如何从Core Data(swift)创建CSV文件 [英] How to create a CSV file from Core Data (swift)
问题描述
我正在构建一个应用程序,核心数据(1个实体具有5个属性)显示在tableView中。现在我想导出这个数据到CSV文件(所以我可以发送这个文件与邮件从手机),所以我可以在Excel上打开它。我搜索了很多,但没有找到正确的答案。有人可以帮助我或给我一个很好的解释或教程的链接?
I'm building an app with core data (1 entity with 5 attributes) that display in a tableView. Now i would like to export this data to a CSV file (so i can send this file with mail from phone) so i can open it in excel on a windows. i search a lot but didn't find the right answer. Can someone help me or give me a link to a good explanation or tutorial?
我正在建立swift btw。
I'm building in swift btw.
func createExportString() -> String {
var merk: String?
var ref: String?
var beschrijving: String?
var aantal: String?
var wbs: String?
var export = NSLocalizedString("merk, ref, beschrijving, aantal, wbs \n", comment: "")
merk = Lijst.valueForKey("merk") as? String
ref = Lijst.valueForKey("ref") as? String
aantal = Lijst.valueForKey("aantal") as? String
beschrijving = Lijst.valueForKey("beschrijving") as? String
wbs = Lijst.valueForKey("wbs") as? String
let merkString = "\(merk!)" ?? "-"
let refString = "\(ref!)" ?? "-"
let beschString = "\(beschrijving!)" ?? "-"
let aantalString = "\(aantal!)" ?? "-"
let wbsString = "\(wbs!)" ?? "-"
export += merkString + "," + refString + "," + beschString + "," + aantalString +
"," + wbsString + "\n"
print("This is what the app will export: \(export)")
return export
}
@IBAction func saveToCSV(sender: AnyObject) {
exportDatabase()
}
func exportDatabase() {
var exportString = createExportString()
saveAndExport(exportString)
}
func saveAndExport(exportString: String) {
let exportFilePath = NSTemporaryDirectory() + "export.csv"
let exportFileURL = NSURL(fileURLWithPath: exportFilePath)
NSFileManager.defaultManager().createFileAtPath(exportFilePath, contents: NSData(), attributes: nil)
var fileHandleError: NSError? = nil
var fileHandle: NSFileHandle? = nil
do {
fileHandle = try NSFileHandle(forWritingToURL: exportFileURL)
} catch {
print( "Error with fileHandle")
}
if fileHandle != nil {
fileHandle!.seekToEndOfFile()
let csvData = exportString.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false)
fileHandle!.writeData(csvData!)
fileHandle!.closeFile()
let firstActivityItem = NSURL(fileURLWithPath: exportFilePath)
let activityViewController: UIActivityViewController = UIActivityViewController(activityItems: [firstActivityItem], applicationActivities: nil)
self.presentViewController(activityViewController, animated: true, completion: nil)
}
}
推荐答案
这是一个简单的方法来做所有你想要的 - 传递管理对象的数组和一个字符串是CSV的文件名。该方法将CSV写入文件。我相信你已经在你的代码中有这么多,缺少的东西是最后两行,只是写一个字符串到一个新的文件Documents目录。
This is a concise way of doing all you want - you pass array of managed objects and a string that is CSV's filename. The method writes your CSV to a file. I believe you already have most of this in your code, the thing that is lacking are last two lines that just write a string into a new file in "Documents" directory.
func writeCoreDataObjectToCVS(objects: [NSManagedObject], named: String) -> String {
/* We assume that all objects are of the same type */
guard objects.count > 0 else {
return
}
let firstObject = objects[0]
let attribs = Array(firstObject.entity.attributesByName.keys)
let csvHeaderString = (attribs.reduce("",combine: {($0 as String) + "," + $1 }) as NSString).substringFromIndex(1) + "\n"
let csvArray = objects.map({object in
(attribs.map({(object.valueForKey($0) ?? "NIL").description}).reduce("",combine: {$0 + "," + $1}) as NSString).substringFromIndex(1) + "\n"
})
let csvString = csvArray.reduce("", combine: +)
return csvHeaderString+csvString
}
现在,代码中的其他地方你需要从这个字符串创建NSData,
Now, somewhere else in the code you need to create NSData from this string and add it to mail composer:
let csvString = .....
let data = csvString.dataUsingEncoding(NSUTF8StringEncoding)
let composer = MFMailComposeViewController()
composer.addAttachmentData(attachment: data,
mimeType mimeType: "text/csv",
fileName filename: "mydata.csv")
然后,使用作曲家做一些常用的操作(set body,topic等),并将其呈现给用户
Then, do the usual stuff with the composer (set body, topic, etc) and present it to the user!
编辑:
编辑答案以更好地回答问题。
Edited the answer to better answer the question.
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