问从核心数据中删除对象，还会追加空对象吗？
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Stack Overflow用户

提问于 2015-04-14 08:12:05

回答 1查看 842关注 0票数 2

我正在尝试设置一个UITableView，其中包含一个实体中的所有对象。

但是，我正在从api中加载数据。所以每次加载时，我都会删除实体中的所有对象。加上新的。

但是当我这么做的时候。它显示了5个带有api数据的单元格，每次加载它。它增加了5个空细胞。

它添加空单元格的原因是，我定义的对象数如下所示：

func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return stocks.count
}

有股票的地方：var stocks = [NSManagedObject]()

因此，我认为这是因为我的实体中有一些空的对象？

下面是我如何设置我的数据：

    func loadSuggestions(Formula: Int) {
    println("----- Loading Data -----")
    // Check for an internet connection
    if Reachability.isConnectedToNetwork() == false {
        println("ERROR: -> No Internet Connection <-")
    } else {

        // Delete all the current objects in the entity
        let fetchRequest = NSFetchRequest(entityName: formulaEntity)
        let a = managedContext.executeFetchRequest(fetchRequest, error: nil) as! [NSManagedObject]
        for mo in a {
            managedContext.deleteObject(mo)
            //println("removed \(mo)")
        }
        // save the context after removing objects.
        managedContext.save(nil)

        // Setting up a fetch request to get the api data.
        let entity =  NSEntityDescription.entityForName("\(formulaEntity)", inManagedObjectContext:managedContext)

        var request = NSURLRequest(URL: formulaAPI!)
        var data = NSURLConnection.sendSynchronousRequest(request, returningResponse: nil, error: nil)
        var formula = JSON(data: data!)

        for (index: String, actionable: JSON) in formula["actionable"] {
            stockName = actionable["name"].stringValue
            ticker = actionable["ticker"].stringValue
            action = actionable["action"].stringValue
            suggestedPrice = actionable["suggested_price"].floatValue
            weight = actionable["percentage_weight"].floatValue

            // Set the values in CoreData
            let stock = NSManagedObject(entity: entity!,insertIntoManagedObjectContext:managedContext)

            stock.setValue(stockName, forKey: "name")
            stock.setValue(ticker, forKey: "ticker")
            stock.setValue(action, forKey: "action")
            stock.setValue(suggestedPrice, forKey: "suggestedPrice")
            stock.setValue(weight, forKey: "weight")

            // Set up second api fetch
            var quoteAPI = NSURL(string: "http://dev.markitondemand.com/Api/v2/Quote/json?symbol=\(ticker)")

            var quoteRequest = NSURLRequest(URL: quoteAPI!)
            var quoteData = NSURLConnection.sendSynchronousRequest(quoteRequest, returningResponse: nil, error: nil)
            if quoteData != nil {
                var quote = JSON(data: quoteData!)
                betterStockName = quote["Name"].stringValue
                lastPrice = quote["LastPrice"].floatValue

                // Setting the last values in CoreData
                if betterStockName != "" {
                    stock.setValue(betterStockName, forKey: "name")
                }
                stock.setValue(lastPrice, forKey: "lastPrice")

            } else {
                println("ERROR - NO DATA")
            }

            var error: NSError?
            if !managedContext.save(&error) {
                println("Could not save \(error), \(error?.userInfo)")
            }
            // finally add the stockdata to the CoreData entity.
            stocks.append(stock)


        }



        // Reload the tableview with the new data.
        self.tableView.reloadData()
    }
}