ios - 无法打开文件，因为在尝试打开 SQLite3 数据库时无法确定其内容的文本编码

Question

我正在使用 FMDB 库通过以下代码在我的 iOS 应用程序中打开 sqlite 3 数据库文件。

    //
//  DatabaseLoader.swift
//  Museum-App-iOS
//
//  Created by THOMAS NEEDHAM on 12/07/2015.
//  Copyright (c) 2015 THOMAS NEEDHAM. All rights reserved.
//
//  This class uses the FMDB libary from https://github.com/ccgus/fmdb 
//  Which is licenced under the MIT Licence
//  Copyright (c) 2008-2014 Flying Meat Inc.

import Foundation
import UIKit

internal class DatabaseLoader: NSObject {

var resourcesFolder:NSURL
var path:String
var database:FMDatabase!

internal override init(){
    //resourcesFolder = NSSearchPathForDirectoriesInDomains(NSSearchPathDirectory.DocumentDirectory, NSSearchPathDomainMask.UserDomainMask, true)[0] as! String
    do{
            self.resourcesFolder = NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource("museumDB", ofType: "")!)
            self.path = try String(contentsOfURL: self.resourcesFolder)
            self.database = FMDatabase(path: self.path)
    }
    catch let error as NSError{
        NSLog("%@", error.description)
        self.path = "ERROR"
        self.database = nil
    }
    super.init()
}

internal func openDatabase() -> Bool{
    // try to open the database
    if(!database.open()){
        NSLog("Database Not Opened")
        return false
    }
    else{
        NSLog("Database Opened Successfully YAY")
        //NSLog("DB Path %@", self.getDatabasePath())
        return true
    }

}

internal func closeDatabase() -> Bool{
    // try to close the database
    if(!database.close()){
        NSLog("Database Not Closed")
        return false
    }
    else{
        NSLog("Database Closed Successfully YAY")
        return true
    }
}

internal func queryDatabase(query: String) -> FMResultSet!{
    // try to open the database
    if(!openDatabase()){
        NSLog("Database could not be opened for queries")
        return nil
    }
    else{
        NSLog("Database opened for queries")
        // try to begin a transaction with the database
        if(!database.beginTransaction()){
            NSLog("Could not begin a database transaction")
            return nil
        }
        else{
            // try to query the database
            NSLog("Database transaction started succesfully")
            let results = database.executeQuery(query)
            if(results == nil){
            NSLog("Query Failed")
                return nil
            }
            else{
                // if the query was successful return the results
                NSLog("Query Successful")
                return results
            }
        }
    }
}

internal func getDatabasePath() -> NSString{
    return database.databasePath()!
}

func copyDatabase(){
    let storePath : NSString = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true).last! // get the location of the documents directory
    let fileManager : NSFileManager = NSFileManager.defaultManager() // get the file manager
    var fileCopyError:NSError? = NSError(domain: "Local", code: 0, userInfo: nil) // create an error pointer
    if !fileManager.fileExistsAtPath((storePath as String) + "/museumDB" as String) { // check if the database already exists
        NSLog("Copying Database")
        let defaultStorePath : NSString! = NSBundle.mainBundle().pathForResource("museumDB", ofType: "") // get the default location of the database when the app was first installed
        if((defaultStorePath) != nil) { // if the database exists within the original location
            do {
                try fileManager.copyItemAtPath(defaultStorePath as String, toPath: storePath as String)
            } catch let error as NSError {
                fileCopyError = error
            } // copy it to the documents folder
        }
    }
    else{
        NSLog("Database Already Exists")
    }

}
}

上述代码在本周早些时候的 swift 2 更新之前运行良好。现在代码崩溃并给出以下错误。

Error Domain=NSCocoaErrorDomain Code=264 "The file “museumDB” couldn’t be opened because the text encoding of its contents can’t be determined." UserInfo={NSFilePath=/Users/thomasneedham/Library/Developer/CoreSimulator/Devices/B60A965A-26C7-44C2-9643-0928BD6A2BBF/data/Containers/Bundle/Application/70DADB9D-0027-4B8A-8FB8-7DF47B0963DB/Museum-App-iOS.app/museumDB}

我尝试使用谷歌搜索，但没有找到任何可以帮助我解决问题的方法。我对 iOS 相当陌生，所以如果你也能向我解释问题是什么以及你的解决方案如何解决问题，那将对我扩展我的知识非常有帮助。

提前致谢

Answer 1

此代码正在获取包中 museumDB 的路径，将其转换为 NSURL，将 URL 引用的文件内容加载到 String 变量，然后显然假设那些 String 内容引用数据库实际所在的 path。这无疑不是您想要的。

如果 museumDB 是实际的数据库，通常您只需直接打开数据库:

internal override init(){
    path = NSBundle.mainBundle().pathForResource("museumDB", ofType: "")!)
    database = FMDatabase(path: path)

    super.init()
}

或者，您通常会查看数据库是否存在于 Documents 文件夹中，如果不存在，则将其从 bundle 复制到 Documents 文件夹，然后只需在 Documents 中打开该数据库。 (例如，我注意到您有一个 copyDatabase 方法正在尝试执行类似的操作，但您从未调用过它，也从未在 Documents 中打开过这个新副本。)例如你可以这样做:

func openDatabase() -> Bool {
    let fileManager = NSFileManager.defaultManager() // get the file manager
    let documentsFolder = try! fileManager.URLForDirectory(.DocumentDirectory, inDomain: .UserDomainMask, appropriateForURL: nil, create: false)
    let documentURL = documentsFolder.URLByAppendingPathComponent("museumDB")
    let bundleURL = NSBundle.mainBundle().URLForResource("museumDB", withExtension: nil)!

    var error: NSError?
    if !documentURL.checkResourceIsReachableAndReturnError(&error) {
        do {
            try fileManager.copyItemAtURL(bundleURL, toURL: documentURL)
        } catch let error as NSError {
            NSLog("%@", error.localizedDescription)
            return false
        }
    }

    database = FMDatabase(path: documentURL.path)
    return database.open()
}

这显然假设数据库名为 museumDB。就个人而言，我会使用像 museum.db 或 museum.sqlite 这样的名称，但这是个人喜好的问题。