Custom error messages in Lua allow developers to provide clear and informative feedback when errors occur. They enhance the debugging process and improve code maintainability.

Creating Custom Error Messages

In Lua, you can create custom error messages using the error() function. This function halts the execution of the program and displays the specified error message.


function divide(a, b)
    if b == 0 then
        error("Division by zero is not allowed")
    end
    return a / b
end

print(divide(10, 0))  -- This will raise the custom error

Error Handling with Custom Messages

To handle custom errors, you can use the pcall function. It allows you to catch and process errors without crashing your program.


local success, result = pcall(function()
    return divide(10, 0)
end)

if not success then
    print("An error occurred: " .. result)
else
    print("Result: " .. result)
end

Best Practices for Custom Error Messages

Be specific and descriptive in your error messages
Include relevant information, such as function names or variable values
Use consistent formatting for all error messages in your project
Consider internationalization for multi-language support

Advanced Error Handling

For more complex error handling scenarios, you can create custom error objects. This approach allows you to include additional information with your errors.


local function createError(message, code)
    return {
        message = message,
        code = code
    }
end

function riskyOperation(value)
    if value < 0 then
        error(createError("Value must be non-negative", "INVALID_VALUE"))
    end
    -- Perform operation
end

local success, err = pcall(riskyOperation, -5)
if not success then
    print("Error code: " .. err.code)
    print("Error message: " .. err.message)
end

By using custom error messages effectively, you can significantly improve the debugging experience and overall quality of your Lua code. Remember to combine this technique with other error handling basics for robust application development.