Prevent sleep and screensaver while the application running. ref: http://qiita.com/asus4/items/02b5096a937bbd419f3e

LittleCaffeine.h

//
//  LittleCaffeine.h
//
//  This is tiny utility inspired by Caffeine http://lightheadsw.com/caffeine/
//
//  Created by Koki Ibukuro on 2014/04/01.
//  Copyright (c) 2014年 Koki Ibukuro. All rights reserved.
//

#pragma once

#ifndef Little_Caffeine_h
#define Little_Caffeine_h

#import <Foundation/Foundation.h>
#import <IOKit/pwr_mgt/IOPMLib.h>

static IOPMAssertionID assertionID;

static BOOL LittleCaffeineEnable() {

    // https://developer.apple.com/library/mac/qa/qa1340/_index.html

    CFStringRef reasonForActivity= CFSTR("Little Caffeine for Wake Up");
    IOReturn success = IOPMAssertionCreateWithName(kIOPMAssertionTypeNoDisplaySleep,
                                                   kIOPMAssertionLevelOn, reasonForActivity, &assertionID);

    if (success == kIOReturnSuccess) {
        return YES;
    }
    else {
        assertionID = -1;
        return NO;
    }
}

static BOOL LittleCaffeineDisable() {
    IOReturn success = NO;
    if(assertionID > 0) {
        success = IOPMAssertionRelease(assertionID);
    }

    if(success == kIOReturnSuccess) {
        return YES;
    }
    else {
        return NO;
    }
}

#endif

LittleCaffeine.swift

//
//  LittleCaffeine.swift
//
//  This is tiny utility inspired by Caffeine http://lightheadsw.com/caffeine/
//
//  Created by Koki Ibukuro on 2024/03/11
//  Copyright (c) 2024 Koki Ibukuro. All rights reserved.
//

import IOKit.pwr_mgt

struct LittleCaffeine {
    private static var assertionID: IOPMAssertionID = .init(0)

    static func Enable() -> Bool {
        let reasonForActivity = "Little Caffeine for Wake Up" as CFString
        let success = IOPMAssertionCreateWithName(kIOPMAssertPreventUserIdleDisplaySleep as CFString,
                                                  IOPMAssertionLevel(kIOPMAssertionLevelOn),
                                                  reasonForActivity,
                                                  &assertionID)
        if success == kIOReturnSuccess {
            return true
        } else {
            assertionID = IOPMAssertionID(0)
            return false
        }
    }

    static func Disable() -> Bool {
        var success = kIOReturnError
        if assertionID > 0 {
            success = IOPMAssertionRelease(assertionID)
            assertionID = IOPMAssertionID(0)
        }
        return success == kIOReturnSuccess
    }
}

SampleAppDelegate.m

#import "LittleCaffeine.h"

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{    
    LittleCaffeineEnable();
}


- (void) applicationWillTerminate:(NSNotification *)notification
{
    LittleCaffeineDisable();
}