In iOS, how do I parse a JSON string into an object - ios

I come from Android dev, so sorry if I'm missing obvious iOS concepts here.
I have a JSON feed that looks like:
{"directory":[{"id":0,"fName":"...","lName":"...","title":"...","dept":"...","bld":"...","room":"...","email":"...","phone":"..."},{"id":1,"fName":"...","lName":"...","title":"...","dept":"...","bld":"...","room":"...","email":"...","phone":"..."}]}
Then, I have a Staff.h and .m with a class with properties to match it (id, fName, lName) ect.
I've been working at this for hours, but I can't seem to parse the JSON string to an array of Staff objects. The end goal is to get them into Core Data, so any advice would be nice.
Tutorials I've read haven't shown how to work with a JSON string in the form of {"directory":[{...}]} I had no problem doing this in my Android app, but I'm out of ideas here for iOS (6) in objective-c.
Thanks for reading.

You can do it like
NSDictionary *json = [NSJSONSerialization JSONObjectWithData:responseObject options:0 error:&error];//response object is your response from server as NSData
if ([json isKindOfClass:[NSDictionary class]]){ //Added instrospection as suggested in comment.
NSArray *yourStaffDictionaryArray = json[#"directory"];
if ([yourStaffDictionaryArray isKindOfClass:[NSArray class]]){//Added instrospection as suggested in comment.
for (NSDictionary *dictionary in yourStaffDictionaryArray) {
Staff *staff = [[Staff alloc] init];
staff.id = [[dictionary objectForKey:#"id"] integerValue];
staff.fname = [dictionary objectForKey:#"fName"];
staff.lname = [dictionary objectForKey:#"lName"];
//Do this for all property
[yourArray addObject:staff];
}
}
}

Use: NSJSONSerialization
You use the NSJSONSerialization class to convert JSON to Foundation
objects and convert Foundation objects to JSON.
An object that may be converted to JSON must have the following properties:
The top level object is an NSArray or NSDictionary.
All objects are instances of NSString, NSNumber, NSArray, NSDictionary, or NSNull.
All dictionary keys are instances of NSString.
Numbers are not NaN or infinity.
You will get NSDictionary then you can parse (create) it to your object and then use it in CoreData.

Use following code:
NSDictionary *dictionary = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&error];
This will covert json data onto NSDictionary, which is similar to hashmap on android. I think this will help you. :)

you can use NSJSonSerialisation or AFNetworking library. Here is the example of AFNetworking to parse json response
AFHTTPRequestOperationManager *manager = [AFHTTPRequestOperationManager manager];
[manager GET:#"http://example.com/resources.json" parameters:nil success:^(AFHTTPRequestOperation *operation, id responseObject) {
NSLog(#"JSON: %#", responseObject);
NSDictionary *json = (NSDictionary *)responseObject;
NSArray *staffArray = json[#"directory"];
[staffArray enumerateObjectsUsingBlock:^(id obj, NSUInteger index, BOOL *stop){
Staff *staff = [[Staff alloc] init];
staff.id = [[obj objectForKey:#"id"] integerValue];
staff.fname = [obj objectForKey:#"fName"];
staff.lname = [obj objectForKey:#"lName"];
//add data to new array to store details
[detailsArray addObect:staff);
} ];
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
NSLog(#"Error: %#", error);
}];
then use Core Data framework to store data.

I would take a look at RestKit. It provides object-mapping and CoreData backed storage.

For this, you can SBJSON framework.
You have to convert the response string into an NSDictionary like
NSString *responseString = [[NSString alloc]initWithData:responseData encoding:NSUTF8StringEncoding];
NSDictionary *dic = [responseString JSONValue];
Now you can create an object for Staff class.
Staff *staff = [[Staff alloc]init];
Then you can store values in this object like
staff.firstname = [[[dic objectForKey:#"directory"] objectAtIndex:0] objectForKey:#"fName"];
Now you can pass this single object to other classes

You can use the handmade solution proposed by #janak-nirmal, or use a library like jastor, https://github.com/elado/jastor, it doesn't make much difference.
I warn you against Restkit, because the ratio benefits-vs-pain is very low, in my opinion.
Moreover, it could be as use a tank to kill a fly in your scenario.

Related

Single object json parse - what am I doing wrong?

