I have a HTTP GET request that returns either:
{"events":"Event Goes Here"}
or
{"service":"Service goes here"}
At the moment I'm writing two HTTP Get functions so that when I get to:
if let results: NSArray = jsonResult["services"] as? NSArray {
or
if let results: NSArray = jsonResult["events"] as? NSArray {
I know that Im getting the services or the events Json data.
I want to be able to streamline the HTTP Get request so that I can call in a single function:
func makeGETRequest(urlRequest: String) {
how do I read the string in json0 to be able to determine if its an event or a service?
You seem to already know how to parse the data, but are asking how you might wrap it up to avoid redundancy.
I think you are looking for something like this:
func getStuff(urlRequest:String) -> Result
where Result is an enum with associated values for your payload. Documentation can be found here
You could then call the function something like this:
switch (getStuff("someUrl")) {
case let .Events(events):
doStuffWith(events)
break
case let .Service(serviceStuff):
doStuffWith(serviceStuff)
break
}
The baseline for the form you suggest though, is that if you want to use a common function, you have to return a multiplexed type. Your other option, is for it to call type specific handler functions / closures for each of the possible types, so you are not relying on the return type, but are reacting to the results with further calls such that all processing is done by the time that your getStuff() function returns.
As far as actual parsing goes, you would just use a series of if-let unwrappings to check for which result you got.
I don't do Swift, so translate the following ObjC to Swift and it may work, this is just a snippet, but this won't work because json[#"XXX"] requires an NSDitionary
- (id)initWithJson:(NSArray *)json
{
NSArray* object = json[#"events"] ?: json[#"service"];
self = [super initWithJson:object];
if (self == nil)
{
return nil;
}
//do work
return self;
}
so, you should try to reform your JSON packet that you get from the server, I can't image it being set up in a way that it doesn't send you a dictionary first that you must then parse to an array.
or something like this:
NSString * valueYouWant = json[#"events"] ?: json[#"service"];
using this:
-(NSString*)getValue:(NSDictionary*)json
{
NSString * valueYouWant = json[#"events"] ?: json[#"service"];
return valueYouWant;
}
you would call this by doing sending your "response object" from the server to the NSString method above
Related
I am trying to mock Apollo Queries using its init. It pretty much is taking in a dictionary to build the object up.
public init(unsafeResultMap: [String: Any]) {
self.resultMap = unsafeResultMap
}
So, I have decided to create Mock objects that have the same properties of the query objects while being Encodable (So we get the free JSON conversion, which can be represented as a string version dictionary).
For example:
class MockAnimalObject: Encodable {
let teeth: MockTeethObject
init(teeth: MockTeethObject) {
self.teeth = teeth
}
}
class MockTeethObject: Encodable {
let numberOfTeeth: Int
let dateOfTeethCreation: Date
init (numberOfTeeth: Int, dateOfTeethCreation: Date) {
self.numberOfTeeth = numberOfTeeth
self.dateOfTeethCreation = dateOfTeethCreation
}
}
The problem is, the Apollo conversion checks the types during the result map, which in our case is a string of [String: Encodable].
And this is where the Date encodable becomes a problem.
/// This property is auto-generated and not feasible to be edited
/// Teeth date for these teeth
public var teethCreationDate: Date {
get {
// This is the problem. resultMap["teethCreationDate"] is never going to be a Date object since it is encoded.
return resultMap["teethCreationDate"]! as! Date
}
set {
resultMap.updateValue(newValue, forKey: "teethCreationDate")
}
}
So, I am wondering if it is possible to override the encoder to manually set the date value as a custom type.
var container = encoder.singleValueContainer()
try container.encode(date) as Date // Something where I force it to be a non-encodable object
JSON has nothing to do with this. JSON is not any kind of dictionary. It's a serialization format. But you don't want a serialization format. You want to convert types to an Apollo ResultMap, which is [String: Any?]. What you want is a "ResultMapEncoder," not a JSONEncoder.
That's definitely possible. It's just an obnoxious amount of code because Encoder is such a pain to conform to. My first pass is a bit over 600 lines. I could probably strip it down more and it's barely tested, so I don't know if this code works in all (or even most) cases, but it's a start and shows how you would attack this problem.
The starting point is the source code for JSONEncoder. Like sculpture, you start with a giant block of material, and keep removing everything that doesn't look like what you want. Again, this is very, very lightly tested. It basically does what you describe in your question, and not much else is tested.
let animal = MockAnimalObject(teeth: MockTeethObject(numberOfTeeth: 10,
dateOfTeethCreation: .now))
let result = try AnyEncoder().encode(animal)
print(result)
//["teeth": Optional(["dateOfTeethCreation": Optional(2022-08-12 18:35:27 +0000),
// "numberOfTeeth": Optional(10)])]
The key changes, and where you'd want to explore further to make this work the way you want, are:
Gets rid of all configuration and auto-conversions (like snake case)
Handles the "special cases" (Date, Decimal, [String: Encodable]) by just returning them. See wrapEncodable and wrapUntyped
If you want [String: Any] rather than [String: Any?] (which is what ResultMap is), then you can tweak the types a bit. The only tricky piece is you would need to store something like nil as Any? as Any in order to encode nil (or you could encode NSNull, or you could just not encode it at all if you wanted).
Note that this actually returns Any, since it can't know that the top level encodes an object. So you'll need to as? cast it to [String: Any?].
To your question about using Mirror, the good thing about Mirror is that the code is short. The bad thing is that mirror is very slow. So it depends on how important that is. Not everything has the mirror you expect, however. For your purposes, Date has a "struct-like" Mirror, so you have to special-case it. But it's not that hard to write the code. Something like this:
func resultMap(from object: Any) -> Any {
// First handle special cases that aren't what they seem
if object is Date || object is Decimal {
return object
}
let mirror = Mirror(reflecting: object)
switch mirror.displayStyle {
case .some(.struct), .some(.class), .some(.dictionary):
var keyValues: [String: Any] = [:]
for child in mirror.children {
if let label = child.label {
keyValues[label] = resultMap(from: child.value)
}
}
return keyValues
case .some(.collection):
var values: [Any] = []
for child in mirror.children {
values.append(resultMap(from: child.value))
}
return values
default:
return object
}
}
let animal = MockAnimalObject(teeth: MockTeethObject(numberOfTeeth: 10, dateOfTeethCreation: .now))
let result = resultMap(from: animal)
print(result)
// ["teeth": ["dateOfTeethCreation": 2022-08-12 21:08:11 +0000, "numberOfTeeth": 10]]
This time I didn't bother with Any?, but you could probably expand it that way if you needed. You'd need to decide what you'd want to do about enums, tuples, and anything else you'd want to handle specially, but it's pretty flexible. Just slow.
As pointed out in comments, JSON (Javascript object notation) is universal format and is not anyhow related to Date object in Swift after it is encoded. Therefore somewhere in the flow you need to make it String Double or some other object type that can be encoded to JSON. Anyway, if you want to make encoding Date to be easier you can take hold of some native JSONEncoder functions, such as folowing:
let encoder = JSONEncoder()
encoder.dateEncodingStrategy = .iso8601
I can make a Facebook SDK Graph Request to get a user's likes, but I'm having trouble taking the returned values and storing one of the keys in an array of Strings. The request returns an NSDictionary of keys/values. Then, using objectForKey I can get the data key which returns what I want: the id and name of the "liked" page on Facebook.
Data returns elements like this:
{
id = 486379781543416;
name = "Star Wars Movies";
},
I specifically want only the "name" of all of these objects and to throw them into an array [String]. I tried to loop through the objects but I'm getting error ambiguous use of subscript. Here's the relevant code:
request.startWithCompletionHandler{(connection:FBSDKGraphRequestConnection!, result:AnyObject!, error:NSError!) -> Void in
let resultdict = result as! NSDictionary
let likes = resultdict.objectForKey("data") as! NSArray
print("Found \(likes.count) likes")
print(likes)
for object in likes{
let name = object["name"] as! String //error: ambiguous use of subsript
print(name)
}
}
After doing some research it looks like the issue is with the NSArray and that I should instead use Swift data types. I tried casting it to a Swift array but I got different errors.
What's the best way to handle this error?
Thanks!
update: Here is what the facebook API request returns:
{
data = (
{
id = 111276025563005;
name = "Star Wars (film)";
},
{
id = 115061321839188;
name = "Return of the Jedi";
}
);
paging = {
cursors = {
after = MTE1MDYxMzIxODM5MTg4;
before = Mjc0NzYzODk2MTg4NjY5;
};
next = "https://graph.facebook.com/v2.5/10155262562690368/likes?access_token=<redacted>";
};
}
You should always use the native Swift collection types wherever possible as NSArray and NSDictionary are really type-inspecific, and therefore can easily trigger "ambiguous use of subscript" errors.
You'll also want to avoid force down-casting, in case you receive data that's in the wrong format, or no data at all. This situation would be more elegantly handled with a guard, in order to prevent a crash. If your program depends on the force down-casting succeeding, and therefore should crash – then you can always call fatalError in the guard, with a descriptive error message in order to assist you in debugging the problem.
If I understand your data structure correctly, the request returns an AnyObject that should be a [String:AnyObject] (A dictionary of strings to any objects). In the case of the "data" key, the AnyObject value is then a [[String:AnyObject]] (An array of dictionaries of strings to any objects).
