typedef FormatFunction from class fcf::NTest::Logger

Type: fcf::NTest::Logger::FormatFunction

Definition: typedef std::function<void(fcf::NTest::Logger&, fcf::NTest::Logger::MessageContext&)> FormatFunction;

Available from version: 1.2.1

A function used to format a log message.

The fcf::NTest::Logger::FormatFunction is a callback type used to define custom message formatting rules. It is integrated into the fcf::NTest::Logger pipeline and is executed for every log message that matches a registered fcf::NTest::Logger::Format.

When a log event occurs, the logger iterates through all registered formats. If a format's name matches the current output target's format requirement, the FormatFunction is invoked. This function allows you to transform the raw message content, create output in a custom format, add decorative elements, or inject metadata (retrieved via the fcf::NTest::Logger::MessageContext::data property) into the final string that will be written to the output stream.

The function receives two parameters:

A reference to the fcf::NTest::Logger instance.
A reference to the fcf::NTest::Logger::MessageContext, which contains the current message, its category, level, and any attached metadata.

Note that the a_context.message property should be modified directly within the function to change the content that will eventually be sent to the output stream.

Example: Custom Message Decoration

Demonstrating how to use fcf::NTest::Logger::FormatFunction to wrap log messages in decorative brackets and convert them to uppercase.

#define FCF_TEST_IMPLEMENTATION #include <fcfTest/test.hpp> #include <iostream> #include <algorithm> #include <string> #include <regex> FCF_TEST_DECLARE("FormatDemo", "Logger", "Decorator") { // Trigger a log event fcf::NTest::log() << "hello world" << std::endl; } std::string cleanMessage(std::string a_string) { std::regex ansi_regex("\x1B\\[[0-?]*[ -/]*[@-~]"); std::string result = std::regex_replace(a_string, ansi_regex, ""); result.erase(result.find_last_not_of(" \t\n\r\f\v") + 1); return result; } int main(int a_argc, char* a_argv[]) { // Define a custom format function fcf::NTest::Logger::Format format; format.name = "decorated"; // This function will wrap the message in [MSG] and make it uppercase fcf::NTest::Logger::FormatFunction formatFunction = []( fcf::NTest::Logger&, fcf::NTest::Logger::MessageContext& context) { std::string msg = context.message; // Transform to uppercase std::transform(msg.begin(), msg.end(), msg.begin(), ::toupper); // Clear the string of terminal control commands and the last line feed msg = cleanMessage(msg); // Wrap with brackets context.message = "[<" + msg + ">]\n"; }; format.handler = formatFunction; // We use appendFormatFunc to register our custom logic fcf::NTest::logger().appendFormat(format); bool error = false; fcf::NTest::cmdRun(a_argc, a_argv, fcf::NTest::CRM_RUN, &error); return error ? 1 : 0; }

Output:

[<PERFORMING THE TEST: "FORMATDEMO" -> "LOGGER" -> "DECORATOR" ...>] [< > HELLO WORLD>] [< <term-green>[SUCCESS]</term-green> TEST COMPLETED SUCCESSFULLY (0.000`130`403 SEC)>] [<>] [<<term-green>[SUCCESS]</term-green> ALL TESTS WERE COMPLETED.>] [<TESTS: 1 PASSED, 0 FAILED, 0 SKIPPED, 1 TOTAL>] [<DURATION: 0.000`130`403 SEC>]

The application must be run by specifying the format via a command-line parameter:

app --test-format "decorated"

The fcf::NTest::Logger::FormatFunction successfully intercepted the message "hello world", transformed it to uppercase, and added the decorative brackets before it reached the output stream.