This has got to be something obvious that I am doing wrong. I have been banging my head against a wall trying to figure out what is going on. I already have this json parsing done in the android version of my app, now trying to parse this simple json in xcode and can't get it done.
NSError *myError = nil;
NSDictionary *res = [NSJSONSerialization JSONObjectWithData:self.responseData options:kNilOptions error:&myError];
NSLog([res objectForKey:#"Date"]);
This code get me the "unrecognized selector sent to instance" error.
Here is the json data and you can see Date is one of the objects:
[{"Date":"2016-06-17T22:56:33.0811255-05:00"}]
Thanks in advance for any help on this issue. I've tried to simplify this post, but if more info is needed I will try and quickly provide.
http://i.stack.imgur.com/Y5fsT.png
JSONObjectWithData is returning an array of dictionaries and not a dictionary. Your print out of the raw JSON confirms this:
[{"Date":"2016-06-17T22:56:33.0811255-05:00"}] // This is an array
However you're attempting to treat that response object like a dictionary. In doing so you're calling a dictionary method (objectForKey:) on an array. This results in a crash. Try something like this:
NSError *error = nil;
id responseObject = [NSJSONSerialization JSONObjectWithData:self.responseData options:kNilOptions error:&error];
if (error)
{
// Handle error
return;
}
NSLog(#"%#", responseObject);
if ([responseObject isKindOfClass:[NSArray class]])
{
NSArray *responseArray = (NSArray *)responseObject;
for (id item in responseArray)
{
NSLog(#"%#", item);
if ([item isKindOfClass:[NSDictionary class]])
{
NSDictionary *dictionary = (NSDictionary *)item;
NSString *dateString = [dictionary objectForKey:#"Date"];
NSLog(#"%#", dateString);
}
}
}
else
{
// responseObject is not an array...
}
I'm pretty sure this is because you should first set res as [NSDictionary]. Then pick the first element in that array and then get objectForKey: "Date". Normal JSON Data starts with a {, this starts with a [. Which means it's an array.
You can see it for yourself in the screenshot when it says #: 1 Element . THEN it says 1 key/value pair. The NSDictionary is inside an array.NSError
Try this code:
*myError = nil;
[NSDictionary] *res = [NSJSONSerialization JSONObjectWithData:self.responseData options:kNilOptions error:&myError];
if (res.count > 0) {
NSLog([res[0] objectForKey:#"Date"]);
}

Getting one value from JSON API in Objective-C

I'm trying to get one value from JSON. JSON is located in NSString and it looks like this:
{"coord":{"lon":-122.38,"lat":37.57},"weather":[{"id":300,"main":"Drizzle","description":"Lekka mżawka","icon":"09d"}],"base":"stations","main":{"temp":304.74,"pressure":1017,"humidity":35,"temp_min":300.15,"temp_max":307.59},"visibility":16093,"wind":{"speed":6.7,"deg":250},"clouds":{"all":75},"dt":1437346641,"sys":{"type":1,"id":478,"message":0.0615,"country":"US","sunrise":1437311022,"sunset":1437362859},"id":5357155,"name":"Hillsborough","cod":200}
I'm interested in getting "temp". How should I do that?
Assuming your JSON string was stored as a NSString named JSONString:
NSError *error;
NSDictionary *keys = [NSJSONSerialization JSONObjectWithData:[JSONString dataUsingEncoding:NSUTF8StringEncoding]
options:NSJSONReadingMutableContainers
error:&error];
NSLog(#"temp = %#", keys[#"main"][#"temp"]); // temp = 304.74
To get the main sub item in weather, which is an array with multiple items, you should point out its index to tell the selector which object in the array is the one you are looking for. In this case, it's 0:
NSLog(#"weather = %#", keys[#"weather"][0][#"main"]); // weather = Drizzle

-[__NSCFArray objectForKeyedSubscript:] error?

