# apexSubstring (/docs/core/reference/api/functions/apexSubstring)



[@kysoql/core](/docs/core/reference/api) / apexSubstring

```ts
function apexSubstring(
   source,
   beginIndex,
   endIndex
): ApexBindExpression<string>;
```

Builds a typed Apex substring expression using validated zero-based
indexes.

## Parameters [#parameters]

| Parameter    | Type                                                                                                     |
| ------------ | -------------------------------------------------------------------------------------------------------- |
| `source`     | \| `string` \| [`ApexBindExpression`](/docs/core/reference/api/interfaces/ApexBindExpression)\<`string`> |
| `beginIndex` | `number`                                                                                                 |
| `endIndex`   | `number`                                                                                                 |

## Returns [#returns]

[`ApexBindExpression`](/docs/core/reference/api/interfaces/ApexBindExpression)\<`string`>