데이터 읽기와 쓰기

데이터 읽기 및 쓰기

문자열 쓰기

import Foundation

let url = URL(fileURLWithPath: "/tmp/hello.txt")
try? "Hello, file!".write(to: url, atomically: true, encoding: .utf8)
print("Wrote string to disk")

문자열 읽기

import Foundation

let url = URL(fileURLWithPath: "/tmp/hello.txt")
if let text = try? String(contentsOf: url, encoding: .utf8) {
    print(text)
}

데이터 다루기

import Foundation

let url = URL(fileURLWithPath: "/tmp/hello.txt")
if let data = try? Data(contentsOf: url) {
    print("Byte count: \(data.count)")
}

데이터 쓰기

import Foundation

let bytes = Data([0x48, 0x69])
let url = URL(fileURLWithPath: "/tmp/bytes.bin")
try? bytes.write(to: url)
print("Wrote raw data")

데이터에서 문자열로 변환

import Foundation

let data = Data([0x48, 0x69])
if let s = String(data: data, encoding: .utf8) {
    print(s)
}

JSON 인코딩

import Foundation

struct Note: Codable { let text: String }
let data = try? JSONEncoder().encode(Note(text: "hi"))
let url = URL(fileURLWithPath: "/tmp/note.json")
try? data?.write(to: url)
print("Saved JSON")

JSON 디코딩

import Foundation

struct Note: Codable { let text: String }
let url = URL(fileURLWithPath: "/tmp/note.json")
if let data = try? Data(contentsOf: url),
   let note = try? JSONDecoder().decode(Note.self, from: data) {
    print(note.text)
}

원자적 쓰기

import Foundation

let url = URL(fileURLWithPath: "/tmp/safe.txt")
try? "important".write(to: url, atomically: true, encoding: .utf8)
print("Atomic write done")

오류 처리

import Foundation

let url = URL(fileURLWithPath: "/does/not/exist.txt")
do {
    _ = try String(contentsOf: url, encoding: .utf8)
} catch {
    print("Read failed: \(error.localizedDescription)")
}

추가와 덮어쓰기

import Foundation

let url = URL(fileURLWithPath: "/tmp/log.txt")
if let handle = try? FileHandle(forWritingTo: url) {
    handle.seekToEndOfFile()
    handle.write(Data("line\n".utf8))
    try? handle.close()
}
print("Appended")

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