从sqlite文件SWIFT4.2加载数据

Question

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我在sqlite中有大型数据库，所以我试图从我的data.sqlite文件中直接访问它，但是我无法访问它。我过去用目标C完成了那项任务

采取的步骤：

1:将data.sqlite文件拖到项目中

2:尝试通过fmdb访问它。

输出: /var/mobile/Containers/Data/Application/557B2961-52D8-4B14-BABC-BF4829852127/Documents/data.sqlite path===

let documentsDirectory = (NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0] as NSString) as String 
pathToDatabase = documentsDirectory.appending("/(databaseFileName)")

func openDatabase() -> Bool {
 print("path=== \(pathToDatabase ?? "empty")")
      if database == nil {
           if FileManager.default.fileExists(atPath: pathToDatabase) {
                database = FMDatabase(path: pathToDatabase) 
//code is not entering in that if , it should be there becasuse I already included my sqlitefile    
 } 
        if database != nil {
            if database.open() {
                return true
            }
        }
        return false
    }

Answer 1

我没有使用fmdb，但是我在最近的一个项目中成功地使用了GRDB (https://github.com/groue/GRDB.swift)。通常，当出现错误时，这些库将允许您检索错误代码或日志输出，这可能对解决问题非常有用。

同时，下面是一个Swift函数，用于将文件名转换为完整的文档用户路径：

    private static func path(for filename: String) -> String {
        let fm = FileManager.default
        let documentsDirectory = fm.urls(for: .documentDirectory, in: .userDomainMask).first
        return documentsDirectory?.appendingPathComponent(filename).absoluteString ?? filename
    }

但是，请注意，作为构建的一部分包含的文件通常不在您的文档中，而是包资源的一部分。在这种情况下，这段代码可能更有用：

    let path = Bundle.main.path(forResource: "mydatabase", ofType: "sqlite")

Answer 2

如果本地数据库文件不存在，尝试将其复制到应用程序的文档库中。

import FMDB

class DBService {
    // MARK: Properties
    static let shared = DBService()
    var database: FMDatabase!

    private let fileManager = FileManager.default
    private var documentsDBPath: String
    private var resourcesDBPath: String

    private let databaseFileName = "data"
    private let databaseFileName = "sqlite"

    // MARK: Initializers
    private init() {
        documentsDBPath = try! fileManager
            .url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: false)
            .appendingPathComponent(databaseFileName)
            .appendingPathExtension(databaseFileExtension)
            .path

        resourcesDBPath = Bundle.main.path(forResource: databaseFileName,
                                           ofType: databaseFileExtension)!
    }

    // MARK: - Setup
    func isDatabaseOpen() -> Bool {
        if database == nil {
            initDatabase()
        }

        return database.open()
    }

    private func initDatabase() {
        if isFirstLaunch() {
            copyDatabase(from: resourcesDBPath, to: documentsDBPath)  
        }

        database = FMDatabase(path: documentsDBPath)
    }

    private func isFirstLaunch() -> Bool {
        return !fileManager.fileExists(atPath: documentsDBPath)
    }

    private func copyDatabase(from source: String, to destination: String) {
        do {
            try fileManager.copyItem(atPath: source, toPath: destination)
        } catch {
            debugPrint(error)
        }
    }
}

Answer 3

您的文件显然不在文档目录中，您应该在主包中访问它。

let dbUrl = Bundle.main.url(forResource: "data", withExtension: "sqlite")

如果需要在documents目录中复制数据库，请使用以下命令

let fileManager = FileManager.default
let dbUrl = fileManager.urls(for: .documentDirectory, in: .userDomainMask).last!.appendingPathComponent("data.sqlite")
if !fileManager.fileExists(atPath: dbUrl.path) {
    let url = Bundle.main.url(forResource: "data", withExtension: "sqlite")!
    try? fileManager.copyItem(at: url, to: dbUrl)
}

使用

let database = FMDatabase(url: dbUrl)