Question

我需要将我的bundle资源中的SQLite文件预加载到应用程序支持目录中。我想确保存在正确的文件与默认情况下Core Data放在那里的空文件。为此，我使用FileManager.default.contentsEqual;但是，这总是返回false。

我尝试使用游乐场进行测试，但副本中创建的是别名文件，仍然会进行false比较。

在应用程序中，文件会以相同的名称和大小进行复制。日期不同：副本具有当前日期/时间而不是原始时间戳。但是，使用contentsEqual，我认为不重要。

更新： diff在命令行显示文件是相同的......

我错过了什么？

这里是操场上的代码，与我的应用代码几乎相同：

// get the URL for the application support directory
let appSupportDir: URL = try!
 FileManager.default.url(for: FileManager.SearchPathDirectory.applicationSupportDirectory,
                         in: FileManager.SearchPathDomainMask.userDomainMask,
                         appropriateFor: nil, create: true)

// get the source URLs for the preload files
let sqliteFileBundleURL: URL = Bundle.main.url(forResource: "My_DB", withExtension: "sqlite")!
let sqliteShmFileBundleURL: URL = Bundle.main.url(forResource: "My_DB", withExtension: "sqlite-shm")!
let sqliteWalFileBundleURL: URL = Bundle.main.url(forResource: "My_DB", withExtension: "sqlite-wal")!

// create target URLs for copy to application support directory
let sqliteFileAppSptURL: URL = appSupportDir.appendingPathComponent("My_DB.sqlite")
let sqliteShmFileAppSptURL: URL = appSupportDir.appendingPathComponent("My_DB.sqlite-shm")
let sqliteWalFileAppSptURL: URL = appSupportDir.appendingPathComponent("My_DB.sqlite-wal")

// remove the files if they already exist at the target (for test - app doesn't do this)
do {
    let filesFound: [URL] = try FileManager.default.contentsOfDirectory(at: appSupportDir,
                                                                    includingPropertiesForKeys: nil,
                                                                    options: .skipsHiddenFiles)
    if !filesFound.isEmpty {
        for fileURL in filesFound {
            try FileManager.default.removeItem(at: fileURL)
        }
        print("Removed \(filesFound.count) files without error.")
    }
}
catch {
    print("Error:\n\(error)")
}

// copy the files to the application support directory
do {
    try FileManager.default.copyItem(at: sqliteFileBundleURL, to: sqliteFileAppSptURL)
    try FileManager.default.copyItem(at: sqliteShmFileBundleURL, to: sqliteShmFileAppSptURL)
    try FileManager.default.copyItem(at: sqliteWalFileBundleURL, to: sqliteWalFileAppSptURL)
}
catch {
    print("Error: \(error)")
}

// compare the copied target files to their source using contentsEqual
let sqliteFileCopied: Bool =
 FileManager.default.contentsEqual(atPath: sqliteFileBundleURL.absoluteString, andPath: sqliteFileAppSptURL.absoluteString)
let sqliteShmFileCopied: Bool =
 FileManager.default.contentsEqual(atPath: sqliteShmFileBundleURL.absoluteString, andPath: sqliteShmFileAppSptURL.absoluteString)
let sqliteWalFileCopied: Bool =
 FileManager.default.contentsEqual(atPath: sqliteWalFileBundleURL.absoluteString, andPath: sqliteWalFileAppSptURL.absoluteString)

Answer 1

啊哈！使用FileManager时，应使用path而不是absoluteString将URL转换为String：

// compare the copied target files to their source using contentsEqual
let sqliteFileCopied: Bool =
 FileManager.default.contentsEqual(atPath: sqliteFileBundleURL.path, andPath: sqliteFileAppSptURL.path)
let sqliteShmFileCopied: Bool =
 FileManager.default.contentsEqual(atPath: sqliteShmFileBundleURL.path, andPath: sqliteShmFileAppSptURL.path)
let sqliteWalFileCopied: Bool =
 FileManager.default.contentsEqual(atPath: sqliteWalFileBundleURL.path, andPath: sqliteWalFileAppSptURL.path)

两者之间的区别在于path生成文件系统类型路径：

/var/folders/kb/y2d_vrl133d1b04_5kc3kw880000gn/T/com.apple.dt.Xcode.pg/resources/238FF955-236A-42FC-B6EA-9A74FC52F235/My_DB.sqlite

而absoluteString生成一个浏览器友好的路径：

file:///var/folders/kb/y2d_vrl133d1b04_5kc3kw880000gn/T/com.apple.dt.Xcode.pg/resources/238FF955-236A-42FC-B6EA-9A74FC52F235/My_DB.sqlite

注意：path也可以在操场上使用别名文件。

比较复制的文件时，FileManager.contentsEqual返回false

1 个答案: