Swift SQLite3语法和绑定

时间：2017-10-20 10:03:26

标签： swift date sqlite

首先，这些是我的功能：

  1. 插入功能

    func insert(book : Book) throws -> Bool {
    var insertPointer: OpaquePointer? = nil
    let query = "INSERT INTO BOOK (bookName, bookAuthor, bookDesc, bookDate, bookImg, createdBy) VALUES (?, ?, ?, ?, ?, ?)"

    defer{
        sqlite3_finalize(insertPointer)
    }

    if sqlite3_prepare_v2(db, query, -1, &insertPointer, nil) == SQLITE_OK {
        sqlite3_bind_text(insertPointer, 1, book.bookTitle, -1, nil)
        sqlite3_bind_text(insertPointer, 2, book.bookAuthor, -1, nil)
        sqlite3_bind_text(insertPointer, 3, book.bookDesc, -1, nil)
      //sqlite3_bind_date(insertPointer, 4, book.bookDate,nil)
      //sqlite3_bind_image(insertPointer, 5, book.bookImg, -1, nil)
        sqlite3_bind_text(insertPointer, 6, book.createdBy, -1, nil)

        guard sqlite3_step(insertPointer) == SQLITE_DONE else {
            throw SQLiteError.Step(message: errorMessage)
        }
    } else {
        throw SQLiteError.Prepare(message: errorMessage)
    }

    return true
}

  2. 更新功能

    func update(book : Book) throws -> Bool {
    var updatePointer: OpaquePointer? = nil
    var query = "UPDATE Book SET bookName = ?, bookAuthor = ?, bookDesc = ?, bookDate = ?, bookImg = ?, createdBy = ?, WHERE bookId = ?"

    defer{
        sqlite3_finalize(updatePointer)
    }

    if sqlite3_prepare_v2(db, query, -1, &updatePointer, nil) == SQLITE_OK {

        sqlite3_bind_text(updatePointer, 2, book.bookAuthor, -1, nil)
        sqlite3_bind_text(updatePointer, 3, book.bookDesc, -1, nil)
        //sqlite3_bind_date(updatePointer, 4, book.bookDate,nil)
        //sqlite3_bind_image(updatePointer, 5, book.bookImg, -1, nil)
        sqlite3_bind_text(updatePointer, 6, book.createdBy, -1, nil)
        sqlite3_bind_text(updatePointer, 7, book.bookId, -1, nil)
        guard sqlite3_step(updatePointer) == SQLITE_DONE else {
            throw SQLiteError.Step(message: errorMessage)
        }
    } else {
        throw SQLiteError.Prepare(message: errorMessage)
    }

    return true
}

  3. 删除功能

    func delete(book : Book) throws -> Bool {
    var deletePointer: OpaquePointer? = nil
    var query = "DELETE FROM Book WHERE bookId = ?"

    defer{
        sqlite3_finalize(deletePointer)
    }

    if sqlite3_prepare_v2(db, query, -1, &deletePointer, nil) == SQLITE_OK {
        sqlite3_bind_text(updatePointer, 1, book.bookId, -1, nil)
        guard sqlite3_step(deletePointer) == SQLITE_DONE else {
            throw SQLiteError.Step(message: errorMessage)
        }
    } else {
        throw SQLiteError.Prepare(message: errorMessage)
    }

    return true
}

    4. 我有一个Book这样的课程：

    class Book{
    var bookId : Int
    var bookImg : Data
    var bookTitle : String
    var bookAuthor : String
    var bookDesc : String
    var bookDate : Date
    var createdBy : String

    init(bookId : Int, bookImg : Data, bookTitle : String, bookAuthor : String, bookDesc : String, bookDate : Date, createdBy : String){
        self.bookId = bookId
        self.bookImg = bookImg
        self.bookTitle = bookTitle
        self.bookAuthor = bookAuthor
        self.bookDesc = bookDesc
        self.bookDate = bookDate
        self.createdBy = createdBy
    }
}

    我是Swift和SQLite的新手。我的问题是：

    1. 我是否正确使用参数绑定？

    2. 如何将Data和Date类型绑定到SQLite查询中？ （上面代码中的注释行）

      3. 非常感谢任何帮助！

1 个答案:

答案 0 :(得分：7)

你问：

  
      
  1. 我是否正确使用参数绑定？
    2.   

