I have a string "John+20", I would like to extract out "John", so, I tried following based on this answer:
// data contains value "John+20"
static func getName(fromString data: String?) {
guard let myData = data else {
return
}
let idx = myData.index(of: "+")
//Compiler ERROR: Generic parameter 'Self' could not be inferred
let name = String(myData[..<idx])
}
But I get the error I mentioned in code comment, why is that?
I am using Swift 4.1 in my iOS project.
I guess the index is an optional as well. Try :
// data contains value "John+20"
static func getName(fromString data: String?) {
guard let myData = data else, let idx = myData.index(of: "+") {
return
}
let name = String(myData[..<idx])
}
Related
I am trying to read from Firestore into a Dictionary[Any] type using Struct. I can get the values loaded into variable "data" dictionary with Any type.
However I cannot loop thru it to access normal nested Dictionary variable.
I cannot get Key, values printed.
Following is my code:
class PullQuestions {
//shared instance variable
**public var data = [Any]()**
private var qdb = Firestore.firestore()
public struct questionid
{
let qid : String
var questions : [basequestion]
var answers: [baseans]
}
public struct basequestion {
let category : String
let question : String
}
public struct baseans {
let answer : String
}
class var sharedManager: PullQuestions {
struct Static {
static let instance = PullQuestions()
}
return Static.instance
}
static func getData(completion: #escaping (_ result: [Any]) -> Void) {
let rootCollection = PullQuestions.sharedManager.qdb.collection("questions")
//var data = [Any]()
rootCollection.order(by: "upvote", descending: false).getDocuments(completion: {
(querySnapshot, error) in
if error != nil {
print("Error when getting data \(String(describing: error?.localizedDescription))")
} else {
guard let topSnapshot = querySnapshot?.documents else { return }
// var questiondoc = [basequestion]()
for questioncollection in topSnapshot {
rootCollection.document(questioncollection.documentID).collection("answers").getDocuments(completion: {
(snapshot, err) in
guard let snapshot = snapshot?.documents else { return }
var answers = [baseans]()
for document in snapshot { //There should be only one Document for each answer collection
//Read thru all fields
for i in 0..<document.data().count
{
let newAns = baseans(answer: answer)
print("Answer Docs=>", (answer))
answers.append(newAns)
}
}
let qid = questioncollection.documentID
let category = questioncollection.data()["category"] as! String
let question = questioncollection.data()["question"] as! String
let newQuestions = basequestion(category: category ,question: question)
let newQuestionDict = questionid(qid: qid, questions: [newQuestions], answers: answers)
PullQuestions.sharedManager.data.append(newQuestionDict)
//Return data on completion
completion(PullQuestions.sharedManager.data)
})
}
}
})
}
}
I can print like this
print("Count =>", (PullQuestions.sharedManager.data.count))
// print(PullQuestions.sharedManager.data.first ?? "Nil")
print(PullQuestions.sharedManager.data[0])
for element in PullQuestions.sharedManager.data
{
print("Elements in data:=>", (element))
}
I could access only the key.. how do i go and get the nested values ?
First of all, consider using Swift code conventions (e.g. your structs are named with small letters, but you should start with capital), this will make your code more readable.
Returning to your question. You use an array instead of dictionary (this piece of code: public var data = [Any]()). And here you are trying to print values:
for element in PullQuestions.sharedManager.data
{
print("Elements in data:=>", (element))
}
In this context element is an Any object, thus you cannot access any underlying properties. In order to do this you have two options:
1. You should specify the type of array's objects in it's declaration like this:
public var data = [questionid]()
or you can user this:
public var data: [questionid] = []
These two are equals, use the one you prefer.
2. If for any reasons you don't want to specify the type in declaration, you can cast it in your loop. Like this:
for element in PullQuestions.sharedManager.data
{
if let element = element as? quetionid {
print("Elements in data:=>", (element))
// you can also print element.qid, element.questions, element.answers
} else {
print("Element is not questionid")
}
}
You could of course use the force cast:
let element = element as! questionid
and avoid if let syntax (or guard let if you prefer), but I wouldn't recommend this, because it (potentially) can crash your app if element will be nil or any other type.
