I'm running the following in a playground (I've tested in Xcode 7.3.1 as well as Xcode 8.1 and see the same behavior):
import UIKit
let key: String = "some_key"
let value: String = "some_value"
UIPasteboard.general.items = [[key: value]]
let item = UIPasteboard.general.items.first
if let item = UIPasteboard.general.items.first {
switch item[key] {
case let x as String:
print("This is expected")
case let x as Any:
type(of: x)
print("This is unexpected")
default:
print("This is unexpected")
}
} else {
print("This is unexpected")
}
And I notice that the String that I put into the pasteboard actually gets bridged back out as NSConcreteMutableData.
My questions are the following:
Is this caused by an internal UIPasteboard implementation (i.e. explicitly converting from NSString to NSConcreteMutableData), or is this standard ObjC-Swift bridging behavior?
How can I work around this to store custom key/value pairs in UIPasteboard?
Here's what this looks like in a playground, for easy reference:
The Data you get for item[key] is simply the UTF-8 encoded value for the string.
If you add the following case, you will see that:
case let x as Data:
let str = String(data: x, encoding: .utf8)
print("str = \(str)")
The cause of the confusion is that the keys used by the items property are UTIs, not random keys. If you change your key to public.text then your code will work as expected.
Normally, you would not put a string on the pasteboard using the items property. You would use the string property to read and write the value.
UIPasteboard.general.string = "Hello"
let aStr = UIPasteboard.general.string
print("aStr = \(aStr)")
Doing this avoids the need to specify a UTI and it avoids replacing all existing items on the pasteboard.
Related
First off, what do we call a dictionary with a format like this in iOS?
(
{
name = "Apple";
value = "fruit-1";
},
{
name = "Banana";
value = "fruit-2";
}
)
And for my main question. I somehow need to format a string of JSON, like this:
[{"name":"Apple","value":"fruit-1"},{"name":"Banana","value":"fruit-2"}]
into whatever that format is called (of the string above).
For context, the existing approach of my project uses CoreData where the Server response (which uses the mystery format above) gets saved locally as a String, and I want to follow that format.
EDIT: for more context, I really need to just get the first format into the database because a module of a project was built to read the data with that format (e.g. make use of NSString.propertyList()).
Using a library called ios hierarchy viewer, I can see the saved object in the device.
Original format, server json to db (core data) in Objective-C:
What I've been trying to do in Swift, server json to local using JSONSerialization:
First off, what do we call a dictionary with a format like this in iOS?
According to the documentation of NSString.propertyList(), that's a "text representation of a property list".
It's a wonky, non-standard pretty-printing obtained by calling NSArray.description or NSDictionary.description.
Here's an example that shows a round-trip of data:
// The opening `{` indentation is fucky, but that's how it's generated.
let inputPropertyList = """
(
{
name = "Apple";
value = "fruit-1";
},
{
name = "Banana";
value = "fruit-2";
}
)
"""
// The result is an `Any` because we don't know if the root structure
// of the property list is an array or a dictionary
let deserialized: Any = inputPropertyList.propertyList()
// If you want the description in the same format, you need to cast to
// Foundation.NSArray or Foundation.NSDictionary.
// Swift.Array and Swift.Dictionary have a different description format.
let nsDict = deserialized as! NSArray
let roundTrippedPropertyList = nsDict.description
print(roundTrippedPropertyList)
assert(roundTrippedPropertyList == inputPropertyList)
The second format you show is what you get when you display an object in the debug console. That's the output of the object's description property. It isn't a "JSON string", exactly.
If you want to convert your objets to a true JSON string, see below.
As Alexander pointed out, the first string in your question is the output from NSString's propertyList() function. The format looks quite similar to "pretty-printed" JSON, but it's different enough that it it won't work that way.
The `propertyList() function is a debugging-only function, and I don't know of an existing way to parse that back into objects. If that is the string that's being sent by your server, your server is broken. If that's what you see in core data when you log the contents of a field, it's probably a misunderstanding on your part.
To convert an object to pretty JSON, see this answer, where I created an extension to the Encodable format that implements a property "prettyJSON":
extension Encodable {
var prettyJSON: String {
let encoder = JSONEncoder()
encoder.outputFormatting = .prettyPrinted
guard let data = try? encoder.encode(self),
let output = String(data: data, encoding: .utf8)
else { return "Error converting \(self) to JSON string" }
return output
}
}
That should work for any object that supports the Encodable protocol. (And your object should.)