很大程度上。

  • 绑定字符串时，谨慎使用SQLITE_TRANSIENT作为sqlite3_bind_text和sqlite3_bind_blob的最后一个参数，如下所示：

    internal let SQLITE_STATIC = unsafeBitCast(0, to: sqlite3_destructor_type.self)
internal let SQLITE_TRANSIENT = unsafeBitCast(-1, to: sqlite3_destructor_type.self)

  • 绑定bookId时，您要使用sqlite3_bind_int64。

  • delete updatePointer您指的是deletePointer。将其更改为sqlite3_bind_xxx。

  • 您可能应该检查这些SQLITE_OK返回代码并在他们不是ISODateFormatter的情况下抛出错误。

然后你问：

  
      
  1. 如何将数据和日期类型绑定到SQLite查询中？ （上面代码中的注释行）
    2.   

重新日期类型，SQLite没有本机日期类型（请参阅http://sqlite.org/datatype3.html）。之一：

  • 如果您不需要毫秒，请使用DateFormatter构建字符串，并绑定字符串;
  • 如果您需要毫秒，请使用dateFormat yyyy-MM-dd'T'HH:mm:ss.SSSX locale，Locale(identifier: "en_US_POSIX") timeZone和TimeZone(secondsFromGMT: 0) {{} 1}}，再次将日期存储和检索为字符串并进行转换;或
  • 使用timeIntervalSince1970的{​​{1}}，并将其插入Date。

以前的字符串替换方法最容易使用，并且在第三方工具中直观地检查数据库时非常容易。 sqlite3_bind_double可以说有点效率，但它只是意味着如果查看第三方SQLite工具中的列，您需要使用timeIntervalSince1970将双精度转换为可理解的日期，这可能是一点点繁琐。这是效率与可用性之间的权衡。

重新unixepoch，使用Data插入。

最后一些小的意见：

  • 您要在sqlite3_bind_blob之前推迟sqlite3_finalize。您应该在 sqlite3_prepare_v2之后defer 。如果准备成功，您应该只是最终确定，而不是在失败时。

  • 在使用sqlite3_prepare_v2子句进行更新时，您可能需要检查WHERE以查看是否有任何记录更改。对于标识符的更新，如果没有更新/删除任何内容，我将函数更改为抛出错误。

  • 其中一些函数被定义为抛出错误以及返回布尔值。对于没有意义的更新/删除函数（因为我们使用错误来知道它是否成功，使布尔返回值变为冗余）。所以我删除了sqlite3_changes返回类型。对于其他函数（例如Bool例程），返回值显然有意义，但不适用于这些通过/失败更新例程。

  • 对于SELECT属性，我删除了Book前缀。在SQL中使用该前缀是有意义的（它使连接查询更容易编写），但在Swift类型中它是多余的。您通常只使用消除歧义所需的那种前缀（例如book，以避免与bookDescription属性混淆，CustomStringConvertible）。

无论如何，将它们拉在一起，就会得到类似的东西：

description

有了这些定义：

var dateFormatter: DateFormatter = {
    let _formatter = DateFormatter()
    _formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSX"
    _formatter.locale = Locale(identifier: "en_US_POSIX")
    _formatter.timeZone = TimeZone(secondsFromGMT: 0)
    return _formatter
}()

var errorMessage: String { return String(cString: sqlite3_errmsg(db)) }

func insert(book: Book) throws {
    var statement: OpaquePointer? = nil
    let query = "INSERT INTO book (bookName, bookAuthor, bookDesc, bookDate, bookImg, createdBy) VALUES (?, ?, ?, ?, ?, ?)"

    guard sqlite3_prepare_v2(db, query, -1, &statement, nil) == SQLITE_OK else {
        throw SQLiteError.prepare(message: errorMessage)
    }

    defer { sqlite3_finalize(statement) }

    guard sqlite3_bind_text(statement, 1, book.title, -1, SQLITE_TRANSIENT) == SQLITE_OK else {
        throw SQLiteError.bind(message: errorMessage)
    }

    guard sqlite3_bind_text(statement, 2, book.author, -1, SQLITE_TRANSIENT) == SQLITE_OK else {
        throw SQLiteError.bind(message: errorMessage)
    }

    guard sqlite3_bind_text(statement, 3, book.bookDescription, -1, SQLITE_TRANSIENT) == SQLITE_OK else {
        throw SQLiteError.bind(message: errorMessage)
    }

    guard sqlite3_bind_text(statement, 4, dateFormatter.string(from: book.createDate), -1, SQLITE_TRANSIENT) == SQLITE_OK else {
        throw SQLiteError.bind(message: errorMessage)
    }

    guard book.image.withUnsafeBytes({ (bytes: UnsafePointer<UInt8>) -> Int32 in
        sqlite3_bind_blob(statement, 5, bytes, Int32(book.image.count), SQLITE_TRANSIENT)
    }) == SQLITE_OK else {
        throw SQLiteError.bind(message: errorMessage)
    }

    guard sqlite3_bind_text(statement, 6, book.createdBy, -1, SQLITE_TRANSIENT) == SQLITE_OK else {
        throw SQLiteError.bind(message: errorMessage)
    }

    guard sqlite3_step(statement) == SQLITE_DONE else {
        throw SQLiteError.step(message: errorMessage)
    }
}

func update(book: Book) throws {
    var statement: OpaquePointer? = nil
    let query = "UPDATE Book SET bookName = ?, bookAuthor = ?, bookDesc = ?, bookDate = ?, bookImg = ?, createdBy = ?, WHERE bookId = ?"

    guard sqlite3_prepare_v2(db, query, -1, &statement, nil) == SQLITE_OK else {
        throw SQLiteError.prepare(message: errorMessage)
    }

    defer { sqlite3_finalize(statement) }

    guard sqlite3_bind_text(statement, 2, book.author, -1, SQLITE_TRANSIENT) == SQLITE_OK else {
        throw SQLiteError.bind(message: errorMessage)
    }

    guard sqlite3_bind_text(statement, 3, book.bookDescription, -1, SQLITE_TRANSIENT) == SQLITE_OK else {
        throw SQLiteError.bind(message: errorMessage)
    }

    guard sqlite3_bind_text(statement, 4, dateFormatter.string(from: book.createDate), -1, SQLITE_TRANSIENT) == SQLITE_OK else {
        throw SQLiteError.bind(message: errorMessage)
    }

    guard book.image.withUnsafeBytes({ (bytes: UnsafePointer<UInt8>) -> Int32 in
        sqlite3_bind_blob(statement, 5, bytes, Int32(book.image.count), SQLITE_TRANSIENT)
    }) == SQLITE_OK else {
        throw SQLiteError.bind(message: errorMessage)
    }

    guard sqlite3_bind_text(statement, 6, book.createdBy, -1, SQLITE_TRANSIENT) == SQLITE_OK else {
        throw SQLiteError.bind(message: errorMessage)
    }

    guard sqlite3_bind_int64(statement, 7, Int64(book.id)) == SQLITE_OK else {
        throw SQLiteError.bind(message: errorMessage)
    }

    guard sqlite3_step(statement) == SQLITE_DONE else {
        throw SQLiteError.step(message: errorMessage)
    }

    guard sqlite3_changes(db) > 0 else {
        throw SQLiteError.noDataChanged
    }
}

func delete(book: Book) throws {
    var statement: OpaquePointer? = nil
    let query = "DELETE FROM Book WHERE bookId = ?"

    guard sqlite3_prepare_v2(db, query, -1, &statement, nil) == SQLITE_OK else {
        throw SQLiteError.prepare(message: errorMessage)
    }

    defer { sqlite3_finalize(statement) }

    guard sqlite3_bind_int64(statement, 1, Int64(book.id)) == SQLITE_OK else {
        throw SQLiteError.bind(message: errorMessage)
    }

    guard sqlite3_step(statement) == SQLITE_DONE else {
        throw SQLiteError.step(message: errorMessage)
    }

    guard sqlite3_changes(db) > 0 else {
        throw SQLiteError.noDataChanged
    }
}

func select(bookId: Int) throws -> Book {
    var statement: OpaquePointer? = nil
    let query = "SELECT bookId, bookName, bookAuthor, bookDesc, bookDate, bookImg, createdBy FROM Book WHERE bookId = ?"

