Swift string types and common methods detailed explanation

// Direct assignmenttext = ""

// 1. Constructing methodtext = String() // ""
// String constructiontext = String("William") // "William"
// Integer structuretext = String(888) // "888"
// Floating point structuretext = String(8.88) // "8.88"
// Character constructiontext = String("a") // "a"
// Boolean structuretext = String(true) // "true"
// Tuple constructiontext = String(describing: (5, 5.0, true)) // "(5, 5.0, true)"
// List constructiontext = String(describing: [1, 2, 3, 4]) // "[1, 2, 3, 4]"
// Format stringtext = String(format: "Hello, %@", "William") // "Hello, William"

var text1 = "hello, "
var text2 = "William"
var result = text1 + text2
print(result) // hello, William

// 3. Insert a simple value into a string using \() , similar to ${} in Kotlinvar target = "Hello, \(66)" // Hello, 66

var target2 = "Hello, \(text2)" // Hello, William

var target3 = "Hello, \(1 + 2)" // hellow, 3

var char : Character = "e" // "e"
var char2 = Character("e") // "e"
// Takes up 16 bytesvar size = MemoryLayout<Character>.size // 16
// Character arrayvar array : [Character] = ["W", "i", "l", "l", "i", "a", "m"]
// Construct Stringvar newStr = String(array) // William
// traverse stringslet city = "Shanghai"
for cha in city {
    print(cha)
}

// \0: indicates a blank sign// \\: means backslash// \t: indicates tab characters// \n: indicates line break// \r: means carriage return// \': means single quotes// \": means double quotes// \u{}: Create characters with Unicode codevar code = "\u{0068}\u{0065}\u{006c}\u{006c}\u{006f}" // hello
var escapeChar = "Blank character:\0 backslash:\\tTab character:\tLine newline character\nCarriage return character:\rSingle quotes:\'Double quotes:\""
print(escapeChar)

// string is emptyvar emptyStr = ""
if  {
    print("string is empty")
}
if  == 0 {
    print("string count is 0")
}

// The character size will be compared one by one.let str1 = "100a", str2 = "101a"
if (str1 < str2) {
    print("str1 < str2")
}
// The strings are judged equally, and the positions of all characters are compared to be equal to the strings.if (str1 == str2) {
    print("str1 < str2")
}

// Use subscript to access charactersvar indexStr = "Hello, William"
// Get the starting subscriptvar startIndex:  = 
var endIndex:  = 
// Get the character corresponding to a subscript after a subscriptvar afterChar = indexStr[(after: startIndex)] // e
// Get the character corresponding to the previous subscript of a subscriptvar beforeChar = indexStr[(before: endIndex)] // m

// ... operator specifies the range, moves 4 bits backward from startIndex to intercept substringvar subStr = indexStr[startIndex...(startIndex, offsetBy: 4)] // hello
// Move 7 bits forward from endIndex to intercept substringvar subStr2 = indexStr[(endIndex, offsetBy: -7)..<endIndex] // William

// Get rangevar range = (of: "Hello")
// Append string(Character("."))
(" append string") // Hello, William. append string

// Insert a single character to the specified position Hello, William.# append string("#", at: (startIndex, offsetBy: 15))

// Insert a set of characters Hello, William.-#-# append string(contentsOf: ["-", "#", "-"], at: (startIndex, offsetBy: 15))

// Replace the string in the specified range How are you.-#-# append string(startIndex...(startIndex, offsetBy: 13), with: "How are you")

// Delete a single character in the specified location How are you.-#-# append strin(at: (before: ))

// Delete the specified range -#-# append string(...(, offsetBy: 11))

// Delete all characters ""()

// Convert casevar uppercase = "hello, swift".uppercased() // HELLO, SWIFT
var lowercase = "HELLO, SWIFT".lowercased() // hello, swift

// Check the suffixvar hasPrefix = ("he") // false
var hasSuffix = ("ft") // true