Đọc và Ghi File

1. Giới thiệu

Swift sử dụng FileManager và String/Data để làm việc với files.

2. Lấy đường dẫn

import Foundation

// Documents directory
let documentsPath = FileManager.default.urls(
    for: .documentDirectory,
    in: .userDomainMask
)[0]

// Tạo file path
let filePath = documentsPath.appendingPathComponent("data.txt")
print(filePath.path)

3. Ghi file text

let text = "Hello, Swift!"
let filePath = documentsPath.appendingPathComponent("greeting.txt")

do {
    try text.write(to: filePath, atomically: true, encoding: .utf8)
    print("File written successfully")
} catch {
    print("Error writing file: \(error)")
}

4. Đọc file text

let filePath = documentsPath.appendingPathComponent("greeting.txt")

do {
    let content = try String(contentsOf: filePath, encoding: .utf8)
    print(content)
} catch {
    print("Error reading file: \(error)")
}

5. Ghi Data (Binary)

let data = "Binary content".data(using: .utf8)!
let filePath = documentsPath.appendingPathComponent("data.bin")

do {
    try data.write(to: filePath)
} catch {
    print("Error: \(error)")
}

6. Đọc Data

do {
    let data = try Data(contentsOf: filePath)
    if let content = String(data: data, encoding: .utf8) {
        print(content)
    }
} catch {
    print("Error: \(error)")
}

7. FileManager Operations

let fileManager = FileManager.default

// Kiểm tra tồn tại
if fileManager.fileExists(atPath: filePath.path) {
    print("File exists")
}

// Xóa file
try? fileManager.removeItem(at: filePath)

// Copy file
try? fileManager.copyItem(at: source, to: destination)

// Move file
try? fileManager.moveItem(at: source, to: destination)

8. Làm việc với Directories

let fileManager = FileManager.default
let newDir = documentsPath.appendingPathComponent("MyFolder")

// Tạo directory
try? fileManager.createDirectory(
    at: newDir,
    withIntermediateDirectories: true,
    attributes: nil
)

// Liệt kê files
if let contents = try? fileManager.contentsOfDirectory(atPath: newDir.path) {
    for item in contents {
        print(item)
    }
}

9. File Attributes

let filePath = documentsPath.appendingPathComponent("data.txt")

if let attributes = try? fileManager.attributesOfItem(atPath: filePath.path) {
    let size = attributes[.size] as? Int64 ?? 0
    let modDate = attributes[.modificationDate] as? Date

    print("Size: \(size) bytes")
    print("Modified: \(modDate?.description ?? "Unknown")")
}

10. Codable với JSON File

struct User: Codable {
    let name: String
    let age: Int
}

// Ghi JSON
let user = User(name: "Alice", age: 25)
let filePath = documentsPath.appendingPathComponent("user.json")

do {
    let encoder = JSONEncoder()
    encoder.outputFormatting = .prettyPrinted
    let data = try encoder.encode(user)
    try data.write(to: filePath)
} catch {
    print("Error: \(error)")
}

// Đọc JSON
do {
    let data = try Data(contentsOf: filePath)
    let user = try JSONDecoder().decode(User.self, from: data)
    print(user)
} catch {
    print("Error: \(error)")
}

---

📝 Tóm tắt

• FileManager cho file operations
• String.write(to:) ghi text
• String(contentsOf:) đọc text
• Data.write(to:) ghi binary
• Data(contentsOf:) đọc binary
• try-catch cho error handling
• Codable cho JSON persistence