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Simple Logger

This snippet demonstrates how to create a custom logging utility in Swift, supporting different severity levels and providing context information.

Details

URL: 🔗 https://gist.github.com/aryamansharda/d153667b25e03eef9b0ac71de43e801b#file-log-swift

Source: 🔗 Ace the iOS Interview

Author: Aryaman Sharda

Tags:
Swift, Logging, Debugging

Platforms Supported: iOS, macOS

Swift Version: 5.0 and above

Key Points​

  • Supports multiple severity levels (info, warning, error).
  • Provides context information (file name, function name, line number).
  • Uses compiler directives to ensure logging only in debug mode.

Use Cases​

  • Enhancing debugging by providing detailed log messages.
  • Differentiating log messages by severity level.
  • Avoiding logging sensitive information in production builds.

Alternative Approaches​

  • Using third-party logging frameworks like CocoaLumberjack.
  • Implementing logging with OSLog for performance and privacy.
  • Utilizing external logging services for advanced log management.

Performance Considerations​

  • Using compiler directives to avoid logging in production improves performance.
  • Context-aware logging helps in identifying issues faster during development.
  • Minimal overhead due to selective logging based on build configurations.

Code​

import Foundation

enum LogLevel {
    case info
    case warning
    case error
    
    fileprivate var prefix: String {
        switch self {
        case .info: return "INFO"
        case .warning: return "WARN ⚠"
        case .error: return "ALERT ❌"
        }
    }
}

struct Context {
    let file: String
    let function: String
    let line: Int
    
    var description: String {
        "\((file as NSString).lastPathComponent):\(line) \(function)"
    }
}

enum Log {
    static func info(_ str: StaticString, shouldLogContext: Bool = true, file: String = #file, function: String = #function, line: Int = #line) {
        let context = Context(file: file, function: function, line: line)
        handleLog(level: .info, str: str.description, shouldLogContext: shouldLogContext, context: context)
    }
    
    static func warning(_ str: StaticString, shouldLogContext: Bool = true, file: String = #file, function: String = #function, line: Int = #line) {
        let context = Context(file: file, function: function, line: line)
        handleLog(level: .warning, str: str.description, shouldLogContext: shouldLogContext, context: context)
    }
    
    static func error(_ str: StaticString, shouldLogContext: Bool = true, file: String = #file, function: String = #function, line: Int = #line) {
        let context = Context(file: file, function: function, line: line)
        handleLog(level: .error, str: str.description, shouldLogContext: shouldLogContext, context: context)
    }
    
    fileprivate static func handleLog(level: LogLevel, str: String, shouldLogContext: Bool, context: Context) {
        let logComponents = ["[\(level.prefix)]", str]
        var fullString = logComponents.joined(separator: " ")
        
        if shouldLogContext {
            fullString += " ➜ \(context.description)"
        }
        
        #if DEBUG
        print(fullString)
        #endif
    }
}

References​

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