# Setting up Handlers

The handlers take data from a particular source and transform it into entities that are defined within your schema. Handlers are written in  [TypeScript](https://www.typescriptlang.org/docs/handbook/typescript-in-5-minutes.html).

For each handler that is defined in `studio.yaml` under `triggers`, create an exported function of the same name in `src/handlers` folder. 

> ```sh
> blockflow codegen
> ```

Use above command to generate boilerplate code in `path` specified in `studio.yaml`

***

### Handlers boilerplate 

Based on the trigger-type `contract/function` or `contract/event` code vary.

* Function Handler Code

```typescript
import { IFunctionContext, IBind, ISecrets } from "@blockflow-labs/utils";

/**
 * @dev Function::approve(address _spender, uint256 _value)
 * @param context trigger object with contains {functionParams: {_spender ,_value }, transaction, block}
 * @param bind init function for database wrapper methods
 */
export const approveHandler = async (
  context: IFunctionContext,
  bind: IBind,
  secrets: ISecrets,
) => {
  // Implement your function handler logic for approve here

  const { functionParams, transaction, block } = context;
  const { _spender, _value } = functionParams;
};
```

* Event Handler Code

```typescript
import {
  IEventContext,
  IBind,
  Instance,
  ISecrets,
} from "@blockflow-labs/utils";

/**
 * @dev Event::Transfer(address from, address to, uint256 value)
 * @param context trigger object with contains {event: {from ,to ,value }, transaction, block, log}
 * @param bind init function for database wrapper methods
 */
export const TransferHandler = async (
  context: IEventContext,
  bind: IBind,
  secrets: ISecrets,
) => {
  // Implement your event handler logic for Transfer here

  const { event, transaction, block, log } = context;
  const { from, to, value } = event;
};
```

To read more about handlers code use this doc.