Feature/array empty (#9)

* remove data prop required

* add empty list test

Author: gusgard

src/components/GridList/__snapshots__/test.js.snap

@@ -99,6 +99,32 @@ exports[`grid list renders correctly 1`] = `
 />
 `;
 
+exports[`grid list renders empty list 1`] = `
+<FlatList
+  ItemSeparatorComponent={[Function]}
+  animationDuration={500}
+  animationInitialBackgroundColor="#FFFFFF"
+  contentContainerStyle={false}
+  data={Array []}
+  disableVirtualization={false}
+  horizontal={false}
+  initialNumToRender={10}
+  itemStyle={Object {}}
+  keyExtractor={[Function]}
+  maxToRenderPerBatch={10}
+  numColumns={3}
+  onEndReachedThreshold={2}
+  renderItem={[Function]}
+  scrollEventThrottle={50}
+  separatorBorderColor="#FFFFFF"
+  separatorBorderWidth={0}
+  showAnimation={false}
+  showsVerticalScrollIndicator={false}
+  updateCellsBatchingPeriod={50}
+  windowSize={21}
+/>
+`;
+
 exports[`grid list renders showAnimation 1`] = `
 <FlatList
   ItemSeparatorComponent={[Function]}

src/components/GridList/index.js

@@ -22,7 +22,7 @@ export default class GridList extends PureComponent {
     // Only is allowed children or data not both
     children(props, propName) {
       const { data } = props;
-      if (!props[propName] && data && data.length === 0) {
+      if (!props[propName] && !data) {
         return new Error('Invalid props, `data` or `children` is required');
       }
       if (data && data.length !== 0 && !props.renderItem) {
@@ -34,6 +34,7 @@ export default class GridList extends PureComponent {
 
   static defaultProps = {
     numColumns: 3,
+    data: [],
     itemStyle: {},
     showSeparator: false,
     showAnimation: false,

src/components/GridList/test.js

@@ -17,6 +17,16 @@ describe('grid list', () => {
     );
     expect(wrapper).toMatchSnapshot();
   });
+  
+  it('renders empty list', () => {
+    const wrapper = shallow(
+      <GridList
+        data={[]}
+        renderItem={({ item }) => <Image source={item.thumbnail} />}
+      />,
+    );
+    expect(wrapper).toMatchSnapshot();
+  });
 
   it('renders showSeparator', () => {
     const wrapper = shallow(