I'm trying to get the data from a JSON response object in my iOS app after I log in. I keep getting this error though.
Error:
'NSInvalidArgumentException', reason: '-[__NSCFArray objectForKeyedSubscript:]: unrecognized selector sent to instance 0x8fc29b0'
Here is my code for the request, I'm using AFNetworking:
self.operation = [manager GET:urlString parameters:params success:^(AFHTTPRequestOperation *operation, id responseObject) {
NSDictionary *JSON = (NSDictionary *)responseObject;
NSDictionary *user = JSON[#"user"];
NSString *token = user[#"auth_token"];
NSString *userID = user[#"id"];
// NSString *avatarURL = user[#"avatar_url"];
// weakSelf.credentialStore.avatarURL = avatarURL;
weakSelf.credentialStore.authToken = token;
weakSelf.credentialStore.userId = userID;
weakSelf.credentialStore.username = self.usernameField.text;
weakSelf.credentialStore.password = self.passwordField.text;
[SVProgressHUD dismiss];
[self dismissViewControllerAnimated:YES completion:nil];
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
if (operation.isCancelled) {
return;
}
[SVProgressHUD showErrorWithStatus:#"Login Failed"];
NSLog(#"%#", error);
}];
What the JSON response object looks like logged:
<__NSCFArray 0x8cac0b0>(
{
user = {
"auth_token" = b3a18e0fb278739649a23f0ae325fee1e29fe5d6;
email = "jack#jack.com";
id = 1;
username = jack;
};
}
)
I'm converting the array to a Dictionary using pointers like this:
EDIT: As pointed out in the comments incase anyone else stumbles across this with limited knowledge in iOS. I'm casting here not converting. See the answers for a full explanation.
NSDictionary *JSON = (NSDictionary *)responseObject;
I'm new to iOS, apologies if problem is obvious.
Thanks for any help.
The "conversion" you do is not doing any conversion, it's a cast. This simply tells the compiler to ignore the type it knows for this object and act as if it's the type you pass it.
Looking at the output you have, you don't get a dictionary back, but an array of dictionaries with a single dictionary. To get to the first dictionary you can use this instead of the cast:
NSDictionary *JSON = [responseObject objectAtIndex:0];
Note that since you get your data from a web service, you should probably also check if the contents you get are what you expect.
You say:
I'm converting the array to a Dictionary using pointers like this:
But that is not what you are doing. You are casting it, but the underlying object is still an array.
From the JSON response you can see that those JSON is constructed as an array with a single element which is a dictionary. You can get to the dictionary by calling [responseObject firstObject];. Of course, so that you don't get error going in the other direction, you should check how the input is constructed before calling any array or dictionary specific methods on the response object.
You have to convert your self but do not use casting.
Or, this is the code to detect if a json object is an array or dictionary
NSError *jsonError = nil;
id jsonObject = [NSJSONSerialization JSONObjectWithData:jsonData options:kNilOptions error:&jsonError];
if ([jsonObject isKindOfClass:[NSArray class]]) {
NSLog(#"its an array!");
NSArray *jsonArray = (NSArray *)jsonObject;
NSLog(#"jsonArray - %#",jsonArray);
}
else {
NSLog(#"its probably a dictionary");
NSDictionary *jsonDictionary = (NSDictionary *)jsonObject;
NSLog(#"jsonDictionary - %#",jsonDictionary);
}

iOS parsing a jsonDictionary

I am from php domain, and now learning ios coding. I want to make a view with one part showing user info, and a table showing friends details.
I can get the json Logged correctly.
My json looks like this:
{"Me":
{"username":"aVC",
"userID":1
},
"Friends":
[{"username":"Amm",
"userID":2
},...
]
}
Here is what I use.
NSError *error;
NSString *responseString = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];
NSDictionary *json = (NSDictionary*)[NSJSONSerialization JSONObjectWithData:responseData options:kNilOptions error:&error];
NSLog(#"jS: %#", json);
this works fine. I want to seperate the two sections (Me, and friends), and then use it to fill tables. Can someone throw some ideas?
NOTE: I am not using any frameworks. Just NSJSONSerialization.
Try adding this code after obtaining the json dictionary:
NSDictionary *me = [json objectForKey:#"Me"];
NSArray *friends = [json objectForKey:#"Friends"];
This should let you pull the information from the #"Me" and #"Friends" into separate variables.

iOS JSON Parse into NSDictionary and then NSArray with SBJson

It should be so simple but I cannot get it work.
Json response is
([{"id":"1", "x":"1", "y":"2"},{"id":2, "x":"2", "y":"4"}])
NSString *response = [request responseString];
//response is ([{"id":"1", "x":"1", "y":"2"},{"id":2, "x":"2", "y":"4"}])
SBJSON *parser = [[[SBJSON alloc] init] autorelease];
NSDictionary *jsonObject = [parser objectWithString:response error:NULL];
// jsonObject doesn't have any value here..Am I doing something wrong?
NSMutableArray Conversion = [jsonObject valueForKey:NULL];
//Even if I get the value of jsonObject. I don't know what to put for valueForKey here
Conversion shoud have two NSObjects..and each of them should have like
id:1
x:1
y:2
and
id:2
x:2
y:4
Your JSON parser will produce an NSArray from your response string, not an NSDictionary. Note that JSON parsers, including SBJSON, will return either an array object or a dictionary object, depending on the contents of the json that is being parsed.
NSArray *jsonObject = [parser objectWithString:response error:nil];
You can then access the individual items in your array (the array elements will be of type NSDictionary) and use valueForKey: to get the properties of each item.
NSDictionary *firstItem = [jsonObject objectAtIndex:0];
NSString *theID = [firstItem objectForKey:#"id"];

Resources