Swift vs Objective-C

iOS Application Project

We can write both Swift and Objective-C at the same project.
Certainly, we have to decide base project language.(Objective-C, Swift)
But, we can call each other to use Bridge Header, or Swift Header

Example(Combined)

Objective-C base AppDelegate.m

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // Override point for customization after application launch.
    
    // Objective-C
    //self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    //self.window.rootViewController = [[ObjcViewController alloc] init];
    //[self.window makeKeyAndVisible];
    
    // Swift
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    self.window.rootViewController = [[SwiftViewController alloc] init];
    [self.window makeKeyAndVisible];
    
    return YES;
}

Objective-C ViewController Example
Header

#import <UIKit/UIKit.h>
@interface ObjcViewController : UIViewController
@end

Code

#import "ObjcViewController.h"

@interface ObjcViewController ()

@property (nonatomic) UIImageView *imageView;
@property (nonatomic) UILabel *titleLabel;

@end

@implementation ObjcViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor whiteColor];
    
    self.imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"SteveJobs"]];
    self.titleLabel = [[UILabel alloc] init];
    self.titleLabel.text = @"Stay hungry, stay foolish!";
    self.titleLabel.textAlignment = NSTextAlignmentCenter;
    [self.view addSubview:self.imageView];
    [self.view addSubview:self.titleLabel];
}

- (void)viewWillLayoutSubviews {
    CGRect frame = self.view.frame;
    
    self.imageView.frame = CGRectMake((frame.size.width - 200.0) / 2.0, 100, 200, 100);
    self.titleLabel.frame = CGRectMake(0, CGRectGetMaxY(self.imageView.frame), frame.size.width, 40);
}
@end

Swift ViewController Example

import Foundation
import UIKit

@objc class SwiftViewController : UIViewController {
    
    private var imageView : UIImageView?
    
    private var titleLabel : UILabel?
    
    override func viewDidLoad() {
        self.view.backgroundColor = UIColor.whiteColor()
        
        self.imageView = UIImageView(image: UIImage(named: "SteveJobs"))
        self.titleLabel = UILabel()
        self.titleLabel?.text = "Stay swift, stay foolish!"
        self.titleLabel?.textAlignment = .Center
        
        self.view.addSubview(self.imageView!)
        self.view.addSubview(self.titleLabel!)
    }
    
    override func viewWillLayoutSubviews() {
        let frame : CGRect = self.view.frame
        
        self.imageView?.frame = CGRectMake((frame.width - 200) / 2.0, 100, 200, 100)
        self.titleLabel?.frame = CGRectMake(0, CGRectGetMaxY((self.imageView?.frame)!), frame.width, 40)
    }
}

Swift is not need to create header file

Swift

• Swift still uses ARC(Automatic Reference
• Swift is faster(Run level, Compiler level) than swift
• we can call each other, Swift can call Objective-C class, Objective-C can call Swift class(Objective-C support class)
• UIKit(iOS UI base class) is still Objective-C

Swift Compiler is optimised compare to Objective-C
This is the reason that Swift is faster.