Learn SwiftUI (Day 1/100)

Swift

• Variable
• Constants
• String and multiple-line string
• Integer
• Double

import Cocoa

// "var" means make a new variable
var greeting = "Hello, playground"
print(greeting)
var name = "hello"
print(name)
name = "world"
print(name)

// let: Declares a constant that cannot be changed once it has been set, i.e., an immutable variable
let lang = "python"
print(lang)
// lang = "java" // Error: cannot assign to value
// print(lang)

/*
 Best practice suggests that you should default to using let to define a variable and only use var when you explicitly need the variable’s value to change. This helps lead to cleaner, more predictable code.
 */

// ## Create strings

let quote = "Then he tapped a sign \"Believe\" and walked away"
// multiple line string
let movie = """
hello
世界
"""
print(movie)
print(movie.count) // 8 -> count returnes unicode count
let trimmed = movie.trimmingCharacters(in: .whitespacesAndNewlines)
print(trimmed.count)

// define integers
let score = 10
print(score / 3) // 3
var points = 10
points += 1
print(points)

// define floating number
let number = 0.1 + 0.2
print(number)

let a = 1
let b = 2.0
// int and double cannot sum, must cast first
let c = Double(a) + b
let d = a + Int(b)