深入讲解Swift中的模式匹配

enum Result {
 case success
 case failure
}

let result = Result.success

if case .success = result {
 print("Value of result is success.")
}

let optionalInt: Int? = 1

if let val = optionalInt {
 print("The value of optionalInt is (val)")
}
func handleGuard() {
 guard let val = optionalInt else {
 return
 }
 print("The value of optionalInt is (val)")
}
handleGuard()

if case .some(let val) = optionalInt {
 print("The value of optionalInt is (val)")
}

if case let val? = optionalInt {
 print("The value of optionalInt is (val)")
}

let values: [Int?] = [1, nil, 3, nil, 5, nil, 7, nil, 9, nil]

for val in values {
 print("Value in values is (String(describing: val))")
}

var valuesIterator = values.makeIterator()
while let val = valuesIterator.next() {
 print("Value in values is (String(describing: val))")
}

for val in values.compactMap({ $0 }) {
 print("Value in values is (val)")
}

for case let val? in values {
 print("Value in values is (val)")
}

valuesIterator = values.makeIterator()
while let val = valuesIterator.next(), val != nil {
 print("Value in values is (String(describing: val))")
}

let results: [Result] = [.success, .failure]
for case .success in results {
 print("Values in results contains success.")
 break
}

enum NetResource {
 case http(resource: String)
 case ftp(resource: String)
}

let nets: [NetResource] = [.http(resource: "https://www.baidu.com"), .http(resource: "https://www.apple.cn"), .ftp(resource: ftp://192.0.0.1)]

for case .http(let resource) in nets {
 print("HTTP resource (resource)")
}

for notNilValue in values where notNilValue != nil {
 print("Not nil value: (String(describing: notNilValue!))")
}

let rangeValues = Array(0...999)
for threeDivideValue in rangeValues where threeDivideValue % 3 == 0 {
 print("Three devide value: (threeDivideValue)")
}

for containsThree in rangeValues where String(containsThree).contains("3") {
 print("Value contains three: (containsThree)")
}

let value = 188

switch value {
case 0..<50:
 print("The value is in range [0, 50)")
case 50..<100:
 print("The value is in range [50, 100)")
case 100..<150:
 print("The value is in range [100, 150)")
case 150..<200:
 print("The value is in range [150, 200)")
case 200...:
 print("The value is in range [200, ")
default: break
}

// The value is in range [150, 200)

let tuples: (Int, String) = (httpCode: 404, status: "Not Found.")

switch tuples {
case (400..., let status):
 print("The http code is 40x, http status is (status)")
default: break
}

let somePoint = (1, 1)

switch somePoint {
case (0, 0):
 print("(somePoint) is at the origin")
case (_, 0):
 print("(somePoint) is on the x-axis")
case (0, _):
 print("(somePoint) is on the y-axis")
case (-2...2, -2...2):
 print("(somePoint) is inside the box")
default:
 print("(somePoint) is outside of the box")
}

switch tuples {
case (404, _):
 print("The http code is 404 not found.")
default: break
}

let yetAnotherPoint = (1, -1)
switch yetAnotherPoint {
case let (x, y) where x == y:
 print("((x), (y)) is on the line x == y")
case let (x, y) where x == -y:
 print("((x), (y)) is on the line x == -y")
case let (x, y):
 print("((x), (y)) is just some arbitrary point")
}

for notNilValue in values {
 if notNilValue != nil {
  print("Not nil value: (String(describing: notNilValue!))")
 }
}