معلمات in-out ومعالجة الأخطاء الأساسية (throws)

مقدمة

أساسيات inout

func increment(_ value: inout Int) {
    value += 1   // mutate caller's variable
}
var count = 0
increment(&count)
print("count =", count)  // 1

متى تُستخدم

throws + do/catch

enum FileError: Error { case notFound, unreadable }

func readFile(named: String) throws -> String {
    if named.isEmpty { throw FileError.notFound }
    return "contents of \\(named)"
}

// Calling a throwing function
do {
    let text = try readFile(named: "notes.txt")
    print(text)
} catch {
    print("Failed:", error)
}

try? مقابل try!

// try? converts errors to nil (optional)
let maybeText = try? readFile(named: "")
print(maybeText as Any)  // nil

// try! crashes on error—only use when you are sure
// let forcedText = try! readFile(named: "")  // avoid in production

دوال مساعدة تُطلق الأخطاء

func parseInt(_ s: String) throws -> Int {
    if let n = Int(s) { return n }
    else { throw NSError(domain: "Parse", code: 1) }
}

do {
    let n = try parseInt("10")
    print("n =", n)
} catch {
    print("parse error")
}

سؤال عن inout

مراجعة