I am trying to decompressed a Json data stream. I've found various decompression solutions, the native zlib seems easier, the other cocoa pod solutions produced new problems. The setting advised in native zlib inflate/deflate for swift3 on iOS seems working, the problem is what's next. I've thoroughly searched the net, only found C or Obj-C example codes but not Swift's. Thanks.
Another solution I tried was with https://github.com/mw99/DataCompression. But I had problem trying to set it up according to the instruction so look into the short codes and took out the part that I think should work for me, hard-coded some of the options. But no matter which algorithm I tried, perform() return nil.
I also tried unzip(), it failed at guard header >> 8 & 0b1111 == 0b1000. The web address automatic download a gzip file which can be decompressed into a Json file.
var routeFile: JsonRouteFile?
UIApplication.shared.isNetworkActivityIndicatorVisible = true
let urlRoute:URL = URL(string: "http://data.taipei/bus/ROUTE")!
DispatchQueue.global().async {
do {
let data:Data = try Data(contentsOf: urlRoute)
routeFile = try JSONDecoder().decode(JsonRouteFile?.self, from: data.decompress()!)
`
https://github.com/1024jp/GzipSwift works.
I didn't go through the enter installation though. Just dragged the file over.
Related
I'm writing an iOS Swift app to fetch metadata from DJI drone images. I'm trying to access the Xmp.drone-dji.X metadata. The iOS/Swift CGImageSource and CGImageMetadata libraries/classes get almost all of the metadata out of the image but not the Xmp.drone-dji. When I get a list of tags, those tag/values are not listed. I know the tags/data are in the images because I've examined the images using exif, exiv2, etc.
Any suggestions?
Here is the code I'm using so far:
result.itemProvider.loadDataRepresentation(forTypeIdentifier: UTType.image.identifier)
{ data, err in
if let data = data {
let src = CGImageSourceCreateWithData(data as CFData,nil)!
let md = CGImageSourceCopyPropertiesAtIndex(src,0,nil) as! NSDictionary
let md2 = CGImageSourceCopyMetadataAtIndex(src,0,nil)
}
Thanks,
Bobby
So, after a lot of searching, trial and error, I have found an answer.
I was not able to get any of the CGImage swift libraries to extract this info for me.
Adobe has a c++ library that parses xmp/xml data out of images and it purports to support iOS. I didnt want the hassle of building c++ on iOS, importing that into Xcode and then dealing with the fact that thrown errors do not propagate well from c++/objectiveC to Swift.
So, at a high level, I did the following:
get the bytes of the raw image as CFData or Data then cast to a String
then use String.range() to find beginning of XML/XMP data in image
searching for substring <?xpacket begin
use String.range() to find end of XML/XMP data in image
using substring <?xpacket end.*?>
Extract the XML document out of image data String
Use Swift XMLParser class to parse the XML and then copying attributes and
elements as necessary. I just simply added what I wanted to already
existing Exif NSdictionary returned by CGImage classes.
Happy to answer questions on this approach. My code will eventually be uploaded to GitHub under OpenAthenaIOS project.
Bobby
I got little problem, I am downloading PDF and saving to location, I am using write method to save to location and everything seems to work on version iOS 10 and below, but I got problem with iOS11, I am getting false from method below, I checked path, and bytes and it is same on both devices.
(try? data.write(to: invoiceFileUrl, options: [.atomic])) != nil
try this
let data = NSData(contentsOf:url! as URL)
data?.write(to:invoiceFileUrl, atomically: true)
Have you tried simply moving the file around? I am guessing you are using URLSession to download said file ( or you should anyway ).
Then you can use FileManager to move the temporary file to your documents or whatever desired directory in your app's container.
FileManager.default.moveItem(at:temporaryURL, to: destinationURL)
In case you prefer using paths there is also:
FileManager.default.moveItem(atPath: temporaryPath, toPath: destinationPath)
Though I personally don't use paths often (anymore) because it can lead to a whole load of inconsistencies and other issues you just don't want to deal with. Whatever backend you have try to move to NSURL or URL as quickly as you can with any received data; it'll make your life easier and most importantly more consistent accross foundation API's.
moveItemAtURL - Foundation documentation
This is my swift code simplified:
func readContent(url:NSURL!){
do {
let file: NSFileHandle? = try NSFileHandle(forReadingFromURL: url)
if (file != nil){
file?.seekToFileOffset(10)
let content=file!.readDataOfLength(5)
print(String(data: content, encoding: NSASCIIStringEncoding))
file!.closeFile()
}
}catch {
}
}
I am building a file reader, that could read text files and pdfs. I am using NSFileHandler because I need to keep track of the position where the reading is happening.
