例如

      var FMDBQueue = FMDatabaseQueue(path:"db path")

      FMDBQueue.inTransaction{ (db, rollback) in
        do
        {
            let resultset = try db.executeQuery(queryString, values: [])
            while(resultset.next()){
                //do your task

             }

        }
        catch
        {
            rollback.memory = true
            print(error)
        }

    }

Answer 2

FMDatabaseQueue序列化所有数据库访问。您无法与FMDatabaseQueue同时执行多个读取操作，并且永远不会：这不是FMDatabaseQueue的目的。

不幸的是，FMDB没有提供任何其他安全的并发模型。您可以使用原始FMDatabase连接，并处理写序列化和并行读取。例如，您可以将数据库调用包装在并发DispatchQueue中：

import "gitlab.com/kokizzu/gokil/I"
import "sync/atomic"

var CACHE_IDX int64
var CACHE_KEYS cmap.CMap

func init() {
    CACHE_KEYS = cmap.New()
}

// change a really long string to a shorter one 
func RamKey_ByQuery(query string) string {
    nkey := CACHE_KEYS.Get(query)
    if nkey != nil {
        return nkey.(string)
    }
    new_idx := atomic.AddInt64(&CACHE_IDX, 1)
    ram_key := `:` + I.ToS(new_idx) // convert integer to string
    CACHE_KEYS.Set(query, ram_key)
    return ram_key
}

此解决方案有一些警告：并发读取的数量不受限制，您不会从事务或保存点周围的DatabaseQueue高级API中获利，let dbQueue = DispatchQueue(label: "database", attributes: .concurrent) func read(block: () -> ()) { // Since the queue is concurrent, several readers can execute at // the same time. dbQueue.sync(execute: block) } func write(block: () -> ()) { // The barrier flag makes sure that only one writer block is executing // at a given time, and that no reader is currently executing. dbQueue.sync(flags: .barrier, execute: block) } let db = FMDatabase(...) read { // Select from db } write { // Write in db }方法不会阻止您执行数据库更新。

您可以检查FMDB的替代方案：GRDB.swift库。它与FMDB非常相似。但是，与FMDB不同，它提供了一个DatabasePool类，可以避免上面列出的所有警告：https://github.com/groue/GRDB.swift#database-pools

read

Answer 3

检查此链接对您有用：

http://www.theappguruz.com/blog/use-sqlite-database-swift

获取数据：

@IBAction func findContact（_ sender：AnyObject）{ let contactDB = FMDatabase（path：databasePath as String）

if (contactDB?.open())! {
    let querySQL = "SELECT address, phone FROM CONTACTS WHERE name = '\(name.text!)'"

    let results:FMResultSet? = contactDB?.executeQuery(querySQL,
                                           withArgumentsIn: nil)

    if results?.next() == true {
        address.text = results?.string(forColumn: "address")
        phone.text = results?.string(forColumn: "phone")
        status.text = "Record Found"
    } else {
        status.text = "Record not found"
        address.text = ""
        phone.text = ""
    }
    contactDB?.close()
} else {
    print("Error: \(contactDB?.lastErrorMessage())")
}

}

使用多线程读取FMDB数据库

3 个答案:

例如