A convenient Swift protocol and wrapper for OSLog.

Logging.swift

import os

private let subsystem = "<ENTER-YOUR-SUBSYSTEM-STRING-HERE>"

// MARK: - Protocol

protocol LogProducer {
    func debug(_ message: StaticString, _ messageArguments: CVarArg...)
    func info(_ message: StaticString, _ messageArguments: CVarArg...)
    func warn(_ message: StaticString, _ messageArguments: CVarArg...)
    func fault(_ message: StaticString, _ messageArguments: CVarArg...)
    func error(_ message: StaticString, _ messageArguments: CVarArg...)
}

// MARK: - Implementation

/// A convenience wrapper for `OSLog`
struct Logger: LogProducer {
    private let log: OSLog
    
    init(_ category: String) {
        self.log = OSLog(subsystem: subsystem, category: category)
    }
    
    // MARK: Log Methods
    
    // LOL, this method sucks ATM since Swift doesn't allow the forwarding of variadic params.
    private func log(_ message: StaticString, _ type: OSLogType, _ messageArguments: [CVarArg]) {
        switch messageArguments.count {
            case 0:
                os_log(message, log: log, type: type)
            case 1:
                os_log(message, log: log, type: type, messageArguments[0])
            case 2:
                os_log(message, log: log, type: type, messageArguments[0], messageArguments[1])
            case 3:
                os_log(message, log: log, type: type, messageArguments[0], messageArguments[1], messageArguments[2])
            case 4:
                os_log(message, log: log, type: type, messageArguments[0], messageArguments[1], messageArguments[2], messageArguments[3])
            case 5:
                os_log(message, log: log, type: type, messageArguments[0], messageArguments[1], messageArguments[2], messageArguments[3], messageArguments[4])
            default:
                os_log("Too many variadic params were sent to the logger so we tossed them!", log: log, type: .error)
                os_log(message, log: log, type: type)
        }
    }
    
    func debug(_ message: StaticString, _ messageArguments: CVarArg...) {
        log(message, .debug, messageArguments)
    }
    
    func info(_ message: StaticString, _ messageArguments: CVarArg...) {
        log(message, .info, messageArguments)
    }
    
    func warn(_ message: StaticString, _ messageArguments: CVarArg...) {
        log(message, .default, messageArguments)
    }
    
    func fault(_ message: StaticString, _ messageArguments: CVarArg...) {
        log(message, .fault, messageArguments)
    }
    
    func error(_ message: StaticString, _ messageArguments: CVarArg...) {
        log(message, .error, messageArguments)
    }
}