logging-guide

name	logging-guide
description	OSLog logging conventions — Logger setup, log levels, category naming, and migration from print().

Logging Guide

Overview

All logging in the codebase uses Apple's OSLog framework via Logger. Never use print() for logging.

Reference Implementation

See VultisigApp/VultisigApp/Core/Networking/HTTPClient.swift for the canonical example.

Setup

import OSLog

// In a class:
class MyService {
    private let logger = Logger(subsystem: "com.vultisig.app", category: "my-service")
}

// In a struct or View (file-level, above the type):
private let logger = Logger(subsystem: "com.vultisig.app", category: "my-view")

struct MyView: View { ... }

Convention

Item	Rule
Subsystem	Always "com.vultisig.app"
Category	Kebab-case, describes the component (e.g., "http-client", "tx-history-recorder", "home-screen")
Access	private let logger — never expose loggers publicly

Log Levels

Level	Usage	Example
logger.debug()	Verbose info for development	logger.debug("Headers: \(headers)")
logger.info()	Normal operational events	logger.info("Cleaned up \(count) old transactions")
logger.warning()	Recoverable issues	logger.warning("Request cancelled")
logger.error()	Failures that need attention	logger.error("Failed to load: \(error)")

Migrating from print()

1. Add import OSLog (alphabetical order with other imports)
2. Add the logger property (class) or file-level constant (struct/View)
3. Replace print("ClassName: message \(value)") with the appropriate log level
4. Drop the class name prefix from the message — OSLog's category handles identification
5. Choose the right level: errors → .error(), info/status → .info(), debug data → .debug()

Anti-patterns

// BAD: print()
print("MyService: Failed to save: \(error)")

// BAD: Redundant class name in message
logger.error("MyService: Failed to save: \(error)")

// GOOD
logger.error("Failed to save: \(error)")