iOS 如何决定使用什么[Sqlite、Realm、CoreData、User-default、JSON file]来存储数据

iOS开发中，数据的存储是一个非常重要的问题。根据实际应用场景的不同，我们可以选择使用不同的存储方式，包括Sqlite、Realm、CoreData、User-default和JSON文件等。那么，如何决定使用何种存储方式呢？

swift
import SQLite
// 创建数据库连接
let db = try! Connection("/path/to/database.sqlite")
// 创建备忘录表
let notes = Table("notes")
let id = Expression("id")
let title = Expression("title")
let content = Expression("content")
try! db.run(notes.create { t in
    t.column(id, primaryKey: true)
    t.column(title)
    t.column(content)
})
// 插入备忘录数据
let insert = notes.insert(title <- "Shopping", content <- "Buy milk and eggs")
try! db.run(insert)
// 查询备忘录数据
for note in try! db.prepare(notes) {
    print("Title: \(note[title]), Content: \(note[content])")
}

swift
import RealmSwift
// 定义备忘录数据模型
class Note: Object {
    @objc dynamic var title = ""
    @objc dynamic var content = ""
}
// 创建Realm数据库
let realm = try! Realm()
// 插入备忘录数据
let note = Note()
note.title = "Shopping"
note.content = "Buy milk and eggs"
try! realm.write {
    realm.add(note)
}
// 查询备忘录数据
let notes = realm.objects(Note.self)
for note in notes {
    print("Title: \(note.title), Content: \(note.content)")
}

swift
import CoreData
// 创建NSManagedObjectModel
let modelURL = Bundle.main.url(forResource: "Model", withExtension: "momd")!
let model = NSManagedObjectModel(contentsOf: modelURL)!
// 创建NSPersistentStoreCoordinator
let coordinator = NSPersistentStoreCoordinator(managedObjectModel: model)
let url = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).last!.appendingPathComponent("data.sqlite")
try! coordinator.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: url, options: nil)
// 创建NSManagedObjectContext
let context = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType)
context.persistentStoreCoordinator = coordinator
// 创建备忘录实体
let noteEntity = NSEntityDescription.entity(forEntityName: "Note", in: context)!
let note = NSManagedObject(entity: noteEntity, insertInto: context)
note.setValue("Shopping", forKey: "title")
note.setValue("Buy milk and eggs", forKey: "content")
try! context.save()
// 查询备忘录数据
let fetchRequest = NSFetchRequest(entityName: "Note")
let notes = try! context.fetch(fetchRequest) as! [NSManagedObject]
for note in notes {
    print("Title: \(note.value(forKey: "title")), Content: \(note.value(forKey: "content"))")
}

swift
// 存储备忘录数据
UserDefaults.standard.set("Shopping", forKey: "title")
UserDefaults.standard.set("Buy milk and eggs", forKey: "content")
// 读取备忘录数据
if let title = UserDefaults.standard.string(forKey: "title"),
   let content = UserDefaults.standard.string(forKey: "content") {
    print("Title: \(title), Content: \(content)")
}

swift
// 定义备忘录数据
let note = [
    "title": "Shopping",
    "content": "Buy milk and eggs"
]
// 将数据转化为JSON格式
let jsonData = try! JSONSerialization.data(withJSONObject: note, options: .prettyPrinted)
// 写入JSON文件
let fileURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).last!.appendingPathComponent("note.json")
try! jsonData.write(to: fileURL)
// 读取JSON文件
let data = try! Data(contentsOf: fileURL)
if let note = try! JSONSerialization.jsonObject(with: data, options: []) as? [String: Any] {
    if let title = note["title"] as? String,
       let content = note["content"] as? String {
        print("Title: \(title), Content: \(content)")
    }
}