AppLogger

Logging system, providing useful debug information for each print log.

Pros

• easy to use across the app

• easy type filtering

  

• easy custom filtering

  

• logs are printed only for debug mode, so in the production compiler stripes out the logger code

• plain arguments can be passed without being forced to use string interpolation such as "\(myObject)"

• supports interactive metadata

  

Cons

• Location info (such as: line number, function and file) are passed to the system Logger as category, so it requires that each log creates new instance of the Logger. Potentially this could be a problem, however any performance issues were not encountered yet.

  For now location info as category, brings interactivity to show/hide it at any point of time. Anyway, this can be easily refactored if a true purpose for categorization is needed (i.e., by moving location info directly to the tag value and set optionally switchable via an extra environment variable).

Installation SPM

Add Package Dependency... and paste the URL of this repo: https://github.com/baquaz/AppLogger.git

Requirements

Platform	Minimum version
iOS	14
macOS	11

Add Xcode Environment Variable: ENABLE_APP_LOGGER and set value true or false to handle the logs.

By default, if the variable is missing, the logs are disabled and there is a warning printed in the console.

Usage

To make life easier start with defining global type alias.

// AppDelegate.swift

import AppLogger

typealias Applog = AppLogger

This way we can add logs across entire project without having to import AppLogger for each file in which we are going to use them.

Examples:

// simple log with default tag
Applog.print("Systems check completed.")

// simple log with explicit tag
Applog.print(tag: .debug, "The Jedi Temple remains secure. All is calm 📡")

struct Mission {
  let planet: String
  let daysETA: Int
  let commander: String
}

let mission = Mission(planet: "Dagobah", daysETA: 3, commander: "Master Yoda")

// log with multiple parameters and custom separator
Applog.print(tag: .network, 
             mission,
             "Waiting for approval...",
             separator: "\n")

Customization

In case there is a need to use custom tags there are LogType and LogStrategy protocols to be used.

LogType defines custom log tags.

public enum MyLogType: LogType {
  case info, critical
  
  public var label: String {
    switch self {
      case .info:
        "[MYCUSTOM_INFO ℹ️]"
      case .critical:
        "[MYCUSTOM_CRITICAL 🔥]"
    }
  }
}

Log Strategy defines how to print each log tag

import os

struct MyCustomLogStrategy: LogStrategy {
  var defaultLogType: LogType = MyLogType.info
  
  func log(message: String, tag: any LogType, category: String) {
    let logger = Logger(subsystem: Bundle.main.bundleIdentifier ?? "--", category: category)
    switch tag {
      case let tag as MyLogType:
        switch tag {
          case .info: logger.info("\(message)")
          case .critical: logger.critical("\(message)")
        }
      case let tag as DefaultLogType:
        // remap default logs
        switch tag {
          case .error: logger.fault("\(message)")
          case .warning: logger.warning("\(message)")
          case .success: logger.info("\(message)")
          case .debug: logger.debug("\(message)")
          case .network: logger.info("\(message)")
          case .simOnly: logger.info("\(message)")
        }
      default:
        logger.log("\(message)")
    }
  }
}

Usage

// set custom log strategy first
Applog.setLogStrategy(MyCustomLogStrategy())

Applog.printCustom("my custom default log")
Applog.printCustom(tag: MyLogType.critical, "my custom critical message")

Further customization

Applog.printCustom(tag: (any LogType)? = nil, ...) is a universal method to handle any type of custom log, so it always requires providing specified type of tag.

There is a way to target single type of custom LogType, by wrapping the printCustom function.

extension Applog {
  
  public static func printC(
    tag: MyLogType = .info,
    _ items: Any...,
    separator: String = " ",
    file: String = #file,
    function: String = #function,
    line: Int = #line)
  {
    Applog.printCustom(
      tag: .some(tag),
      items,
      separator: separator,
      file: file,
      function: function,
      line: line
    )
  }
} 

// now instead of using `Applog.printCustom(tag: MyLogType.critical, "my custom critical message")`
// just use wrapped function with short case value.
Applog.printC(tag: .critical, "my custom critical message")

References

Many claps 👏 to the author of this post:

https://medium.com/@alessandromanilii/custom-swift-logger-in-xcode15-19da40a058a5