SQLite数据库工具包GRDB.swift

GRDB.swift是一个SQLite数据库工具包，主要用于应用程序的开发。
与SQLite.swift或FMDB相比，GRDB可以为您提供大量的胶水代码。 与Core Data或Realm相比，它可以简化您的多线程应用程序。

打开数据库连接

import GRDB

// Simple database connection
let dbQueue = try DatabaseQueue(path: "/path/to/database.sqlite")

// Enhanced multithreading based on SQLite's WAL mode
let dbPool = try DatabasePool(path: "/path/to/database.sqlite")

执行SQL语句

try dbQueue.inDatabase { db in
    try db.execute(
        "CREATE TABLE pointOfInterests (" +
            "id INTEGER PRIMARY KEY, " +
            "title TEXT NOT NULL, " +
            "favorite BOOLEAN NOT NULL DEFAULT 0, " +
            "latitude DOUBLE NOT NULL, " +
            "longitude DOUBLE NOT NULL" +
        ")")

    try db.execute(
        "INSERT INTO pointOfInterests (title, favorite, latitude, longitude) " +
        "VALUES (?, ?, ?, ?)",
        arguments: ["Paris", true, 48.85341, 2.3488])
    
    let parisId = db.lastInsertedRowID
}

获取数据库行和值 

try dbQueue.inDatabase { db in
    let rows = try Row.fetchCursor(db, "SELECT * FROM pointOfInterests")
    while let row = try rows.next() {
        let title: String = row.value(named: "title")
        let isFavorite: Bool = row.value(named: "favorite")
        let coordinate = CLLocationCoordinate2D(
            latitude: row.value(named: "latitude"),
            longitude: row.value(named: "longitude"))
    }

    let poiCount = try Int.fetchOne(db, "SELECT COUNT(*) FROM pointOfInterests")! // Int
    let poiTitles = try String.fetchAll(db, "SELECT title FROM pointOfInterests") // [String]
}

// Extraction
let poiCount = try dbQueue.inDatabase { db in
    try Int.fetchOne(db, "SELECT COUNT(*) FROM pointOfInterests")!
}

添加并提取记录

struct PointOfInterest {
    var id: Int64?
    var title: String
    var isFavorite: Bool
    var coordinate: CLLocationCoordinate2D
}

// snip: turn PointOfInterest into a "record" by adopting the protocols that
// provide fetching and persistence methods.

try dbQueue.inDatabase { db in
    var berlin = PointOfInterest(
        id: nil,
        title: "Berlin",
        isFavorite: false,
        coordinate: CLLocationCoordinate2D(latitude: 52.52437, longitude: 13.41053))
    
    try berlin.insert(db)
    berlin.id // some value
    
    berlin.isFavorite = true
    try berlin.update(db)
    
    // Fetch [PointOfInterest] from SQL
    let pois = try PointOfInterest.fetchAll(db, "SELECT * FROM pointOfInterests")
}

不使用SQL进行查询

try dbQueue.inDatabase { db in
    try db.create(table: "pointOfInterests") { t in
        t.column("id", .integer).primaryKey()
        t.column("title", .text).notNull()
        t.column("favorite", .boolean).notNull().defaults(to: false)
        t.column("longitude", .double).notNull()
        t.column("latitude", .double).notNull()
    }
    
    // PointOfInterest?
    let paris = try PointOfInterest.fetchOne(db, key: 1)
    
    // PointOfInterest?
    let titleColumn = Column("title")
    let berlin = try PointOfInterest.filter(titleColumn == "Berlin").fetchOne(db)
    
    // [PointOfInterest]
    let favoriteColumn = Column("favorite")
    let favoritePois = try PointOfInterest
        .filter(favoriteColumn)
        .order(titleColumn)
        .fetchAll(db)
}