    guard sqlite3_prepare_v2(db, query, -1, &statement, nil) == SQLITE_OK else {
        throw SQLiteError.prepare(message: errorMessage)
    }

    defer { sqlite3_finalize(statement) }

    guard sqlite3_bind_int64(statement, 1, Int64(bookId)) == SQLITE_OK else {
        throw SQLiteError.bind(message: errorMessage)
    }

    guard sqlite3_step(statement) == SQLITE_ROW else {
        throw SQLiteError.step(message: errorMessage)
    }

    return try book(for: statement)
}

func selectAll() throws -> [Book] {
    var statement: OpaquePointer? = nil
    let query = "SELECT bookId, bookName, bookAuthor, bookDesc, bookDate, bookImg, createdBy FROM Book"

    guard sqlite3_prepare_v2(db, query, -1, &statement, nil) == SQLITE_OK else {
        throw SQLiteError.prepare(message: errorMessage)
    }

    defer { sqlite3_finalize(statement) }

    var books = [Book]()

    var rc: Int32
    repeat {
        rc = sqlite3_step(statement)
        guard rc == SQLITE_ROW else { break }
        books.append(try book(for: statement))
    } while rc == SQLITE_ROW

    guard rc == SQLITE_DONE else {
        throw SQLiteError.step(message: errorMessage)
    }

    return books
}

func book(for statement: OpaquePointer?) throws -> Book {
    let bookId = Int(sqlite3_column_int64(statement, 0))

    guard let bookNameCString = sqlite3_column_text(statement, 1) else {
        throw SQLiteError.column(message: errorMessage)
    }
    let bookName = String(cString: bookNameCString)

    guard let bookAuthorCString = sqlite3_column_text(statement, 2) else {
        throw SQLiteError.column(message: errorMessage)
    }
    let bookAuthor = String(cString: bookAuthorCString)

    guard let bookDescCString = sqlite3_column_text(statement, 3) else {
        throw SQLiteError.column(message: errorMessage)
    }
    let bookDesc = String(cString: bookDescCString)

    guard let bookDateCString = sqlite3_column_text(statement, 4) else {
        throw SQLiteError.column(message: errorMessage)
    }
    guard let bookDate = dateFormatter.date(from: String(cString: bookDateCString)) else {
        throw SQLiteError.invalidDate
    }

    let bookImgCount = Int(sqlite3_column_bytes(statement, 5))
    guard bookImgCount > 0 else {
        throw SQLiteError.missingData
    }
    guard let bookImgBlog = sqlite3_column_blob(statement, 5) else {
        throw SQLiteError.column(message: errorMessage)
    }
    let bookImg = Data(bytes: bookImgBlog, count: bookImgCount)

    guard let createdByCString = sqlite3_column_text(statement, 6) else {
        throw SQLiteError.column(message: errorMessage)
    }
    let createdBy = String(cString: createdByCString)

    return Book(id: bookId, image: bookImg, title: bookName, author: bookAuthor, bookDescription: bookDesc, createDate: bookDate, createdBy: createdBy)
}

虽然我相信您应该检查所有struct Book { var id: Int var image: Data var title: String var author: String var bookDescription: String // this is the only one where I kept the `book` prefix, simply because `description` is a reserved name var createDate: Date var createdBy: String } enum SQLiteError: Error { case open(result: Int32) case exec(message: String) case prepare(message: String) case bind(message: String) case step(message: String) case column(message: String) case invalidDate case missingData case noDataChanged } 次错误调用，但我个人觉得上述所有内容都有点难看。我建议包装所有SQLite3调用，让你摆脱杂草。那里有很多。 This a thin wrapper将上述代码简化为：

sqlite3_xxx
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