Use generic Maybe

packages/instant/src/components/scaling_amount_input.tsx

@@ -2,8 +2,9 @@ import { BigNumber } from '@0x/utils';
 import * as _ from 'lodash';
 import * as React from 'react';
 
+import { Maybe } from '../types';
+
 import { ColorOption } from '../style/theme';
-import { MaybeBigNumber } from '../types';
 import { maybeBigNumberUtil } from '../util/maybe_big_number';
 import { util } from '../util/util';
 
@@ -35,7 +36,7 @@ export class ScalingAmountInput extends React.Component<ScalingAmountInputProps,
             stringValue: _.isUndefined(props.value) ? '' : props.value.toString(),
         };
     }
-    public componentDidUpdate(prevProps: ScalingAmountInputProps): void {
+    public componentDidUpdate(): void {
         const parsedStateValue = stringToMaybeBigNumber(this.state.stringValue);
         const currentValue = this.props.value;
 
@@ -73,7 +74,7 @@ export class ScalingAmountInput extends React.Component<ScalingAmountInputProps,
         });
 
         // Trigger onAmountChange with a valid BigNumber, or undefined if the sanitizedValue is invalid or empty
-        const bigNumberValue: MaybeBigNumber = _.isEmpty(sanitizedValue)
+        const bigNumberValue: Maybe<BigNumber> = _.isEmpty(sanitizedValue)
             ? undefined
             : stringToMaybeBigNumber(sanitizedValue);
 

packages/instant/src/types.ts

@@ -2,7 +2,7 @@ import { AssetProxyId, ObjectMap } from '@0x/types';
 import { BigNumber } from '@0x/utils';
 
 // Reusable
-export type MaybeBigNumber = BigNumber | undefined;
+export type Maybe<T> = T | undefined;
 export enum AsyncProcessState {
     NONE = 'None',
     PENDING = 'Pending',

packages/instant/src/util/maybe_big_number.ts

@@ -1,12 +1,12 @@
 import { BigNumber } from '@0x/utils';
 import * as _ from 'lodash';
 
-import { MaybeBigNumber } from '../types';
+import { Maybe } from '../types';
 
 export const maybeBigNumberUtil = {
-    // converts a string to a MaybeBigNumber
+    // converts a string to a Maybe<BigNumber>
     // if string is a NaN, considered undefined
-    stringToMaybeBigNumber: (stringValue: string): MaybeBigNumber => {
+    stringToMaybeBigNumber: (stringValue: string): Maybe<BigNumber> => {
         let validBigNumber: BigNumber;
         try {
             validBigNumber = new BigNumber(stringValue);
@@ -16,7 +16,7 @@ export const maybeBigNumberUtil = {
 
         return validBigNumber.isNaN() ? undefined : validBigNumber;
     },
-    areMaybeBigNumbersEqual: (val1: MaybeBigNumber, val2: MaybeBigNumber): boolean => {
+    areMaybeBigNumbersEqual: (val1: Maybe<BigNumber>, val2: Maybe<BigNumber>): boolean => {
         if (!_.isUndefined(val1) && !_.isUndefined(val2)) {
             return val1.equals(val2);
         }