swift-log

name	swift-log
description	A lightweight, level-based Swift logging utility with emoji indicators, Unicode decoding for network payloads, configurable log levels, and optional file logging with LRU expiration. Use when adding logs, debugging network requests, configuring log output levels, or writing logs to files in Swift/iOS projects.
license	MIT
compatibility	Requires Swift 4.0+, iOS 9.0+, Xcode 9.0+
metadata	{"author":"zjinhu","version":"1.0","github":"https://github.com/zjinhu/SwiftLog"}

SwiftLog - Level-Based Swift Logging

When to Use

• Adding log statements to Swift code
• Debugging network requests with Unicode payload support
• Configuring log output levels (trace/debug/net/info/warning/error/fault)
• Writing logs to files with automatic expiration
• Replacing print() statements with structured logging

Quick Start

Import

import SwiftLog
// or if using CocoaPods:
import Swift_Log

Configuration (App Delegate / Entry Point)

// Set minimum log level (logs below this are ignored)
SLog.defaultLogDegree = .debug

// Toggle network logs independently
SLog.showNetLog = false

// Set max log file age in seconds (default: 7 days)
// Must be set BEFORE enabling addFileLog
SLog.maxLogAge = 60 * 60 * 24 * 7

// Enable file logging
SLog.addFileLog = true

// Get log file URL for upload/sharing
let logURL = SLog.getLogFileURL

Log Levels (Lowest → Highest)

Level	Function	Emoji	Use Case
trace	SLogTrace()	⚪	Ignorable details, verbose tracing
debug	SLogDebug()	✅	Development/debugging info
net	SLogNet()	🌐	Network requests/responses (toggleable)
info	SLogInfo()	🔔	Important information
warning	SLogWarning()	⚠️	Potential issues
error	SLogError()	❌	Errors that occurred
fault	SLogFault()	‼️	Critical/fatal errors

Global Functions (Recommended)

SLogTrace("User tapped button, current state: \(state)")
SLogDebug("Parsing JSON response: \(jsonString)")
SLogNet("POST /api/users | Body: {\"name\":\"John\"} | \\u8bf7\\u6c42\\u6210\\u529f")
SLogInfo("User logged in successfully: \(userId)")
SLogWarning("Disk space running low: \(availableSpace)MB")
SLogError("Failed to fetch data: \(error.localizedDescription)")
SLogFault("Database corruption detected in table: \(tableName)")

Class Methods (Alternative)

SLog.trace("Trace message")
SLog.debug("Debug message")
SLog.net("Network message")
SLog.info("Info message")
SLog.warning("Warning message")
SLog.error("Error message")
SLog.fault("Fault message")

LogDegree Enum

public enum LogDegree: Int {
    case trace = 0   // Track program execution
    case debug = 1   // Debugging information
    case net = 2     // Network requests/responses
    case info = 3    // Important information
    case warning = 4 // Warning messages
    case error = 5   // Error messages
    case fault = 6   // Critical/fatal errors
}

Key Features

Unicode Decoding

Network logs automatically decode Unicode escape sequences:

SLogNet("\\u6253\\u5370\\u6d88\\u606f")
// Output: 打印消息

File Logging

• Logs written to Caches directory (SLog.txt)
• Automatic LRU expiration (default: 7 days)
• Access via SLog.getLogFileURL

DEBUG-Only Output

Logs only print to console in DEBUG builds. Release builds skip console output but can still write to files.

Auto-Captured Context

Every log automatically captures:

• Source file name
• Function name
• Line number

Output Format

🌐 Network 🌐 | 2021-03-05 15:27:33:609 
 所在类:ViewController.swift 
 方法名:viewDidLoad() 
 所在行:31 
<<<<<<<<<<<<<<<<信息>>>>>>>>>>>>>>>>

 POST /api/users | Body: {"name":"John"}

<<<<<<<<<<<<<<<<END>>>>>>>>>>>>>>>>

Common Patterns

Error Handling

do {
    let data = try fetchData()
    SLogInfo("Fetched \(data.count) records")
} catch {
    SLogError("Fetch failed: \(error.localizedDescription)")
    SLogFault("Critical: Data fetch failed at \(#function)")
}

Network Requests

SLogNet("Request: \(request.httpMethod ?? "GET") \(url)")
SLogNet("Response: \(response.statusCode) | Body: \\(responseBody)")

State Transitions

SLogTrace("State transition: \(oldState) -> \(newState)")
SLogDebug("ViewModel updated with \(items.count) items")

Warnings & Errors

guard let user = currentUser else {
    SLogWarning("No current user found, using guest session")
    return
}

SLogError("Failed to save user: \(error)")

Best Practices

1. Use appropriate levels: Don't use .error for informational messages
2. Network logs: Use SLogNet() for all API traffic; toggle with showNetLog
3. File logging: Enable in production for crash reporting; set maxLogAge appropriately
4. Unicode: Network logs auto-decode \uXXXX sequences - no manual conversion needed
5. Performance: @autoclosure ensures message is only evaluated if log level passes