I’m coding Swift for iOS 11, and in some context (described in part 2) I end up with a variable of type String. However, when examining the variable in Xcode’s debugger the type is shown as _PFEncodedString (which I have read elsewhere is an internal subclass of String). For some reason (described below, but not directly related to the first part of my question) I want to transform the _PFEncodedString variable to a plain String variable. The only way I’ve found to do that is as follows:
var attributeName : String
// ... attributeName is assigned a value and ends up being _PFEncodedString
let data = attributeName.data(using: String.Encoding.utf8)!
let plainName = String(data: data, encoding: String.Encoding.utf8)! // this is type String not _PFEncodedString
The first part of my question is: Is this conversion safe or is there is simpler or better way to do it?
Part 2. For the second part of my question I will first describe the context where the above becomes an issue. I’m using Core Data and want to export attribute names (and values) to JSON. Using reflection I can find Core Data entity names and find the attribute names that should be exported to JSON. The problem is that when I use JSONEncoder with this data, the generated JSON contains Chinese characters whereas the Core Data model attribute names do not. I have found that JSONEncoder produces partly Chinese output when Strings in the exported object is of type _PFEncodedString, but works fine when handling "plain" String types. Therefore the first part of my questions.
Here is code that illustrates the problem, boiled down to a near minimum. QPTVideo is a subclass of NSManagedObject with two attributes ‘qaUUID’ and ‘thumbnailData’.
// First define a struct to be used with JSONEncoder
struct AttributeForJSON : Codable {
var name : String
}
let entityDescription = QPTVideo.entity()
let attributes = entityDescription.attributesByName // this is an array of (key: String, value: NSAttributeDescription).
var allAttributes : [AttributeForJSON] = [] // this will be an array of all the attribute names for export to JSON.
for attribute in attributes {
let attributeName = attribute.key // NOTE: debugger shows this as: attributeName String class name = _PFEncodedString
let aj = AttributeForJSON(name: attributeName)
print(aj.name) // this works just fine, printing “qaUUID” or “thumbnailData”
allAttributes.append(aj) // when exported, the attribute names look nothing like they should, containing Chinese characters.
// now use the work-around from first part of my question:
let data = attributeName.data(using: String.Encoding.utf8)!
let plainName = String(data: data, encoding: String.Encoding.utf8)! // NOTE: debugger shows this as: plainName String "thumbnailData"
let ajplain = AttributeForJSON(name: plainName)
allAttributes.append(ajplain) // when exported, the attribute names are correct.
}
// the rest is just use of JSONEncoder to generate the JSON
let encoder = JSONEncoder()
encoder.outputFormatting = .prettyPrinted
do {
let data = try encoder.encode(allAttributes)
try data.write(to: URL(fileURLWithPath: “/Users/someone/so.json"), options: Data.WritingOptions.atomic)
} catch {
print(error.localizedDescription)
}
The exported JSON looks like this (where I would have expected both of the first two name values to be "qaUUID", and the next two to be "thumbnailData"):
[
{
"name" : "慱啕䑉\u0000戨্"
},
{
"name" : "qaUUID"
},
{
"name" : "桴浵湢楡䑬瑡a\u0000戨্\u0001\u0000\u0000"
},
{
"name" : "thumbnailData"
}
]
So, my here question is: Why do I get Chinese characters? What am I doing wrong in how I use the Core Data reflection API and/or JSONEncoder? How do I do this without resorting to the work-around from the first part of my question?
I have been trying to parse a CSV file forever and I am almost there. I have gotten it to a multi-dimensional array of strings using this code:
let path = Bundle.main.url(forResource: "BaseballSimStats", withExtension: "csv")
var file = String()
do {
file = try String(contentsOf: path!)
print(file)
} catch {
print(error)
}
let stringarray = file.components(separatedBy: "\n").map{ $0.components(separatedBy: ",") }
Now the last step is to turn it into a Double. I am using this code:
probs = Double[[stringarray]]
I get an error saying that the type has no subscript errors. I get rid of the subscript references and the error goes away. Why is this error here and how can I get rid of it? Thanks!
