unwrap-err-panic

Function Signature

(unwrap-err-panic response-input)

• Input: (response A B)
• Output: B

Why it matters

The unwrap-err-panic function is crucial for:

1. Unpacking error responses to access their inner values.
2. Implementing logic that requires handling error responses.
3. Ensuring data integrity by validating the error unpacking process.
4. Simplifying the process of handling error responses in smart contracts by throwing runtime errors when necessary.

When to use it

Use unwrap-err-panic when you need to:

• Unpack error responses to access their inner values.
• Implement logic that requires handling error responses.
• Validate the error unpacking process to ensure data integrity.
• Handle error responses in your smart contract and throw runtime errors when necessary.

Best Practices

• Ensure the input value is a response type.
• Use meaningful variable names for better readability.
• Combine with other error handling functions for comprehensive error management.
• Handle the possible error cases to ensure robust contract behavior.

Practical Example: Unpacking an Error Response and Throwing a Runtime Error

Let's implement a function that processes an error response using unwrap-err-panic:

(define-public (process-error-response (input (response int int)))
  (let ((error-value (unwrap-err-panic input)))
    (ok error-value)
  )
)

;; Usage
(process-error-response (err 42)) ;; Returns (ok 42)
(process-error-response (ok 1)) ;; Throws a runtime exception

This example demonstrates:

1. Using unwrap-err-panic to unpack an error response.
2. Implementing a public function to handle the error unpacking process.
3. Handling both successful and error cases, with runtime errors thrown for ok values.

Common Pitfalls

1. Using unwrap-err-panic with values that are not response types, causing runtime errors.
2. Assuming the error unpacking will always succeed, leading to unhandled error cases.
3. Not handling all possible conditions, resulting in incomplete error management.
4. Overlooking the need for proper error handling and validation.

Related Functions

• unwrap!: Unpacks optional and response types, returning a thrown value if unpacking fails.
• unwrap-err!: Unpacks error responses, returning a thrown value if the response is ok.
• try!: Unpacks optional and response types, returning none or the err value if unpacking fails.

Conclusion

The unwrap-err-panic function is a fundamental tool for unpacking error responses and throwing runtime errors in Clarity smart contracts. It allows developers to implement logic that requires handling error responses, ensuring data integrity and simplifying the error unpacking process. When used effectively, unwrap-err-panic enhances the reliability and maintainability of your smart contract code by providing a clear and concise way to handle error responses and throw runtime errors when necessary.