Event Transformer Schema Creation Guide

createAbiSchema Function

The createAbiSchema function is a utility for transforming Ethereum event logs into structured, type-safe data with automatic value conversions. It helps you define how raw event data should be parsed and transformed.

Basic Structure

createAbiSchema({
  signature: string,
  fields: ({ transformer }) => Record<string, FieldTransformer>,
});

Parameters

1. signature: Ethereum event signature string that defines:

   • Event name
   • Parameter types and names
   • Event structure and format

2. fields: A function that receives a transformer object and returns field definitions

Field Transformers

Each field can use the following transformer methods:

• toToken(): Converts address to token object
• toDecimals(token): Converts value to proper decimal representation
• toPercentage(divider): Format value as percentage
• toAddress(): Formats address with checksum
• toVault(): Converts address to vault object

Example Usage

const schema = createAbiSchema({
  signature:
    "event LogUpdateExchangePrices(address token, uint256 supplyExchangePrice, uint256 borrowExchangePrice, uint256 borrowRate, uint256 utilization)",
  fields: ({ transformer }) => ({
    // Transform token address
    token: ({ value }) => {
      return transformer.transform(value).toToken();
    },
    // Transform price with token decimals
    supplyExchangePrice: ({ value, item }) => {
      return transformer
        .transform(value)
        .toDecimals(transformer.transform(item.token).toToken());
    },
    // Transform percentage values
    borrowRate: ({ value }) => {
      return transformer.transform(value).toPercentage(100);
    },
  }),
});

Field Transformer Context

Each field transformer receives an object with:

• value: The raw value from the event log
• item: Access to other fields in the event

Common Patterns

1. Token Amount Transformation:

({ value, item }) => {
  const token = transformer.transform(item.token).toToken();
  return transformer.transform(value).toDecimals(token);
};

2. Percentage Values:

({ value }) => {
  return transformer.transform(value).toPercentage(100);
};

3. Address Formatting:

({ value }) => {
  return transformer.transform(value).toAddress();
};

Testing Schemas

Test your schemas by:

1. Creating test events with known values
2. Using resolveFieldTransformer to process the event
3. Verifying the transformed output

const event = {
  address: "0x...",
  topics: [...],
  data: "0x..."
};

const resolved = resolveFieldTransformer(schema, transformer, event);
expect(resolved.token.__type).toBe("token");
expect(typeof resolved.amount).toBe("string");

Remember to test edge cases and different value formats to ensure robust transformation..