I used .map() to map the String into a Double, this should work for nested array
var strArray = [["1.00000","1.10000"],["2.00000","2.10000"]]
var doubleArray = strArray.map { (arr: Array) -> Array<Any> in
return arr.map({ (value: String) -> Double in
return Double(value)!
})
}
print(strArray)
print(doubleArray)
I am not sure if the double map was needed.
I am not a swift guru but this code should help you achieve what you want..
I'm not familiar with Double[[stringarray]] syntax so I don't know how that's supposed to work. I do know you can't just cast between array types.
The simplest way is probably to wrap the innermost call with Double.init():
file.components(separatedBy: "\n").map{ $0.components(separatedBy: ",").map { Double($0)! }}
Of course, there's a bit more to CSV than just splitting on commas and assuming everything is a valid number, so I'd highly recommend using an existing CSV parsing library for any real data.
I am inserting an Array into my database as a String and after fetching it I want it to convert it again to Array. So that I can fetch my values again and I can do next operation.
Here below is my array inserting into database(TestQuestion) as a String:
let testQuestionModel : TestQuestion = NSEntityDescription.insertNewObject(forEntityName: "TestQuestion", into: AppDelegate.getContext()) as! TestQuestion
testQuestionModel.optionsArray = "\(question["options"] as! NSArray)"
Example: String Array I am getting from Database
(\n \"Rahul Abhyankar\",\n \"Pinkesh Shah\",\n \"Ramanan
Ganesan\",\n \"Dr. Marya Wani\",\n \"\",\n \"\"\n)".
Here is 4 options you can see this is my string after fetching from Database.
1) Rahul Abhyankar.
2) Pinkesh Shah.
3) Ramanan Ganesan.
4) Dr. Marya Wani.
Now how can I convert it into array?
I tried some methods.
let arr = NSArray(object: quetion.optionsArray!).
But I am getting only one object. How can I get my array values same as previous from this string array?
I don't know about the actual type of the "option" in your code, so I set up a fake Elem struct to represent it. The remaining logic is independent of the type as long as you provide a conversion logic to and from String.
struct Elem {
// let's say this is your element type in your array
let foo: Int;
}
extension Elem: CustomStringConvertible {
var description: String {
// provide a logic to convert your element to string
return "\(foo)";
}
}
let arrayToSave = [
Elem(foo: 1),
Elem(foo: 2),
Elem(foo: 3)
]
extension Elem {
init(string: String) {
// provide a function to construct your element type from a string
self.init(foo: Int(string)!)
}
}
let stringToSave = arrayToSave.map { $0.description }.joined(separator: "|")
// save this string
// at some point retrieve it from database, which hopefully same as the saved one
let retrivedString = stringToSave;
let retrivedArray = retrivedString.split(separator: "|").map { Elem(string: String($0)) }
print(retrivedArray) // [1, 2, 3]
Here below is my array inserting into database (TestQuestion) as a
String :
let testQuestionModel : TestQuestion = NSEntityDescription.insertNewObject(forEntityName: "TestQuestion", into: AppDelegate.getContext()) as! TestQuestion
testQuestionModel.optionsArray = "\(question["options"] as! NSArray)"
No, and No.
You are using -description method of an array to save it. Clearly no.
What's wrong? Apple can't affirm that in next OS release, it won't add an extra character. In some more complex cases, it's added <NSArray <0x address> or stuff similar like that.
Suggestion 1:
Modify your entity to have an ARRAY (or usually a Set) of String.
Learn about Core-Data relationship (but that's clearly a DataBase basic knownledge). A relationship one to many should be the thing to do.You could even keep in memory what were the choices, by adding for creating the entity Options, with a String property name (name of the option), another one boolean isChecked, etc.
Suggestion 2:
If you have a limited number of options (like says one to 5), add 5 options string to your entity, and iterate to set them
testQuestionModel.option1 = question["option"][0]
testQuestionModel.option2 = question["option"][1] (if it's of course not out of range for the array)
...
Suggestion 3:
Not really recommended (in my opinion it's missing the whole advantage of the database, especially fetch and predicates, on previous sample you could fetched easily which options were checked), but if you still want to save them as a String, save them as JSON (ie. stringified).