I am able to read text files without a problem. However with pdfs I am having two problems:
How do I get the type of encoding used to encore the pdf? NSASCIIStringEncoding for instance does not work fine with text file but not with the pdf file. I am getting strange characters. I imaging that there is a way to detect the encoding. I have been following https://developer.apple.com/library/ios/documentation/FileManagement/Conceptual/FileSystemProgrammingGuide/Introduction/Introduction.html and I haven't found anything addressing this issue on stack overflow.
Given the fact that pdfs may contain text, images and videos how do I identify these contents while reading.. I read that magic numbers might do it https://en.wikipedia.org/wiki/Magic_number_(programming)#Magic_numbers_in_files but I read that there are not advisable http://www.techrepublic.com/article/avoid-using-magic-numbers-and-string-literals-in-your-code/. In addition I have not yet found a guide on how to use them.
please note that it is important for me to keep track of the Offset while reading.
When I run the following code in Xcode with iOS simulator selected it parses without a problem, but when I run it on a device (iPhone 5c) I get:
Failed to load xml
XML parsing failed at 0:0: Optional("The operation couldn’t be completed. (Cocoa error -1.)")
I tried different xml files, but it looks like its a security issue!?
Should I set permission in my project somewhere?
let url:String="http://images.apple.com/main/rss/hotnews/hotnews.rss#sthash.TyhRD7Zy.dpuf"
let urlToSend: NSURL = NSURL(string: url)!
parser = NSXMLParser(contentsOfURL: urlToSend)!
parser.delegate = self
if !parser.parse() {
let error = parser.parserError
let line = parser.lineNumber
let col = parser.columnNumber
print("XML parsing failed at \(line):\(col): \(error?.localizedDescription)")
}`
To help isolate the error, it might be helpful to load the contents of the URL into a string first – that would help you isolate whether it's a security problem or a parsing problem. You might also want take away the force unwraps and use if/let so you can see the flow of errors more clearly.
That being said, here are some things to check:
1) Is the device online?
2) Is the device connected to a proxy, VPN or other intermediary that blocks some resources?
3) Is the device able to reach that URL when you use Safari?
4) Is your parser able to read other RSS feeds?
In my experience, 2) is often the problem.
Is there any way to turn a string into a block of code? I'm making an Ajax request to a website of mine that has an endpoint that returns some swift code as a string. I can get that code back as a string, but I can't run that code because it doesn't know that it is code.
As others have pointed out, if you are creating an iOS app (especially for distribution on the app store), you can not do this. However, if you are writing Swift code for an OS X machine AND you know that XCode is installed on the machine, you can run your Swift code string by running the command-line Swift compiler. Something like this (with proper error checking, of course):
var str = "let str = \"Hello\"\nprintln(\"\\(str) world\")\n"
let task = Process()
task.launchPath = "/usr/bin/swift"
let outpipe = Pipe()
let inpipe = Pipe()
inpipe.fileHandleForWriting.write(str.data(using: String.Encoding.utf8, allowLossyConversion: true)!)
task.standardInput = inpipe
task.standardOutput = outpipe
task.launch()
task.waitUntilExit()
task.standardInput = Pipe()
let data = outpipe.fileHandleForReading.readDataToEndOfFile()
let output = NSString(data: data, encoding: String.Encoding.utf8.rawValue)! as String
Again, this is probably not recommended in nearly all real-world cases, but is a way you can execute a String of Swift code, if you really need to.
No, you can't do that. Swift is a compiled language, not interpreted like Ajax.
The Swift compiler runs on your Mac, not on the iOS device. (The same is true for Objective-C).
Plus, Apple's app store guidelines forbid delivering executable code to your apps, so even if you figured out a way to do it, your app would be rejected.
Edit:
Note that with the advent of Swift playgrounds, it is possible to run the Swift compiler on an iPad. Recent high-end iPhones are probably also up to the job, but you'd have to figure out how to get it installed.
As stated above though, Apple's app store guidelines forbid you from delivering code to your apps at runtime.