cleaned up exceptions and added one for estimated item size

src/RecyclerFlatList.tsx

@@ -13,12 +13,13 @@ import {
   RecyclerListView,
   RecyclerListViewProps,
 } from "recyclerlistview";
-import invariant from "invariant";
 
 import AutoLayoutView, { BlankAreaEventHandler } from "./AutoLayoutView";
 import ItemContainer from "./CellContainer";
 import WrapperComponent from "./WrapperComponent";
 import GridLayoutProviderWithProps from "./GridLayoutProviderWithProps";
+import CustomError from "./errors/CustomError";
+import ExceptionList from "./errors/ExceptionList";
 
 export interface RecyclerFlatListProps<T> extends FlatListProps<T> {
   // TODO: This is to make eslint silent. Out prettier and lint rules are conflicting.
@@ -108,25 +109,25 @@ class RecyclerFlatList<T> extends React.PureComponent<
 
   constructor(props) {
     super(props);
-    this.setup();
-  }
-
-  private setup() {
-    const refreshingPrecondition = !(
-      this.props.onRefresh && typeof this.props.refreshing !== "boolean"
-    );
-    const message =
-      'Invariant Violation: `refreshing` prop must be set as a boolean in order to use `onRefresh`, but got `"undefined"`';
-    invariant(refreshingPrecondition, message);
-    if (this.props.estimatedListSize) {
-      if (this.props.horizontal) {
-        this.listFixedDimensionSize = this.props.estimatedListSize.height;
+    this.validateProps();
+    if (props.estimatedListSize) {
+      if (props.horizontal) {
+        this.listFixedDimensionSize = props.estimatedListSize.height;
       } else {
-        this.listFixedDimensionSize = this.props.estimatedListSize.width;
+        this.listFixedDimensionSize = props.estimatedListSize.width;
       }
     }
   }
 
+  private validateProps() {
+    if (this.props.onRefresh && typeof this.props.refreshing !== "boolean") {
+      throw new CustomError(ExceptionList.refreshBooleanMissing);
+    }
+    if (!(this.props.estimatedItemSize > 0)) {
+      throw new CustomError(ExceptionList.estimatedItemSizeMissing);
+    }
+  }
+
   // Some of the state variables need to update when props change
   static getDerivedStateFromProps<T>(
     nextProps: RecyclerFlatListProps<T>,

src/errors/CustomError.ts

@@ -0,0 +1,10 @@
+export default class CustomError extends Error {
+  constructor(exception: Exception) {
+    super(`${exception.type}: ${exception.message}`);
+    this.name = exception.type;
+  }
+}
+export interface Exception {
+  type: string;
+  message: string;
+}

src/errors/ExceptionList.ts

@@ -0,0 +1,15 @@
+import { Exception } from "./CustomError";
+
+const ExceptionList: { [key: string]: Exception } = {
+  estimatedItemSizeMissing: {
+    message:
+      "`estimatedItemSize` is a required prop in RecyclerFlatList. Please provide a value that is greater than 0.",
+    type: "InvalidPropException",
+  },
+  refreshBooleanMissing: {
+    message:
+      "`refreshing` prop must be set as a boolean in order to use `onRefresh`, but got `undefined`",
+    type: "InvariantViolation",
+  },
+};
+export default ExceptionList;