Question

我正在使用SQLite.swift，我正在使用SQLite.swift演示中的这些代码。

import UIKit
import SQLite

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        let db = try! Connection()
        let users = Table("users")
        let id = Expression<Int64>("id")
        let email = Expression<String>("email")
        let name = Expression<String?>("name")
        try! db.run(users.create { t in
            t.column(id, primaryKey: true)
            t.column(email, unique: true, check: email.like("%@%"))
            t.column(name)
        })
        try! db.run(users.insert(email <- "alice@mac.com"))
        for user in db.prepare(users) {
            print("id: \(user[id]), email: \(user[email])")
        }
    }
}

我第一次运行它时，输出是：

("SELECT * FROM \"users\"", [])
id: 1, email: alice@mac.com

然后我删除了第17行（try! db.run(users.insert(email <- "alice@mac.com"))）并再次运行，调试器输出更改为：

("SELECT * FROM \"users\"", [])

看起来alice@mac.com没有保存到数据库。那么我做错了什么？或者如何将其保存到SQLite数据库中？

P.S。我正在使用Xcode 7 beta 5，Swift 2.0

Answer 1

let db = try! Connection()

创建一个内存中数据库，您可以从API文档中看到：

/// Initializes a new SQLite connection.
///
/// - Parameters:
///
///   - location: The location of the database. Creates a new database if it
///     doesn’t already exist (unless in read-only mode).
///
///     Default: `.InMemory`.
///
///   - readonly: Whether or not to open the database in a read-only state.
///
///     Default: `false`.
///
/// - Returns: A new database connection.
public init(_ location: Location = .InMemory, readonly: Bool = false) throws

数据不会持久保存到文件中，并且数据库始终是最初的空。

对于持久性数据库，请使用

/// Initializes a new connection to a database.
///
/// - Parameters:
///
///   - filename: The location of the database. Creates a new database if
///     it doesn’t already exist (unless in read-only mode).
///
///   - readonly: Whether or not to open the database in a read-only state.
///
///     Default: `false`.
///
/// - Throws: `Result.Error` iff a connection cannot be established.
///
/// - Returns: A new database connection.
public convenience init(_ filename: String, readonly: Bool = false) throws

而是，例如

// Compute file path for database in Documents directory:
let docsDir = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true).last!
let dbPath = (docsDir as NSString).stringByAppendingPathComponent("database.sqlite")

do {
    let db = try Connection(dbPath)
    // ... use database

} catch (error) {
    // Could not create or open database, print error
}

Answer 2

viewDidLoad首先创建表，然后插入。

当表已经存在时，我不知道表create function的行为，但是如果它没有给你带来任何错误，它可能会再次重新创建表。如果是这种情况，在调用插入注释掉的viewDidLoad之后，您可能最终得到一个全新的空白表。

尝试更改逻辑，确保每次都不重新创建表。

Answer 3

你可以拥有这样的东西（显然其他人都可以改进代码）：

创建表格模型：

class TUsers {
static let TABLE_NAME : String = “users”
static let ID = Expression<Int64>("id")
static let EMAIL = Expression<String>(“email”)
static let NAME = Expression<String>(“name”)

class func addUser(email : String!, name : String!) -> Bool{

    let users = Table(TABLE_NAME)

    do {

        try DBHelper.instance.db.run(users.insert(
            TUsers.EMAIL <- email,
            TUsers.NAME <- name
        ))

        return true
    } catch {
        print("Insert failed")
        return false
    }
}

class func getAllUsers() -> [User] { // you must create the model user
    let users = Table(TUsers.TABLE_NAME)

    let query = users.select(*)
        //.filter(TUsers.EMAIL == “whatever@pomberobota.com”)

    var listOfUsers : [Users] = []

    for user in DBHelper.instance.db.prepare(query) {
        // Do whatever you need to instantiate the model User


        listOfUsers.append(User(email: users[TUsers.EMAIL], name: users[TUsers.NAME])

    }

    return listOfUsers
}
}

创建数据库助手

class DBHelper {

static let instance = DBHelper()

var db : Connection

init() {
    do {
        self.db = try Connection("\(Util.getDBPath())/db.sqlite3")
        createTablesIfNotExists()
    } catch {
        print("Could not create a connection to database")
    }
}

func createTablesIfNotExists() {

    let users = Table(TUsers.TABLE_NAME)
    do {
        try db.run(logs.create(ifNotExists: true) { t in
                t.column(TUsers.ID, primaryKey: true)
                t.column(TUsers.EMAIL)
                t.column(TUsers.NAME)
        })
    } catch {
        print(“Could not create table users”)
    }
}
}

最后（这里你不需要导入SQLite）。

class ViewController: UIViewController {
override func viewDidLoad() {
    super.viewDidLoad()

   TUsers.addUser(“user@ndetavysho.com”, “John Capuchon”)

    let users = TUsers.getAllUsers()

    for user in users {
        // do something
    }
}

}

为什么将数据保存到SQLite数据库不适用于Swift 2？

3 个答案: