iOS Development Tutorial: Creating a Demo Project, Implementing Views, Buttons, and Images with Swift and Comparing to Objective‑C

The article introduces a series of iOS development tutorials that cover the entire workflow from tool usage to app store release, beginning with a brief statement of the learning goal.

Requirements: display an orange‑yellow rectangle, add a clickable button with an event handler, and show an image at the center of the screen.

System versions: macOS 10.15.5, Xcode 11.5.

1. Create Demo Project

1.1 Choose Xcode Project

Start a new Xcode project and select Single View App .

1.2 Select Single View App

Proceed with the default settings to generate the project skeleton.

2. Code Implementation

2.1 Application Entry Point

The @UIApplication annotation in AppDelegate.swift marks the class as the app’s entry point.

2.2 Code Structure

All methods are placed inside a pair of braces with indentation, similar to Java.

2.3 Feature Implementation

2.3.1 Create a View and Add a Yellow Rectangle

import UIKit

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        // 1. Create a view
        let v = UIView(frame: CGRect(x:0, y:0, width:100, height:100))
        // 2. Set background color
        v.backgroundColor = UIColor.yellow
        // 3. Add to current view
        view.addSubview(v)
    }
}

The result is a yellow rectangle positioned at the top‑left corner.

2.3.2 Add a Button with Click Event

// 2. Create a button
let btn = UIButton(type: .contactAdd)

// 2.1 Add to current view
v.addSubview(btn)

// 2.2 Add click event
btn.addTarget(self, action: #selector(btnClick), for: .touchUpInside)

// 2.3 btnClick method logs output

A button appears at the top‑left; tapping it prints a log message.

2.3.3 Add an Image

// 3.1 Add an image view
let iv = UIImageView(image: #imageLiteral(resourceName: "2.jpeg"))

// 3.2 Center the image
iv.center = view.center

The image is displayed in the center of the screen.

3. Swift vs. Objective‑C Syntax Comparison

3.1 Creating a View

Swift: UIView(XXX:)
OC: [[UIView alloc] initWithXXX:]

3.2 Class Method

Swift: UIColor.yellow
OC: [UIColor yellow]

3.3 Accessing Self

It is recommended to omit self. unless required by the compiler, such as inside closures.

3.4 Semicolon Usage

Semicolons are unnecessary unless multiple statements share a line.

3.5 Enum Types

Swift: type: .contactAdd
OC: UIButtonType.ContactAdd

3.6 Selector Syntax

Swift uses #selector (no colon for parameter‑less methods); Objective‑C uses @selector .

3.7 Debugging

Swift: print() (fast, no timestamp, use #function for method name). Objective‑C: NSLog (use __FUNCTION__ for method name).

4. Effective Use of Comments

Special comment tags like TODO , MARK , and FIXME create anchor points in the navigation bar, allowing quick jumps to annotated sections.