Logging

Dioxus has a wide range of supported platforms, each with their own logging requirements. We'll discuss the different options available to you.

The Log Crate

The Log crate is the most universally recognized logging facade in Rust. It is also the easiest to work with in Dioxus; therefore we will be focusing on loggers that work with this crate.

The log crate provides a variety of simple println-like macros with varying levels of severity.

fn main() {
    log::trace!("trace");
    log::debug!("debug");
    log::info!("info");
    log::warn!("warn");
    log::error!("error");
}

All the loggers provided on this page are, besides configuration and initialization, interfaced using these macros. Often you will also utilize the log crate's LevelFilter enum. This enum usually represents the lowest log severity you want your application to emit and can be loaded from a configuration file, environment variable, or other.

For more information, visit log crate's docs.

Dioxus Logger

Dioxus Logger is a planned-to-be feature-rich logger that supports all of Dioxus' platforms. Currently only Desktop, Web, and any server-based targets work with Dioxus Logger.

The easiest way to use Dioxus Logger is by calling the init() function:

use log::LevelFilter;

fn main() {
    // Init logger
    dioxus_logger::init(LevelFilter::Info).expect("failed to init logger");
    // Dioxus code
}

The dioxus_logger::init() function initializes Dioxus Logger with the log crate using the default configuration and provided LevelFilter.

Custom Format

Dioxus Logger allows you more control with the ability to set a custom format using the new function on the DioxusLogger struct:

use log::LevelFilter;

fn main() {
    // Init logger
    dioxus_logger::DioxusLogger::new(LevelFilter::Info)
        .use_format("[{LEVEL}] {PATH} - {ARGS}")
        .build()
        .expect("failed to init logger");

    // Dioxus code
}

In this example, we are building a new DioxusLogger struct, providing the LevelFilter, calling the use_format() function, and initializing the logger with the build() function (acts as init() in the previous example).

The key function call in this example is use_format(). This function takes a &str that specifies how you want your logs to be formatted. To specify a variable in the format, you wrap it's name in {}.

The available variables are:

• LEVEL - The LevelFilter of the emitted log.
• PATH - The file path of where the log was emitted, or the crate name.
• ARGS - The arguments passed through the log macro.
• TIMESTAMP - A timestamp of when the log was emitted. (Requires timestamps feature)

Timestamps

Another feature of Dioxus Logger is the ability to include timestamps with your logs. By default, this feature is disabled and has to be enabled by adding timestamps to your features section of the dioxus-logger dependency:

dioxus-logger = { version = "*", features = ["timestamps"] }

By enabling this feature, you gain access to the TIMESTAMP format variable.

Platform Intricacies

On web, Dioxus Logger will use web-sys to interact with console.log() to output your logs to the browser's console. On Desktop and server-based targets, Dioxus Logger will output using println().

Final Notes

Dioxus Logger is the preferred logger to use with Dioxus if it suites your needs. There are many more features to come and Dioxus Logger is planned to become an integral part of Dioxus. If there are any feature suggestions or issues with Dioxus Logger, feel free to reach out on the Dioxus Discord Server!

For more information, visit Dioxus Logger's docs.

Desktop and Server

For Dioxus' desktop and server targets, you can generally use the logger of your choice.

Some popular options are:

• env_logger
• simple_logger
• pretty_env_logger

To keep this guide short, we will not be covering the usage of these loggers.

For a full list of popular log-based logging crates, visit this list in the log crate's docs.

Web

WASM Logger is a logging interface that can be used with Dioxus' web platform.

The easiest way to use WASM Logger is with the init function:

fn main() {
    // Init logger
    wasm_logger::init(wasm_logger::Config::default());

    // Dioxus code
}

This starts WASM Logger with a LevelFilter of Debug.

To specify a custom LevelFilter, build the Config struct:

use log::LevelFilter;

fn main() {
    // Init logger
    let log_config = wasm_logger::Config::new(LevelFilter::Info);
    wasm_logger::init(log_config);

    // Dioxus code
}

Platform Intricacies

WASM Logger also uses the web-sys crate to output to the console.

For more information, visit wasm-logger's docs.

Android

Android Logger is a logging interface that can be used when targeting Android. Android Logger runs whenever an event native_activity_create is called by the Android system:

use log::LevelFilter;
use android_logger::Config;

fn native_activity_create() {
    android_logger::init_once(
        Config::default()
            .with_max_level(LevelFilter::Info)
            .with_tag("myapp");
    );
}

The with_tag() is what your app's logs will show as.

Viewing Logs

Android logs are sent to logcat. To use logcat through the Android debugger, run:

adb -d logcat

Your Android device will need developer options/usb debugging enabled.

For more information, visit android_logger's docs.

iOS

The current option for iOS is the oslog crate.

fn main() {
    // Init logger
    OsLogger::new("com.example.test")
        .level_filter(LevelFilter::Debug)
        .init()
        .expect("failed to init logger");
    // Dioxus code
}

Viewing Logs

You can view the emitted logs in Xcode.

For more information, visit oslog.