我正在使用sqlite.swift进行数据库创建。我已经借助此链接http://masteringswift.blogspot.in/2015/09/create-data-access-layer-with.html创建了一个类。我想在播放器表引用中的teamID（列）上创建一个外键作为团队表teamID（列）。
这是团队和玩家表的助手类：
class TeamDataHelper: DataHelperProtocol {
static let TABLE_NAME = "Teams"
static let table = Table(TABLE_NAME)
static let teamId = Expression<Int64>("teamid")
static let city = Expression<String>("city")
static let nickName = Expression<String>("nickname")
static let abbreviation = Expression<String>("abbreviation")
typealias T = Team
static func createTable() throws {
guard let DB = SQLiteDataStore.sharedInstance.BBDB else {
throw DataAccessError.Datastore_Connection_Error
}
do {
let _ = try DB.run( table.create(ifNotExists: true) {t in
t.column(teamId, primaryKey: true)
t.column(city)
t.column(nickName)
t.column(abbreviation)
})
} catch _ {
// Error throw if table already exists
}
}
static func insert(item: T) throws -> Int64 {
guard let DB = SQLiteDataStore.sharedInstance.BBDB else {
throw DataAccessError.Datastore_Connection_Error
}
if (item.city != nil && item.nickName != nil && item.abbreviation != nil) {
let insert = table.insert(city <- item.city!, nickName <- item.nickName!, abbreviation <- item.abbreviation!)
do {
let rowId = try DB.run(insert)
guard rowId > 0 else {
throw DataAccessError.Insert_Error
}
return rowId
} catch _ {
throw DataAccessError.Insert_Error
}
}
throw DataAccessError.Nil_In_Data
}
static func delete (item: T) throws -> Void {
guard let DB = SQLiteDataStore.sharedInstance.BBDB else {
throw DataAccessError.Datastore_Connection_Error
}
if let id = item.teamId {
let query = table.filter(teamId == id)
do {
let tmp = try DB.run(query.delete())
guard tmp == 1 else {
throw DataAccessError.Delete_Error
}
} catch _ {
throw DataAccessError.Delete_Error
}
}
}
static func find(id: Int64) throws -> T? {
guard let DB = SQLiteDataStore.sharedInstance.BBDB else {
throw DataAccessError.Datastore_Connection_Error
}
let query = table.filter(teamId == id)
let items = try DB.prepare(query)
for item in items {
return Team(teamId: item[teamId] , city: item[city], nickName: item[nickName], abbreviation: item[abbreviation])
}
return nil
}
static func findAll() throws -> [T]? {
guard let DB = SQLiteDataStore.sharedInstance.BBDB else {
throw DataAccessError.Datastore_Connection_Error
}
var retArray = [T]()
let items = try DB.prepare(table)
for item in items {
retArray.append(Team(teamId: item[teamId], city: item[city], nickName: item[nickName], abbreviation: item[abbreviation]))
}
return retArray
}
}
class PlayerDataHelper: DataHelperProtocol {
static let TABLE_NAME = "Players"
static let playerId = Expression<Int64>("playerid")
static let firstName = Expression<String>("firstName")
static let lastName = Expression<String>("lastName")
static let number = Expression<Int>("number")
static let teamId = Expression<Int64>("teamid")
static let position = Expression<String>("position")
static let table = Table(TABLE_NAME)
typealias T = Player
static func createTable() throws {
guard let DB = SQLiteDataStore.sharedInstance.BBDB else {
throw DataAccessError.Datastore_Connection_Error
}
do {
_ = try DB.run( table.create(ifNotExists: true) {t in
t.column(playerId, primaryKey: true)
t.column(firstName)
t.column(lastName)
t.column(number)
t.column(teamId)
t.column(position)
})
} catch _ {
// Error thrown when table exists
}
}
static func insert(item: T) throws -> Int64 {
guard let DB = SQLiteDataStore.sharedInstance.BBDB else {
throw DataAccessError.Datastore_Connection_Error
}
if (item.firstName != nil && item.lastName != nil && item.teamId != nil && item.position != nil) {
let insert = table.insert(firstName <- item.firstName!, number <- item.number!, lastName <- item.lastName!, teamId <- item.teamId!, position <- item.position!.rawValue)
do {
let rowId = try DB.run(insert)
guard rowId >= 0 else {
throw DataAccessError.Insert_Error
}
return rowId
} catch _ {
throw DataAccessError.Insert_Error
}
}
throw DataAccessError.Nil_In_Data
}
static func delete (item: T) throws -> Void {
guard let DB = SQLiteDataStore.sharedInstance.BBDB else {
throw DataAccessError.Datastore_Connection_Error
}
if let id = item.playerId {
let query = table.filter(playerId == id)
do {
let tmp = try DB.run(query.delete())
guard tmp == 1 else {
throw DataAccessError.Delete_Error
}
} catch _ {
throw DataAccessError.Delete_Error
}
}
}
static func find(id: Int64) throws -> T? {
guard let DB = SQLiteDataStore.sharedInstance.BBDB else {
throw DataAccessError.Datastore_Connection_Error
}
let query = table.filter(playerId == id)
let items = try DB.prepare(query)
for item in items {
return Player(playerId: item[playerId], firstName: item[firstName], lastName: item[lastName], number: item[number], teamId: item[teamId], position: Positions(rawValue: item[position]))
}
return nil
}
static func findAll() throws -> [T]? {
guard let DB = SQLiteDataStore.sharedInstance.BBDB else {
throw DataAccessError.Datastore_Connection_Error
}
var retArray = [T]()
let items = try DB.prepare(table)
for item in items {
retArray.append(Player(playerId: item[playerId], firstName: item[firstName], lastName: item[lastName], number: item[number], teamId: item[teamId], position: Positions(rawValue: item[position])))
}
return retArray
}
}
在上面的播放器表中，我想为teamID创建外键作为参考团队表teamID。如果我正在创建“t.foreignKey（teamID，on：TeamDataHelper.teamID）”之类的外键，那么它就会出错。
任何人都可以向我提出任何帮助。
答案 0 :(得分：0)
1.检查你的陈述。对于Swift 4（和Xcode 9），它应该是：
t.foreignKey(teamId, references: teamTable, teamId, delete: .setNull)
// FOREIGN KEY("teamid") REFERENCES "Team"("teamid") ON DELETE SET NULL
将它放在PlayerDataHelper类的createTable（）函数中的DB.run中
2.您还需要在PlayerDataHelper类中使用以下代码
teamTable = Table("Team")