toFunctionSelector

Returns the 4-byte function selector for a given function definition. The selector is the first 4 bytes of the keccak256 hash of the function signature.

Import

import "github.com/ChefBingbong/viem-go/utils/hash"

Usage

import "github.com/ChefBingbong/viem-go/utils/hash"

// Get function selector
selector, _ := hash.ToFunctionSelector("function ownerOf(uint256 tokenId)")
// "0x6352211e"

selector, _ = hash.ToFunctionSelector("function transfer(address to, uint256 amount)")
// "0xa9059cbb"

// Get selector as bytes
selectorBytes, _ := hash.ToFunctionSelectorBytes("function transfer(address,uint256)")
// []byte{0xa9, 0x05, 0x9c, 0xbb}

Returns

• Type: (string, error) for ToFunctionSelector, ([]byte, error) for ToFunctionSelectorBytes

The 4-byte function selector. ToFunctionSelector returns a hex string with 0x prefix, ToFunctionSelectorBytes returns raw bytes.

Parameters

function (required)

• Type: string

The function definition string. Can include the function keyword or just the signature.

// With function keyword
selector, _ := hash.ToFunctionSelector("function ownerOf(uint256 tokenId)")
// "0x6352211e"

// Without function keyword
selector, _ = hash.ToFunctionSelector("transfer(address,uint256)")
// "0xa9059cbb"

Functions

ToFunctionSelector

Returns the selector as a hex string:

selector, _ := hash.ToFunctionSelector("function transfer(address,uint256)")
// "0xa9059cbb"

ToFunctionSelectorBytes

Returns the selector as raw 4 bytes:

selectorBytes, _ := hash.ToFunctionSelectorBytes("function transfer(address,uint256)")
// []byte{0xa9, 0x05, 0x9c, 0xbb}

Notes

• The function signature is normalized (spaces removed, parameter names removed) before hashing
• Only the first 4 bytes of the keccak256 hash are used
• Function selectors are used to identify which function to call in contract interactions