那些遇到过的问题

Swift SQLite3语法和绑定

Jef*_*eff 4 sqlite date swift

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
}
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  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
}
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  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
}
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我有一个Book这样的课:

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
    }
}
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我是Swift和SQLite的新手.我的问题是:

  1. 我用参数绑定做得对吗？

  2. 如何绑定Data并Date输入SQLite查询？(上面代码中的注释行)

任何帮助将不胜感激!

Rob*_*Rob 10

您询问:

  1. 我用参数绑定做得对吗？

大部分.

  • 当绑定字符串,它可能是谨慎使用SQLITE_TRANSIENT作为最后一个参数来sqlite3_bind_text和sqlite3_bind_blob,这里定义:

    internal let SQLITE_STATIC = unsafeBitCast(0, to: sqlite3_destructor_type.self)
internal let SQLITE_TRANSIENT = unsafeBitCast(-1, to: sqlite3_destructor_type.self)
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  • 绑定时bookId,您想要使用sqlite3_bind_int64.

  • 在delete你指的是updatePointer.改为deletePointer.

  • 您可能应该检查这些sqlite3_bind_xxx返回代码并抛出错误,如果它们也不SQLITE_OK是.

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)

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

  • 如果您不需要毫秒,请使用ISODateFormatter构建字符串并绑定字符串;
  • 如果您需要毫秒,使用withFractionalSeconds带DateFormatter的dateFormat,一yyyy-MM-dd'T'HH:mm:ss.SSSX中locale和Locale(identifier: "en_US_POSIX")的timeZone,并再次存储和检索日期为字符串,并将其转换; 要么
  • 使用TimeZone(secondsFromGMT: 0)的timeIntervalSince1970,并插入的Date.

以前的字符串替代方法最容易使用,并且在第三方工具中直观地检查数据库时非常容易.该sqlite3_bind_double可以说是一点点更有效,但它只是意味着你需要使用timeIntervalSince1970到双转换成易懂的日期是否在寻找第三方的SQLite工具之列,这可有点繁琐.这是效率与可用性之间的权衡.

重新unixepoch插入,使用Data.

几个最后的小观察:

  • 你在推卸sqlite3_bind_blob你之前sqlite3_finalize.你应该sqlite3_prepare_v2它之后 defer.如果准备成功,您应该只是最终确定,而不是如果失败.

  • 在使用sqlite3_prepare_v2子句进行更新时,您可能需要检查WHERE是否有任何记录已更改.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,避免与bookDescription财产混淆CustomStringConvertible).

无论如何,把它拉到一起,你会得到类似的东西:

let formatter = ISO8601DateFormatter()
formatter.formatOptions.insert(.withFractionalSeconds)
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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: inout 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({ bufferPointer -> Int32 in
        sqlite3_bind_blob(statement, 5, bufferPointer.baseAddress, 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)
    }

    book.id = Int(sqlite3_last_insert_rowid(db))
}

func update(_ book: Book) throws {
    guard let id = book.id.flatMap({ Int64($0) }) else {
        throw SQLiteError.noDataChanged
    }

    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, 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({ bufferPointer -> Int32 in
        sqlite3_bind_blob(statement, 5, bufferPointer.baseAddress, 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, 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 {
    guard let id = book.id.flatMap({ Int64($0) }) else {
        throw SQLiteError.noDataChanged
    }

    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, 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)
}
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从Swift 3开始,我更喜欢小写description值.

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