Therefore you'll want to do your casting in two stages. First, using a conditional downcast on your result to cast it as a [String:AnyObject]. If this fails, then the else clause of the guard will be executed and the code will return. You'll then want to get out your "data" value (your 'likes' array), and conditionally downcast it to a [[String:AnyObject]]. Both of these statements will handle the possibility of resultDict or resultDict["data"] being nil.
guard let resultDict = result as? [String:AnyObject] else {return}
guard let likes = resultDict["data"] as? [[String:AnyObject]] else {return}
You can put whatever error handling logic you want in the brackets of these statements to handle cases in which the results dictionary doesn't exist, was the wrong format, or there wasn't a 'likes' array in it.
You can then get an array of 'like' names through using flatMap.
let likeNames = likes.flatMap{$0["name"] as? String}
This will create an array of the like names of each dictionary – if the like names don't exist or aren't strings, then they won't be added. Because the compiler knows for certain that likes is a [[String:AnyObject]] – there's no ambiguity in subscripting its elements.
If you want a more general approach such as you're doing in your question, you can use a guard statement within a for loop.
for object in likes {
guard let name = object["name"] as? String else {continue}
print(name)
}
Again, you can put whatever error handling you wish in the brackets of the guard.
I have JSONString from api as bellow:
[JSONString from api]
But after I read in iOS from Alamofire the order of the JSONString is not correct as api:
[JSON After read in iOS]
How can I keep the JSON format the same order as api?
As explained by #Nimit, JSON format represented in your callback and the API response is of least concern. What you need to care about is that when you are accessing the values from the response, the KEY should be same as seen in the API. No mismatch, not even of the case-sensitive letter, or you will always get the NIL in the response.
To explain it better to you with the use of Alamofire, let's me show you one example:
let APIURL = "https://api.yoururl.com"
Alamofire.request(.GET, APIURL , headers: headers) .responseJSON { response in
let value = response.result.value!
let JSONRes = JSON(value)
let KLValue = JSONRes["Kuala Lumpur"].int!
print(KLValue) //Or call a function to handle the callback
}
Here I am using SwiftyJSON for JSON. In the end, all you want to do is get the data out of the associated keys in the JSON response, no need to worry about how they have been formatted, or what's the order of Keys in the response - most of the time you will get the same as in the API - but in case it changes, need not to worry.
On the another front, to be sure that nothing happens to your app when JSON fields are nil, always put an if-let like this:
if let valueFromJSON = JSONRes["Kuala Lumpur"].string {
someVariable = valueFromJSON
} else {
someVariable = "No Value"
}
Thanks!
You can't do it, unless you write your own JSON parser. Any self-respecting JSON library won't guarantee you the order, if it wants to conform to the JSON spec.
From the definition of the JSON object:
the NSDictionary class represents an unordered collection of objects;
however, they associate each value with a key, which acts like a label
for the value. This is useful for modeling relationships between pairs
of objects.
If you have a jsonObject, such as data, then you can convert to json string like this:
let jsonString = JSONSerialization.data(withJSONObject: data,
options: JSONSerialization.WritingOptions.sortedKeys)
when you use sortedKeys option, the json will be specifies that the output sorts keys in lexicographic order.
This is what I have
let kind = //This returns one of the cases with it corresponding arguments
if kind == .didChangeValue(value: nil) {
//my Stuff
}
this is what I want:
if kind == .didChangeValue {
//my Stuff
}
Notice that:
This is happening because my enum has arguments, I already implemented how they should compare with each other and the value has no value to me.
So, I'm trying to get it to look more swifty and less like a RAW HACK
You can check an enumeration value with pattern matching:
if case .didChangeValue = kind {
// ...
}
In a delegate method, I get back a ‘results’ array of a custom object type, and I want to loop through the array elements.
I do the following now, and this works
for result in results {
if result is XYZClass {
//This Works!
}
}
Is there a way to type cast the objects in the for-loop to avoid writing two lines? Does swift permit this? Used to get this done fairly easily in Objective - C
for (XYZClass *result in results) {
}
However, I have not been successful in Swift. I’ve tried explicit-cast with no luck.
for result as XYZClass in results {
//ERROR: Expected ‘;’ in ‘for’ statements
}
for result:AGSGPParameterValue in results {
/* ERROR: This prompts down cast as
for result:AGSGPParameterValue in results as AGSGPParameterValue { }
which in turn errors again “Type XYZClass does not conform to Sequence Type”
*/
}
Any help is appreciated
Try this:
for result in results as [XYZClass] {
// Do stuff to result
}
Depending on how you are using the for loop it may be instead preferable to use compactMap (or flatMap if you are before Swift 4.1) to map your objects into a new array:
let onlyXyzResults: [XYZClass] = results.compactMap { $0 as? XYZClass }
Now you have an array XYZClass objects only, with all other object types removed.