I want to have a random emoji inside a Label and every tableViewCell should show a different, random picked emoji...
I tried following function, but sadly it's giving me following error: Value of type '[String]' has no member 'shuffled'
let emojis: [String] = {
let url = Bundle.main.url(forResource: "emojis", withExtension: "txt")!
let list = try! String(contentsOf: url).map { String($0) }
return list.shuffled()
}()
po String(UnicodeScalar(Array(0x1F300...0x1F3F0).randomElement()!)!)
As Carpsen says, the shuffled() function is only in Swift ≤ 4.2. In earlier versions of the language you have to write your own.
Here is an example implementation. I called my scrambled(), so it will work in any version of Swift including 4.2:
extension Array {
func scrambled () -> [Element] {
var source = self
var dest = Array<Element>()
for _ in 1...self.count {
let index = Int(arc4random_uniform(UInt32(source.count)))
dest.append(source.remove(at: index))
}
return dest
}
}
You could scramble the entire set of emojis, but it seems to me you'd be better off creating an array of random emoji when you first populate the data source of your table view. To do that you could use a function randomEmoji():
func randomEmoji() -> String {
let range = 0x1F300...0x1F3F0
let index = Int(arc4random_uniform(UInt32(range.count)))
let ord = range.lowerBound + index
guard let scalar = UnicodeScalar(ord) else { return "❓" }
return String(scalar)
}
So you'd create a stuct to hold all the data for a table view cell, and then populate each struct with a call to randomEmoji().
Note that the randomEmoji() function only chooses emoji in the unicode range from 0x1F300 to 0x1F3F0. Also, the approach of using randomEmoji() may cause duplicate emoji.
You can easily use this extension for emoji string :)
extension NSObject {
public var emojiString: String {
let pointer = Unmanaged.passUnretained(self).toOpaque()
// You can adjust your range
//let range = 0x1F600...0x1F64F
let range = 0x1F300...0x1F3F0
let index = (pointer.hashValue % range.count)
let ord = range.lowerBound + index
guard let scalar = UnicodeScalar(ord) else { return "❓" }
return String(scalar)
}
}
Just call cell.textLabel?.text = cell.emojiString and you're good to go.
Unless you are using Swift 4.2, the shuffled()is not available and the error message is spot on.
You could create your own shuffled() function.
I have a method that loads an array of dictionaries from a propertylist. Then I change those arrays of dictionaries to array of a defined custom type;
I want to write that method in generic form so I call that method with the type I expect, then the method loads it and returns an array of my custom type rather than dictionaries
func loadPropertyList(fileName: String) -> [[String:AnyObject]]?
{
if let path = NSBundle.mainBundle().pathForResource(fileName, ofType: "plist")
{
if let plistXML = NSFileManager.defaultManager().contentsAtPath(path)
{
do {
if let temp = try NSPropertyListSerialization.propertyListWithData(plistXML, options: .Immutable, format: nil) as? [[String:AnyObject]]
{
return temp
}
}catch{}
}
}
return nil
}
//
func loadList<T>(fileName: String) -> [T]?{//**Here the answer I am expecting**}
I am assuming your function to read from a Plist works and that you don't want to subclass NSObject.
Since Swift reflecting does not support setting values this is not possible without some implementation for each Type you want this to work for.
It can however be done in a pretty elegant way.
struct PlistUtils { // encapsulate everything
static func loadPropertyList(fileName: String) -> [[String:AnyObject]]? {
if let path = NSBundle.mainBundle().pathForResource(fileName, ofType: "plist") {
if let plistXML = NSFileManager.defaultManager().contentsAtPath(path) {
do {
if let temp = try NSPropertyListSerialization.propertyListWithData(plistXML, options: .Immutable, format: nil) as? [[String:AnyObject]] {
return temp
}
} catch {
return nil
}
}
}
return nil
}
}
This protocol will be used in a generic fashion to get the Type name and read the corresponding Plist.
protocol PListConstructible {
static func read() -> [Self]
}
This protocol will be used to implement Key Value setters.
protocol KeyValueSettable {
static func set(fromKeyValueStore values:[String:AnyObject]) -> Self
}
This is the combination of both to generate an array of objects. This does require that the Plist is named after the Type.
extension PListConstructible where Self : KeyValueSettable {
static func read() -> [Self] {
let name = String(reflecting: self)
var instances : [Self] = []
if let data = PlistUtils.loadPropertyList(name) {
for entry in data {
instances.append(Self.set(fromKeyValueStore: entry))
}
}
return instances
}
}
This is some Type.
struct Some : PListConstructible {
var alpha : Int = 0
var beta : String = ""
}
All you have to do is implement the Key Value setter and it will now be able to be read from a Plist.
extension Some : KeyValueSettable {
static func set(fromKeyValueStore values: [String : AnyObject]) -> Some {
var some = Some()
some.alpha = (values["alpha"] as? Int) ?? some.alpha
some.beta = (values["beta"] as? String) ?? some.beta
return some
}
}
This is how you use it.
Some.read()
I want to load a PDF that is in my application bundle into a CGPDFDocument.
Is there some way of calling a function that if any of the parameters that don't accept options have values that are nil, the function isn't called and nil is returned.
eg:
let pdfPath : String? = NSBundle.mainBundle().pathForResouce("nac_06", ofType:"pdf")
//I want to do this
let data : NSData? = NSData(contentsOfFile:pdfPath)
//I have to do this
let data : NSData? = pdfPath != nil ? NSData(contentsOfFile:pdfPath) : nil
let doc : CGPDFDocumentRef? = CGPDFDocumentCreateWithProvider(CGDataProviderCreateWithCFData(data));
//pageView.pdf is optional, nicely this function accepts the document as an optional
pageView.pdfPage = CGPDFDocumentGetPage(doc, 1);
Because NSData.init?(contentsOfFile path:String), doesn't define path as optional, even though it is has an optional return value, I have to check before and if the parameter is nil, return nil. Is there some syntactic sugar for the data assignment (instead of the ?: operator)?
Either use multiple optional bindings separated by commas
func loadPDF() -> CGPDFDocumentRef?
{
if let pdfPath = NSBundle.mainBundle().pathForResouce("nac_06", ofType:"pdf"),
data = NSData(contentsOfFile:pdfPath),
doc = GPDFDocumentCreateWithProvider(CGDataProviderCreateWithCFData(data)) {
return doc
} else {
return nil
}
}
or use the guard statement
func loadPDF() -> CGPDFDocumentRef?
{
guard let pdfPath = NSBundle.mainBundle().pathForResouce("nac_06", ofType:"pdf") else { return nil }
guard let data = NSData(contentsOfFile:pdfPath) else { return nil }
return GPDFDocumentCreateWithProvider(CGDataProviderCreateWithCFData(data))
}
All explicit type annotations are syntactic sugar and not needed.
Edit:
In your particular case you need only to check if the file exists and even this – the file is missing – is very unlikely in iOS. Another benefit is to be able to return a non-optional PDFDocument.
func loadPDF() -> CGPDFDocumentRef
{
guard let pdfPath = NSBundle.mainBundle().pathForResource("nac_06", ofType:"pdf") else {
fatalError("file nac_06.pdf does not exist")
}
let data = NSData(contentsOfFile:pdfPath)
return CGPDFDocumentCreateWithProvider(CGDataProviderCreateWithCFData(data!))!
}
I assume that you also don't want to continue with the execution of the function if pdfPath or data is nil. In this case, guard would be the best choice:
guard let pdfPath = NSBundle.mainBundle().pathForResouce("nac_06", ofType:"pdf") else {
// eventually also report some error
return
}
guard let data = NSData(contentsOfFile:pdfPath) else {
// eventually also report some error
return
}
// at this point you have a valid data object
You could also combine this into a single guard statement, to reduce the code duplication, you'll loose however in this case the possibility to know which of the two failed.
guard let pdfPath = NSBundle.mainBundle().pathForResource("nac_06", ofType:"pdf"),
data = NSData(contentsOfFile:pdfPath) else {
// eventually also report some error
return
}
There is two ways to achieve this.
