Question

我们正在使用Swift在iOS中实现SQLite，而不使用包装器或Objective-C桥接。一切正常，除了在进行查询和提取结果时。问题在于，在Swift中从SQLite返回的UnsafePointer<UInt8>如下：

var querySQL = "SELECT address, phone FROM CONTACTS WHERE NAME = 'myName'"
var cQuery = querySQL.cStringUsingEncoding(NSUTF8StringEncoding)
var statement: COpaquePointer = nil
if sqlite3_prepare_v2(contactsDB, cQuery!, -1, &statement, nil) == SQLITE_OK {
   if sqlite3_step(statement) == SQLITE_ROW {
   var address : UnsafePointer<UInt8> = sqlite3_column_text(statement, 0)
   var data = NSData(bytes: address, length: 10)
   var string = NSString(data: data, encoding: NSUTF8StringEncoding)
   println(string)

如您所见，如果我们知道对象的长度（在本例中为10），我们可以将指针转换为String

要深入研究这个问题，我有以下示例

let pointerFromString: UnsafePointer<Int8> = "xyz".cStringUsingEncoding(NSUTF8StringEncoding)
let stringFromPointer = String.fromCString(anotherPointerFromString_Int8)                    println(stringFromPointer!)

鉴于CChar是Int8的别名，我可以使用String将UnsafePointer<Int8>转换为.cStringUsingEncoding()，然后返回String使用.fromCString(<UnsafePointer_CChar>)

问题是我的SQLite结果是UnsafePointer_UInt8，无法与.fromCString()一起使用

最重要的问题是：是否可以将UnsafePointer_UInt8转换为UnsafePointer_Int8

Answer 1

这应该有效：

let address = sqlite3_column_text(statement, 0)
let string = String.fromCString(UnsafePointer<CChar>(address))

更新Swift 3（Xcode 8），比较Swift 3: convert a null-terminated UnsafePointer<UInt8> to a string：

let string = String(cString: sqlite3_column_text(statement, 0))

Swift中的SQLite项目中的UnsafePointer <uint8>问题</uint8>

1 个答案: