Swift Documentation For Me

Variables

Var

var name = "Pejman"     // String
var age = 21            // Int

age = age + 1           // age = 22
age = 23                // age = 23 
age = "twenty-three"    // Error

Const

let name = "Pejman"     // String
name = "Pezhman"      // Error (Constants values can't changed)

Loops

Loop structures in swift

For loop

for i in 1...5 {
	print(i)
}
/* --- output --- */
/* 1
 * 2
 * 3
 * 4
 * 5
 */

While loop

while condition {
		// do something
}

Datatype conversion

// Convert other datatypes to String
// var num = 23
// var isOn = false
Text("Method 1: \(String(isOn)). \(String(num))")    
Text("Method 2: \(isOn).. \(num)" as String)
Text(verbatim: "Method 3: \(isOn)... \(num)")

Views

My First App

import SwiftUI

struct pythonView: View {
    var body: some View {
        VStack {
            HStack {
                Image("python")     // in Assets Folder
                    .resizable()
                    .scaledToFit()
                VStack {
                    Text("Python")
                        .font(.title)
                        .foregroundColor(.blue)
                    Text("A programming language that can do anything!")
                        .font(.caption)
                        .foregroundColor(.yellow)
                }
            }
        }
    }
}

struct pythonView_Previews: PreviewProvider {
    static var previews: some View {
        pythonView()
    }
}

Output

view.png

Keep on with Apps

Data Separation

  • Always Define variables outside of View body

struct ConditionalViews: View {
		@State var isOn = false       // Correct
    var body: some View {
		@State var isOn = false   // Wrong
        VStack {
			...
		}
	}
}

State Variables

In the Previous Example, there is a @State before defining a variable; if you want to change UI and View via Variables, this is how to do it.

@State is a property wrapper

Ternary conditional operation

Circle()
	.foregroundColor( isOn ? .yellow : .black )

if isOn = true Circle is yellow else it’ll be black

  • Example

Circle()
	.frame(maxHeight: 200)
    .foregroundColor( isOn ? .yellow : .black )
    .shadow(color: isOn ? .orange : .gray, radius: isOn ? 50 : 10 )   

import SwiftUI

struct ConditionalCircle: View {
    @State var isOn = false
    
    var body: some View {
        VStack {
            Circle()
                .frame(maxHeight: 200)
                .foregroundColor( isOn ? .yellow : .black )
                .shadow(color: isOn ? .orange : .gray, radius: isOn ? 50 : 10 )
                .scaleEffect( isOn ? 1.5 : 0.75)
                .animation(.default, value: isOn)
            

            Button("Press Me") {
                isOn.toggle()
            }
        }
    }
}

struct SwiftUIView_Previews: PreviewProvider {
    static var previews: some View {
        ConditionalCircle().assess()
    }
}

Button.gif

GitHub

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