Extend NSData class and create your own convenience init? method
Use the guard statement
I prefer the second method:
func getPDF(path : String?) -> CGPDFDocumentRef?
{
guard let filePath = path,
data = NSData(contentsOfFile: filePath),
pdf = GPDFDocumentCreateWithProvider(CGDataProviderCreateWithCFData(data)) else
{
return nil
}
return pdf
}
Call the method like:
let doc = getPDF(path : NSBundle.mainBundle().pathForResouce("nac_06", ofType:"pdf"))
You could do something fancy by defining a custom operator to deal with this situation. For example:
infix operator ^> {associativity left precedence 150}
func ^><T, U>(arg: T?, f: T->U?) -> U?{
if let arg = arg {
return f(arg)
} else {
return nil
}
}
The operator takes an optional left-side argument and a function that takes a non-optional and returns another optional as a right-side argument.
You could then write your code like this:
let pdfPath = NSBundle.mainBundle().pathForResource("nac_06", ofType:"pdf")
//the line below needs a NSData extension
let data = pdfPath ^> NSData.fileContents
let doc = data ^> CGDataProviderCreateWithCFData ^> CGPDFDocumentCreateWithProvider
//pageView.pdf is optional, nicely this function accepts the document as an optional
pageView.pdfPage = CGPDFDocumentGetPage(doc, 1)
Note that for this to work you need to add an extension to NSData, as you cannot map the init(contentsOfFile:) initializer to a generic function that can be passed to ^>.
extension NSData {
class func fileContents(path: String) -> NSData? {
return NSData(contentsOfFile: path)
}
}
The usage of the ^> operator reverts however the order you write the function names, if you prefer having the function names in the same order as the original code, you can add a reversed operator that does the same thing:
infix operator ^< {associativity right precedence 150}
func ^< <T, U>(f: T->U?, arg: T?) -> U?{
if let arg = arg {
return f(arg)
} else {
return nil
}
}
let pdfPath = NSBundle.mainBundle().pathForResource("nac_06", ofType:"pdf")
let data = NSData.fileContents ^< pdfPath
let doc = CGPDFDocumentCreateWithProvider ^< CGDataProviderCreateWithCFData ^< data
//pageView.pdf is optional, nicely this function accepts the document as an optional
pageView.pdfPage = CGPDFDocumentGetPage(doc, 1)
Given the name of a file in the bundle, I want load the file into my Swift app. So I need to use this method:
let soundURL = NSBundle.mainBundle().URLForResource(fname, withExtension: ext)
For whatever reason, the method needs the filename separated from the file extension. Fine, it's easy enough to separate the two in most languages. But so far I'm not finding it to be so in Swift.
So here is what I have:
var rt: String.Index = fileName.rangeOfString(".", options:NSStringCompareOptions.BackwardsSearch)
var fname: String = fileName .substringToIndex(rt)
var ext = fileName.substringFromIndex(rt)
If I don't include the typing on the first line, I get errors on the two subsequent lines. With it, I'm getting an error on the first line:
Cannot convert the expression's type '(UnicodeScalarLiteralConvertible, options: NSStringCompareOptions)' to type 'UnicodeScalarLiteralConvertible'
How can I split the filename from the extension? Is there some elegant way to do this?
I was all excited about Swift because it seemed like a much more elegant language than Objective C. But now I'm finding that it has its own cumbersomeness.
Second attempt: I decided to make my own string-search method:
func rfind(haystack: String, needle: Character) -> Int {
var a = Array(haystack)
for var i = a.count - 1; i >= 0; i-- {
println(a[i])
if a[i] == needle {
println(i)
return i;
}
}
return -1
}
But now I get an error on the line var rt: String.Index = rfind(fileName, needle: "."):
'Int' is not convertible to 'String.Index'
Without the cast, I get an error on the two subsequent lines.
Can anyone help me to split this filename and extension?
Swift 5.0 update:
As pointed out in the comment, you can use this.
let filename: NSString = "bottom_bar.png"
let pathExtention = filename.pathExtension
let pathPrefix = filename.deletingPathExtension
This is with Swift 2, Xcode 7: If you have the filename with the extension already on it, then you can pass the full filename in as the first parameter and a blank string as the second parameter:
let soundURL = NSBundle.mainBundle()
.URLForResource("soundfile.ext", withExtension: "")
Alternatively nil as the extension parameter also works.
If you have a URL, and you want to get the name of the file itself for some reason, then you can do this:
soundURL.URLByDeletingPathExtension?.lastPathComponent
Swift 4
let soundURL = NSBundle.mainBundle().URLForResource("soundfile.ext", withExtension: "")
soundURL.deletingPathExtension().lastPathComponent
Works in Swift 5. Adding these behaviors to String class:
extension String {
func fileName() -> String {
return URL(fileURLWithPath: self).deletingPathExtension().lastPathComponent
}
func fileExtension() -> String {
return URL(fileURLWithPath: self).pathExtension
}
}
Example:
let file = "image.png"
let fileNameWithoutExtension = file.fileName()
let fileExtension = file.fileExtension()
Solution Swift 4
This solution will work for all instances and does not depend on manually parsing the string.
let path = "/Some/Random/Path/To/This.Strange.File.txt"
let fileName = URL(fileURLWithPath: path).deletingPathExtension().lastPathComponent
Swift.print(fileName)
The resulting output will be
This.Strange.File
In Swift 2.1 String.pathExtension is not available anymore. Instead you need to determine it through NSURL conversion:
NSURL(fileURLWithPath: filePath).pathExtension
In Swift you can change to NSString to get extension faster:
extension String {
func getPathExtension() -> String {
return (self as NSString).pathExtension
}
}
Latest Swift 4.2 works like this:
extension String {
func fileName() -> String {
return URL(fileURLWithPath: self).deletingPathExtension().lastPathComponent
}
func fileExtension() -> String {
return URL(fileURLWithPath: self).pathExtension
}
}
In Swift 2.1, it seems that the current way to do this is:
let filename = fileURL.URLByDeletingPathExtension?.lastPathComponent
let extension = fileURL.pathExtension
Swift 5 with code sugar
extension String {
var fileName: String {
URL(fileURLWithPath: self).deletingPathExtension().lastPathComponent
}
var fileExtension: String{
URL(fileURLWithPath: self).pathExtension
}
}
SWIFT 3.x Shortest Native Solution
let fileName:NSString = "the_file_name.mp3"
let onlyName = fileName.deletingPathExtension
let onlyExt = fileName.pathExtension
No extension or any extra stuff
(I've tested. based on #gabbler solution for Swift 2)
Swift 5
URL.deletingPathExtension().lastPathComponent
Strings in Swift can definitely by tricky. If you want a pure Swift method, here's how I would do it:
Use find to find the last occurrence of a "." in the reverse of the string
Use advance to get the correct index of the "." in the original string
Use String's subscript function that takes an IntervalType to get the strings
Package this all up in a function that returns an optional tuple of the name and extension
Something like this:
func splitFilename(str: String) -> (name: String, ext: String)? {
if let rDotIdx = find(reverse(str), ".") {
let dotIdx = advance(str.endIndex, -rDotIdx)
let fname = str[str.startIndex..<advance(dotIdx, -1)]
let ext = str[dotIdx..<str.endIndex]
return (fname, ext)
}
return nil
}
Which would be used like:
let str = "/Users/me/Documents/Something.something/text.txt"
if let split = splitFilename(str) {
println(split.name)
println(split.ext)
}
Which outputs:
/Users/me/Documents/Something.something/text
txt
Or, just use the already available NSString methods like pathExtension and stringByDeletingPathExtension.
Swift 5
URL(string: filePath)?.pathExtension
Try this for a simple Swift 4 solution
extension String {
func stripExtension(_ extensionSeperator: Character = ".") -> String {
let selfReversed = self.reversed()
guard let extensionPosition = selfReversed.index(of: extensionSeperator) else { return self }
return String(self[..<self.index(before: (extensionPosition.base.samePosition(in: self)!))])
}
}
print("hello.there.world".stripExtension())
// prints "hello.there"
Swift 3.0
let sourcePath = NSURL(string: fnName)?.pathExtension
let pathPrefix = fnName.replacingOccurrences(of: "." + sourcePath!, with: "")
Swift 3.x extended solution:
extension String {
func lastPathComponent(withExtension: Bool = true) -> String {
let lpc = self.nsString.lastPathComponent
return withExtension ? lpc : lpc.nsString.deletingPathExtension
}
var nsString: NSString {
return NSString(string: self)
}
}
let path = "/very/long/path/to/filename_v123.456.plist"
let filename = path.lastPathComponent(withExtension: false)
filename constant now contains "filename_v123.456"
A better way (or at least an alternative in Swift 2.0) is to use the String pathComponents property. This splits the pathname into an array of strings. e.g
if let pathComponents = filePath.pathComponents {
if let last = pathComponents.last {
print(" The last component is \(last)") // This would be the extension
// Getting the last but one component is a bit harder
// Note the edge case of a string with no delimiters!
}
}
// Otherwise you're out of luck, this wasn't a path name!
They got rid of pathExtension for whatever reason.
let str = "Hello/this/is/a/filepath/file.ext"
let l = str.componentsSeparatedByString("/")
let file = l.last?.componentsSeparatedByString(".")[0]
let ext = l.last?.componentsSeparatedByString(".")[1]
A cleaned up answer for Swift 4 with an extension off of PHAsset:
import Photos
extension PHAsset {
var originalFilename: String? {
if #available(iOS 9.0, *),
let resource = PHAssetResource.assetResources(for: self).first {
return resource.originalFilename
}
return value(forKey: "filename") as? String
}
}
As noted in XCode, the originalFilename is the name of the asset at the time it was created or imported.
Maybe I'm getting too late for this but a solution that worked for me and consider quite simple is using the #file compiler directive. Here is an example where I have a class FixtureManager, defined in FixtureManager.swift inside the /Tests/MyProjectTests/Fixturesdirectory. This works both in Xcode and withswift test`
import Foundation
final class FixtureManager {
static let fixturesDirectory = URL(fileURLWithPath: #file).deletingLastPathComponent()
func loadFixture(in fixturePath: String) throws -> Data {
return try Data(contentsOf: fixtureUrl(for: fixturePath))
}
func fixtureUrl(for fixturePath: String) -> URL {
return FixtureManager.fixturesDirectory.appendingPathComponent(fixturePath)
}
func save<T: Encodable>(object: T, in fixturePath: String) throws {
let data = try JSONEncoder().encode(object)
try data.write(to: fixtureUrl(for: fixturePath))
}
func loadFixture<T: Decodable>(in fixturePath: String, as decodableType: T.Type) throws -> T {
let data = try loadFixture(in: fixturePath)
return try JSONDecoder().decode(decodableType, from: data)
}
}
Creates unique "file name" form url including two previous folders
func createFileNameFromURL (colorUrl: URL) -> String {
var arrayFolders = colorUrl.pathComponents
// -3 because last element from url is "file name" and 2 previous are folders on server
let indx = arrayFolders.count - 3
var fileName = ""
switch indx{
case 0...:
fileName = arrayFolders[indx] + arrayFolders[indx+1] + arrayFolders[indx+2]
case -1:
fileName = arrayFolders[indx+1] + arrayFolders[indx+2]
case -2:
fileName = arrayFolders[indx+2]
default:
break
}
return fileName
}