In pseudo code (I'm not sure about the exact syntax, there are no fail safe like try/catch, optional/wrapping):
let options = questions["options"] as [String]
let jsonData = JSONSerialization.data(withJSONObject: (question["options"], options:[])
let jsonString = String.init(data:jsonData encoding:.utf8)
To retrieve them:
let options = JSONSerialization.jsonObject(with data: myJSONString.data(encoding:.utf8), options:[]) as [String]
done using Library SwiftyJSON.
if let dataFromString = yourString?.data(using: String.Encoding.utf8, allowLossyConversion: false) {
do{
let json = try JSON(data: dataFromString)
print(json)
let arrayValue = json.rawValue as! NSArray
print(arrayValue)
} catch{
print(error.localizedDescription)
}
}
Source: https://github.com/SwiftyJSON/SwiftyJSON
I'm creating an app that should retrieve some JSON from a database.
This is how my JSON looks:
[{"id":"1","longitude":"10","latitude":"10","visibility":"5","timestampAdded":"2015-10-01 15:01:39"},{"id":"2","longitude":"15","latitude":"15","visibility":"5","timestampAdded":"2015-10-01 15:06:25"}]
And this is the code i use:
if let jsonResult = JSON as? Array<Dictionary<String,String>> {
let longitudeValue = jsonResult[0]["longitude"]
let latitudeValue = jsonResult[0]["latitude"]
let visibilityValue = jsonResult[0]["visibility"]
print(longitudeValue!)
print(latitudeValue!)
print(visibilityValue!)
}
As you can see it only gets the first chunk from the JSON and if there are no JSON at all it will crash, but if i want it to count the amount and make an array out of it like this:
var longitudeArray = [10, 15]
var latitudeArray = [10, 15]
And so on...
I also need this to be apple watch compatible so i can't use SwiftyJSON.
What do i do? I really hope you can help me!
Thanks.
SOLVED!
Problems was solved by "Eric D."
This is the code:
do {
if let url = NSURL(string: "YOU URL HERE"),
let data = NSData(contentsOfURL: url),
let jsonResult = try NSJSONSerialization.JSONObjectWithData(data, options: []) as? [[String:AnyObject]] {
print(jsonResult)
let longitudeArray = jsonResult.flatMap { $0["longitude"] as? String }
let latitudeArray = jsonResult.flatMap { $0["latitude"] as? String }
print(longitudeArray)
print(latitudeArray)
}
} catch let error as NSError {
print(error.description)
}
Thank you soo much Eric!! :-)
You could use flatMap to get an array of your elements:
let longitudeArray = jsonResult.flatMap { $0["longitude"] as? String }
let latitudeArray = jsonResult.flatMap { $0["latitude"] as? String }
etc.
flatMap is like map but unwraps optionals, which is adequate because we need to safely cast the type of the object we get from each dictionary in the json array.
$0 represents the object in the current iteration of flatMap of the array it's applied to.
If you're currently using SwiftyJSON, then that would be:
let longitudeArray = jsonResult.flatMap { $1["longitude"].string }
let latitudeArray = jsonResult.flatMap { $1["latitude"].string }
because .string is SwiftyJSON's optional String value getter.
But as you said, you don't want to use it (anymore), so you need to use NSJSONSerialization to decode your JSON data, there's plenty of examples on the Web and on SO. Then you will be able to use my original answer.
You're already getting an array with all of the elements (not just the first one. you're simply only accessing the first one). jsonResult is an array of dictionaries. Each dictionary (in this case, based on the json you provided) contains these elements: id, longitude, latitude, visibility and timestampAdded. In order to access each of them, you can simply loop over jsonResult and access the i'th element (and not always the 0 element). This will also prevent the crash you're experiencing with the json is blank or invalid (since you'll only be going over the valid elements in jsonResult.
This will give you the flexibility to create the custom arrays you wish to create (in order to create an array of all of the longitudes, for example, you will simply add that element to the new array while looping over jsonResult). However, if you'd like to save yourself the trouble of manually building these arrays and assuming you have control over the json structure, I would recommend changing the received json to the relevant structure (a dictionary or arrays instead of an array of dictionaries), so it would better fit your needs and provide you the results in the relevant format right "out of the box".