如何在 SQLite.swift 中升级数据库版本并在表中添加新列

Question

如何升级 SQLite.swift 中的数据库版本并使用https://github.com/stephencelis/SQLite.swift/blob/master/Documentation/Index.md在 swift 中的表中添加新列

//migration of db version


    extension Connection {
        public var userVersion: Int32 {
            get { return Int32(try! scalar("PRAGMA user_version") as! Int64)}
            set { try! run("PRAGMA user_version = \(newValue)") }
        }
    }
    //in viewdidLoad of viewcontroller
    if db.userVersion == 0 {
        // handle first migration
        db.userVersion = 1
    }
    if db.userVersion == 1 {
        // handle second migration
        db.userVersion = 2
    }
    //my table and want to upgrade with some new columns 
    do 
    {
    let offlineLocationTable = sqliteOfflineLocationTable.offlineLocationTable.create(ifNotExists: true) { (table) in
    table.column(sqliteOfflineLocationTable.id, primaryKey: true)
    table.column(sqliteOfflineLocationTable.status)
    table.column(sqliteOfflineLocationTable.loadid)
    table.column(sqliteOfflineLocationTable.jobid)
    table.column(sqliteOfflineLocationTable.lat)
    table.column(sqliteOfflineLocationTable.lng)
    // this is new columns which i want to add in new version of db
    table.column(sqliteOfflineLocationTable.t)
     print("offline location table created")
     }
      try self.db.run(offlineLocationTable)    
     } catch {
    print(error)
    }

 // this code run successfully but when i try to get the column value it carsh due to No such column "t" in columns [........]

Answer 1

我没试过，但你可以试试这个。在 Swift 中，您可以为连接类创建一个新的扩展文件。

extension Connection {
    public var userVersion: Int32 {
        get { return Int32(try! scalar("PRAGMA user_version") as! Int64)}
        set { try! run("PRAGMA user_version = \(newValue)") }
    }
}

注意：请检查以下代码的语法，因为我无法判断您的变量

如果表不存在，您的表将根据您的代码创建。

//in viewdidLoad of viewcontroller
if db.userVersion == 0 {
    // handle first migration
    do 
    {
        let offlineLocationTable = sqliteOfflineLocationTable.offlineLocationTable.create(ifNotExists: true) { (table) in
            table.column(sqliteOfflineLocationTable.id, primaryKey: true)
            table.column(sqliteOfflineLocationTable.status)
            table.column(sqliteOfflineLocationTable.loadid)
            table.column(sqliteOfflineLocationTable.jobid)
            table.column(sqliteOfflineLocationTable.lat)
            table.column(sqliteOfflineLocationTable.lng)
            // any other table entries
        }
        try self.db.run(offlineLocationTable)    
        // on complete of first table creation change the version
        db.userVersion = 1
    } catch {
        print(error)
    }
}
if db.userVersion == 1 {
    // handle second migration
    // Here we add New Column in table 
    do 
    {
        try self.db.run(offlineLocationTable.addColumn(t, defaultValue: ""))
        // any other modifications
        db.userVersion = 2
    } catch {
        print(error)
    }
}

现在编写您的任何其他代码。