Question

关于我的应用程序的一些背景：我正在绘制地图。当用户移动地图时，我将执行数据库查询。我首先执行rTree查询，以查找将在当前视口中绘制的要素。获得这些ID后，我将执行第二次数据库查询，以从数据库中提取要素（geojson）。我进行快速检查以查看是否已经绘制了该项目，否则，我进行了addChild来在地图上渲染地图项。我想通过GCD在后台查找这些数据库，以便用户可以平滑地移动地图。我已经实现了这一点，但是内存使用量迅速增长到了1gb，而如果我在主线程中完成所有工作，则它将占用250mb（我可以接受）。我假设由于使用闭包而未清除某些内容。感谢您对导致内存泄漏的原因有深入的了解。

public func drawItemsInBox(boundingBox: [Double]) {
        DispatchQueue.global(qos: .background).async { [weak self] in
            guard let self = self else {
                return
            }

            var drawItems: [Int64] = []
            let table = Table("LNDARE_XS")
            let tableRTree = Table("LNDARE_XS_virtual")
            let coords = Expression<String?>("coords")
            let foid = Expression<String>("foid")
            let rTree = Expression<Int64>("rTree")
            let minX = Expression<Double>("minX")
            let maxX = Expression<Double>("maxX")
            let minY = Expression<Double>("minY")
            let maxY = Expression<Double>("maxY")
            let id = Expression<Int64>("id")

            // find all the features to draw via an rTree query
            for row in try! self.db.prepare(tableRTree.filter(maxX >= boundingBox[0] && minX <= boundingBox[1] && maxY >= boundingBox[2] && minY <= boundingBox[3])) {
                drawItems.append(row[id])
            }

            do {
                // get all the features geojson data
                let query = table.filter(drawItems.contains(rTree))
                for row in try self.db.prepare(query) {

                    // skip drawing if the feature already exists on the map
                    if self.featureTracking["LNDARE_XS"]?[Int64(row[foid])!] == nil {

                        // convert the database string to an array of coords
                        var toBeRendered:[CGPoint] = []
                        let coordsArray = row[coords]!.components(separatedBy: ",")

                        for i in 0...(coordsArray.count / 2) - 1 {
                            toBeRendered.append(CGPoint(x: (Double(coordsArray[i*2])!), y: (Double(coordsArray[(i*2)+1])!)))
                        }

                        let linearShapeNode = SKShapeNode(points: &toBeRendered, count: toBeRendered.count)
                        linearShapeNode.position = CGPoint(x: self.frame.midX, y: self.frame.midY)
                        linearShapeNode.lineWidth = 0
                        linearShapeNode.fillColor = NSColor.black

                        // append the featureId for tracking and call addChild to draw
                        self.scaleLayer.addChild(linearShapeNode)
                        self.featureTracking["LNDARE_XS"]?[Int64(row[foid])!] = linearShapeNode
                    }
                }
            } catch {
                // catch
            }
        }
    }

Answer 1

也许更改toBeRendered可以保存一些内容：

  var toBeRendered:[CGPoint] = []
            for row in try self.db.prepare(query) {

                // skip drawing if the feature already exists on the map
                if self.featureTracking["LNDARE_XS"]?[Int64(row[foid])!] == nil {

                    // convert the database string to an array of coords
                    toBeRendered.removeAll()
                    let coordsArray = row[coords]!.components(separatedBy: ",")

                    for i in 0...(coordsArray.count / 2) - 1 {
                        toBeRendered.append(CGPoint(x: (Double(coordsArray[i*2])!), y: (Double(coordsArray[(i*2)+1])!)))
                    }

Answer 2

由于您不在主线程上，因此可能尝试使用自动释放池

public func drawItemsInBox(boundingBox: [Double]) {
    DispatchQueue.global(qos: .background).async { [weak self] in
        guard let self = self else {
            return
        }

        var drawItems: [Int64] = []
        let table = Table("LNDARE_XS")
        let tableRTree = Table("LNDARE_XS_virtual")
        let coords = Expression<String?>("coords")
        let foid = Expression<String>("foid")
        let rTree = Expression<Int64>("rTree")
        let minX = Expression<Double>("minX")
        let maxX = Expression<Double>("maxX")
        let minY = Expression<Double>("minY")
        let maxY = Expression<Double>("maxY")
        let id = Expression<Int64>("id")

        // find all the features to draw via an rTree query
        for row in try! self.db.prepare(tableRTree.filter(maxX >= boundingBox[0] && minX <= boundingBox[1] && maxY >= boundingBox[2] && minY <= boundingBox[3])) {
            drawItems.append(row[id])
        }

        do {
            // get all the features geojson data
            let query = table.filter(drawItems.contains(rTree))
            for row in try self.db.prepare(query) {
                autoreleasepool{
                    // skip drawing if the feature already exists on the map
                    if self.featureTracking["LNDARE_XS"]?[Int64(row[foid])!] == nil {

                        // convert the database string to an array of coords
                        var toBeRendered:[CGPoint] = []
                        let coordsArray = row[coords]!.components(separatedBy: ",")

                        for i in 0...(coordsArray.count / 2) - 1 {
                        toBeRendered.append(CGPoint(x: (Double(coordsArray[i*2])!), y: (Double(coordsArray[(i*2)+1])!)))
                        }

                        let linearShapeNode = SKShapeNode(points: &toBeRendered, count: toBeRendered.count)
                        linearShapeNode.position = CGPoint(x: self.frame.midX, y: self.frame.midY)
                        linearShapeNode.lineWidth = 0
                        linearShapeNode.fillColor = NSColor.black

                        // append the featureId for tracking and call addChild to draw
                        self.scaleLayer.addChild(linearShapeNode)
                        self.featureTracking["LNDARE_XS"]?[Int64(row[foid])!] = linearShapeNode
                    }
                }
            }
        } catch {
            // catch
        }
    }
}

在Swift GCD.async调用中识别内存泄漏

2 个答案: