Question

我试图将FMDB SQLite查询的结果附加到Swift数组。我在XCode中遇到的错误是选项类型的值＆＃39;字符串？＆＃39;没有打开。＆＃39;

在while循环中交换下面的行，FMDB结果可以打印到控制台OK，所以没有问题。

println(results_lab_test?.stringForColumn("lab_test"))

XCode新手，所以要善待......

  import UIKit

class ViewController: UIViewController {


    @IBOutlet weak var tests_label: UILabel!

    var databasePath = NSString()

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view, typically from a nib.

        var arrayData:[String] = []



        let filemgr = NSFileManager.defaultManager()

        let dirPaths = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)

        let docsDir = dirPaths[0] as! String

        databasePath = docsDir.stringByAppendingPathComponent("vmd_db.db")

        let myDatabase = FMDatabase(path: databasePath as String)

        if myDatabase.open(){

            let query_lab_test = "SELECT lab_test FROM lab_test"

            let results_lab_test:FMResultSet? = myDatabase.executeQuery(query_lab_test, withArgumentsInArray: nil)

            while results_lab_test?.next() == true {
                if let resultString = results_lab_test?.stringForColumn("lab_test"){
                arrayData.append(resultString)
                    var multiLineString = join("\n", arrayData)
                    tests_label.text = multiLineString
                    tests_label.numberOfLines = 0
                    tests_label.lineBreakMode = NSLineBreakMode.ByWordWrapping
                    tests_label.sizeToFit()

            }

        }
    }
    }


    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}

工作代码归功于@skypecakes：

import UIKit

class ViewController: UIViewController {


    @IBOutlet weak var tests_label: UILabel!

    var databasePath = NSString()

    override func viewDidLoad() {
        super.viewDidLoad()

        let filemgr = NSFileManager.defaultManager()

        let dirPaths = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)

        let docsDir = dirPaths[0] as! String

        databasePath = docsDir.stringByAppendingPathComponent("vmd_db.db")

        let myDatabase = FMDatabase(path: databasePath as String)

        if myDatabase.open(){

            var arrayData:[String] = []

            let query_lab_test = "SELECT lab_test FROM lab_test"

            let results_lab_test:FMResultSet? = myDatabase.executeQuery(query_lab_test, withArgumentsInArray: nil)

            while results_lab_test?.next() == true {

                if let resultString = results_lab_test?.stringForColumn("lab_test"){

                arrayData.append(resultString)

            }
        }
            println(arrayData)
            myDatabase.close()
    }
    }


    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}

Answer 1

好像是 results_lab_test?.stringForColumn("lab_test") 返回一个String？，这是一个可选的。您的数组被定义为“String”项的数组，因此您不能放置“String？”在里面。试试这个：

if let resultString = results_lab_test?.stringForColumn("lab_test")
    arrayData.append(resultString)

请注意，一般情况下，最好使用“if let”展开所有选项，而不是假设它们已填充。所以无论你有问号（例如results_lab_test？.stringForColumn），都可以使用“if let”。

如果您正在使用带有Swift 2.0的XCode 7，这对于“guard let”语句来说是一个很好的例子，如果可选的返回null，它提供了一个方便的语法来中止代码：

guard let queryResults = results_lab_test else return
while queryResults.next() == true {
if let resultString = queryResults.stringForColumn("lab_test")
        arrayData.append(resultString)
}

此测试适用于我（表格有2行，打印数组打印2行），以防它帮助您：

import UIKit
import FMDB

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

        if let myDatabase = makeSqlDB()
        {
            var arrayData:[String] = []
            let query_lab_test = "SELECT lab_test FROM lab_test"

            let results_lab_test:FMResultSet? = myDatabase.executeQuery(query_lab_test, withArgumentsInArray: nil)

            while results_lab_test?.next() == true
            {
                if let resultString = results_lab_test?.stringForColumn("lab_test")
                {
                    arrayData.append(resultString)
                }
            }

            println(arrayData)
            myDatabase.close()
        }
    }


    private func makeSqlDB()->FMDatabase?
    {
        let database = FMDatabase(path: String())

        if !database.open() {
            println("Unable to open database")
            return nil
        }

        if !database.executeUpdate("create table lab_test(lab_test text)", withArgumentsInArray: nil) {
            println("create table failed: \(database.lastErrorMessage())")
        }

        if !database.executeUpdate("insert into lab_test (lab_test) values (?)", withArgumentsInArray: ["test1"]) {
            println("insert 1 table failed: \(database.lastErrorMessage())")
        }

        if !database.executeUpdate("insert into lab_test (lab_test) values (?)", withArgumentsInArray: ["test2"]) {
            println("insert 2 table failed: \(database.lastErrorMessage())")
        }

        return database
    }


    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}

将FMDB SQLite结果附加到Swift数组

1 个答案: