 15:38:20 +0100
Subject: [PATCH] :sparkles: Expose internal methods using ref (#38)

---
 README.md          |  59 ++++++++++++++++++
 example/src/App.js |  23 ++++++-
 src/index.js       | 152 +++++++++++++++++++++++++++------------------
 3 files changed, 174 insertions(+), 60 deletions(-)

diff --git a/README.md b/README.md
index f8e300f..9385148 100644
--- a/README.md
+++ b/README.md
@@ -62,6 +62,65 @@ function Example({ items, fetchMore, hasMore }) {
 | loadMoreItems | no       | function | A function that will be called each time the list need to load more items.                                                                                                                                |
 | placeholder   | no       | node     | Any render-able value like strings or React.Nodes to be displayed while `children` is loading                                                                                                             |
 | customScrollbar   | no       | boolean     | A boolean that determines if [react-custom-scrollbars](https://github.com/malte-wessel/react-custom-scrollbars) is used instead of native one                                                      |
+| ref   | no       | ref or function     | A ref or a callback ref to get component instance so you can call instance's methods (see [Methods section](/README.md#methods))                                                     |
+
+## Methods
+
+**scrollTo(scrollOffset: number): void**
+
+see [FixedSizeList](https://react-window.now.sh/#/api/FixedSizeList) methods section.
+
+**scrollToItem(index: number, align: string = "auto"): void**
+
+see [FixedSizeList](https://react-window.now.sh/#/api/FixedSizeList) methods section.
+
+**resetloadMoreItemsCache(): void**
+
+Clear previously loaded items from cache.
+
+example
+```jsx
+import React from 'react'
+
+import InfiniteLoading from 'react-simple-infinite-loading'
+
+function Example({ items, fetchMore, hasMore }) {
+  const ref = React.useRef()
+  const scrollToTop = () => {
+    if (ref.current) {
+      ref.current.scrollTo(0)
+    }
+  }
+  const scrollTo50 = () => {
+    if (ref.current) {
+      ref.current.scrollToItem(50)
+    }
+  }
+  const resetCache = () => {
+    if (ref.current) {
+      ref.current.resetloadMoreItemsCache()
+    }
+  }
+
+  return (
+    <>
+      <button onClick={scrollToTop}>Scroll to top</button>
+      <button onClick={scrollTo50}>Scroll to 50</button>
+      <button onClick={resetCache}>Reset cache</button>
+      <div style={{ width: 300, height: 300 }}>
+        <InfiniteLoading
+          hasMoreItems={hasMore}
+          itemHeight={40}
+          loadMoreItems={fetchMore}
+          ref={ref}
+        >
+          {items.map(item => <div key={item}>{item}</div>)}
+        </InfiniteLoading>
+      </div>
+    </>
+  )
+}
+```
 
 ## License
 
diff --git a/example/src/App.js b/example/src/App.js
index 1250ca5..2524824 100644
--- a/example/src/App.js
+++ b/example/src/App.js
@@ -1,8 +1,24 @@
-import React, { useState } from 'react'
+import React, { useState, useRef } from 'react'
 import InfiniteLoading from 'react-simple-infinite-loading'
 
 export default function App() {
   const [items, setItems] = useState([...Array(100)].map((_, index) => index))
+  const ref = useRef()
+  const scrollToTop = () => {
+    if (ref.current) {
+      ref.current.scrollTo(0)
+    }
+  }
+  const scrollTo50 = () => {
+    if (ref.current) {
+      ref.current.scrollToItem(50)
+    }
+  }
+  const resetCache = () => {
+    if (ref.current) {
+      ref.current.resetloadMoreItemsCache()
+    }
+  }
 
   const loadMoreItems = () => {
     const newItems = [...Array(100)].map((_, index) => items.length + index)
@@ -19,11 +35,16 @@ export default function App() {
     <div className="app">
       <h1>React simple infinite loading example</h1>
 
+      <button onClick={scrollToTop}>Scroll to top</button>
+      <button onClick={scrollTo50}>Scroll to 50</button>
+      <button onClick={resetCache}>Reset cache</button>
       <h2>Start scrolling here :</h2>
       <InfiniteLoading
         hasMoreItems
         itemHeight={40}
         loadMoreItems={loadMoreItems}
+        customScrollbar
+        ref={ref}
       >
         {items.map(item => <div className="item" key={item}>{item}</div>)}
       </InfiniteLoading>
diff --git a/src/index.js b/src/index.js
index 56041b3..c683439 100644
--- a/src/index.js
+++ b/src/index.js
@@ -1,4 +1,4 @@
-import React, { forwardRef } from 'react'
+import React, { Component, createRef } from 'react'
 import PropTypes from 'prop-types'
 
 import { FixedSizeList as List } from 'react-window'
@@ -10,60 +10,104 @@ const CustomScrollbarsVirtualList = React.forwardRef((props, ref) => (
   <CustomScrollbars {...props} forwardedRef={ref} />
 ))
 
-const InfiniteLoading = forwardRef((
-  {
-    children,
-    hasMoreItems,
-    itemsCount,
-    itemHeight,
-    loadMoreItems,
-    placeholder,
-    customScrollbar
-  },
-  ref
-) => {
-  let effectiveCount = itemsCount
-  if (effectiveCount === undefined) {
-    effectiveCount = hasMoreItems ? children.length + 1 : children.length
+class InfiniteLoading extends Component {
+  static propTypes = {
+    hasMoreItems: PropTypes.bool,
+    loadMoreItems: PropTypes.func,
+    itemsCount: PropTypes.number,
+    children: PropTypes.array.isRequired,
+    itemHeight: PropTypes.number.isRequired,
+    placeholder: PropTypes.node,
+    customScrollbar: PropTypes.bool
   }
 
-  const isItemLoaded = index => !hasMoreItems || index < children.length
+  constructor(props) {
+    super(props)
+    this.infiniteLoaderRef = createRef()
+    this.fixedSizeListRef = null
+  }
 
-  return (
-    <AutoSizer>
-      {({ height, width }) => (
-        <InfiniteLoader
-          isItemLoaded={isItemLoaded}
-          itemCount={effectiveCount}
-          loadMoreItems={loadMoreItems}
-          ref={ref}
-        >
-          {({ onItemsRendered, ref }) => (
-            <List
-              height={height}
-              itemCount={effectiveCount}
-              itemSize={itemHeight}
-              onItemsRendered={onItemsRendered}
-              ref={ref}
-              width={width}
-              outerElementType={customScrollbar ? CustomScrollbarsVirtualList : null}
-            >
-              {({ index, style }) => (
-                <div style={style}>
-                  {children[index] != null ? children[index] : placeholder}
-                </div>
-              )}
-            </List>
-          )}
-        </InfiniteLoader>
-      )}
-    </AutoSizer>
-  )
-})
+  resetloadMoreItemsCache() {
+    if (this.infiniteLoaderRef.current) {
+      this.infiniteLoaderRef.current.resetloadMoreItemsCache()
+    } else {
+      throw Error('The InfiniteLoader component is not mounted yet')
+    }
+  }
+
+  scrollTo(...args) {
+    if (this.fixedSizeListRef) {
+      this.fixedSizeListRef.scrollTo(...args)
+    } else {
+      throw Error('The FixedSizeList component is not mounted yet')
+    }
+  }
+
+  scrollToItem(...args) {
+    if (this.fixedSizeListRef) {
+      this.fixedSizeListRef.scrollToItem(...args)
+    } else {
+      throw Error('The FixedSizeList component is not mounted yet')
+    }
+  }
+
+  render() {
+    const {
+      children,
+      hasMoreItems,
+      itemsCount,
+      itemHeight,
+      loadMoreItems,
+      placeholder,
+      customScrollbar
+    } = this.props
+
+    let effectiveCount = itemsCount
+    if (effectiveCount === undefined) {
+      effectiveCount = hasMoreItems ? children.length + 1 : children.length
+    }
+
+    const isItemLoaded = index => !hasMoreItems || index < children.length
+
+    return (
+      <AutoSizer>
+        {({ height, width }) => (
+          <InfiniteLoader
+            isItemLoaded={isItemLoaded}
+            itemCount={effectiveCount}
+            loadMoreItems={loadMoreItems}
+            ref={this.infiniteLoaderRef}
+          >
+            {({ onItemsRendered, ref: setListRef }) => (
+              <List
+                height={height}
+                itemCount={effectiveCount}
+                itemSize={itemHeight}
+                onItemsRendered={onItemsRendered}
+                ref={listRef => {
+                  this.fixedSizeListRef = listRef
+                  setListRef(listRef)
+                }}
+                width={width}
+                outerElementType={customScrollbar ? CustomScrollbarsVirtualList : null}
+              >
+                {({ index, style }) => (
+                  <div style={style}>
+                    {children[index] != null ? children[index] : placeholder}
+                  </div>
+                )}
+              </List>
+            )}
+          </InfiniteLoader>
+        )}
+      </AutoSizer>
+    )
+  }
+}
 
 CustomScrollbars.propTypes = {
   onScroll: PropTypes.func.isRequired,
-  forwardedRef: PropTypes.node.isRequired,
+  forwardedRef: PropTypes.func.isRequired,
   style: PropTypes.object.isRequired,
   children: PropTypes.node.isRequired
 }
@@ -88,14 +132,4 @@ function CustomScrollbars ({ onScroll, forwardedRef, style, children }) {
   )
 }
 
-InfiniteLoading.propTypes = {
-  hasMoreItems: PropTypes.bool,
-  loadMoreItems: PropTypes.func,
-  itemsCount: PropTypes.number,
-  children: PropTypes.array.isRequired,
-  itemHeight: PropTypes.number.isRequired,
-  placeholder: PropTypes.node,
-  customScrollbar: PropTypes.bool
-}
-
 export default InfiniteLoading