斯威夫特sqlite3的语法和绑定

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 
}

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 
}

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 
}

而且我有一个Book类是这样的：

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 
    } 
}

我是新来的斯威夫特和SQLite。我的问题是：

我是否正确地使用参数绑定？
如何将Data和Date类型绑定到SQLite查询中？（上面代码中的注释行）

任何帮助将不胜感激！

来源

2017-10-20 Jeff

SQLiteError类型来自哪里？ errorMessage定义在哪里？ –

SQLiteError是枚举在同一个文件中定义的。 errorMessage与类中的函数（不是Book类）一起定义。 – Jeff

你问：

我说得对不对与参数绑定做什么呢？

重要。

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，这里定义的：

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

当绑定bookId，要使用sqlite3_bind_int64。
在delete你指的是updatePointer。将其更改为deletePointer。
您应该正在检查这些sqlite3_bind_xxx返回码，并且如果它们不是SQLITE_OK也会发出错误。

你接着问：

如何绑定数据和日期型到SQLite的查询？（在上面的代码中的注释行）

重新日期型，SQLite不具有天然日期类型（见http://sqlite.org/datatype3.html）。或者：

如果你不需要毫秒，使用ISODateFormatter建立一个字符串，并绑定串;
如果您需要毫秒，使用DateFormatter与yyyy-MM-dd'T'HH:mm:ss.SSSXdateFormat，一个locale的Locale(identifier: "en_US_POSIX")，以及TimeZone(secondsFromGMT: 0)一个timeZone，再存储和检索日期为字符串，并将其转换;或
使用timeIntervalSince1970的Date，并将其插入为sqlite3_bind_double。

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很容易使用。 timeIntervalSince1970可以说是更有效一些，但它意味着如果查看第三方SQLite工具中的列，则需要使用unixepoch将double转换为可理解的日期，这可能有点麻烦。这是效率与可用性的平衡。

重新编号Data，插入使用sqlite3_bind_blob。

一对夫妇最终未成年人意见：

你sqlite3_prepare_v2之前，您都推迟sqlite3_finalize。你应该defer吧后sqlite3_prepare_v2。如果准备成功，您应该只是最后确定，而不是失败。
使用WHERE子句进行更新时，可能需要检查sqlite3_changes以查看是否更改了任何记录。对于标识符更新，如果没有更新/删除，我更改了函数以抛出错误。
这些函数中的几个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，使布尔返回值成为冗余）。所以我删除了Bool返回类型。对于其他函数（例如SELECT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Book属性，我删除了book前缀。在SQL中有这个前缀是有意义的（它使得连接查询更容易编写），但是它在Swift类型中是多余的。您通常仅在需要消除歧义时才使用此类前缀（例如，bookDescription，以避免与CustomStringConvertible财产description混淆）。

不管怎么说，拉一起，你喜欢的东西：

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) 
}

有了这些定义：

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 
}

由于斯威夫特3，我更喜欢小写enum值。

来源

2017-10-20 11:39:33 Rob

每个使用Swift的纯SQLite的人都应该阅读https://stackoverflow.com/a/28642293/1187415（现在也正式成为“伟大的答案”） –

感谢Rob！我意识到我错过了一个问题。我如何在SELECT查询中解码它们？特别是当我的数据库有日期和Blob类型。如何将SQLite.Date转换为Swift.Date和SQLite.Blob到Swift.Data中？ – Jeff

如果使用'dateFormatter'将日期转换为字符串，如上所示，当检索它时，可以使用'dateFormatter.date（from：）'将从'sqlite3_column_text'检索到的字符串转换为日期。为了检索'Data'，使用'sqlite3_column_bytes'来获取'Data'的'count'，使用'sqlite3_column_blob'获取'bytes'，并使用'Data（bytes：count）'来构建'Data对象。 – Rob

斯威夫特sqlite3的语法和绑定

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