New to Xcode and obj-c.
Is it possible to sort through data structures in the console like you with JavaScript?
-(void)fetchInfo
{
NSURL *url = [NSURL URLWithString:#"http://someurl"];
NSData *jsonResults = [NSData dataWithContentsOfURL:url];
NSDictionary *dictionary = [NSJSONSerialization JSONObjectWithData:jsonResults
options:0
error:NULL];
NSLog(#"CitiBike Results = %#", dictionary);
}
The results are logged, but I now want to play with the returned dictionary
If you make a mutable copy, you can fiddle with that in the console
NSMutableDictionary *mutableDictionary = [dictionary mutableCopy];
then
p mutableDictionary[#"key"] = #"Hello, World!"
EDIT: you can also store it in a convenience variable in lldb like
expr NSMutableDictionary *$md = mutableDictionary
so that if it goes out of scope, as long as it's alive, you can still access it in the debugger like
p $md[#"key"] = #"Convenience!"
Related
Receiving the following error. I believe it has to do with the NSDictionary in the results of JSON array. I.e. NSDictionary within an NSDictionary maybe?
Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFString objectForKey:]: unrecognized selector sent to instance 0x7f9298554560'
This is the JSON service when called. This is printed directly out of XCode but it looks clean to me.
Printing description of self->metArray:
{
weatherObservation = {
ICAO = YBBN;
clouds = "few clouds";
cloudsCode = FEW;
countryCode = AU;
datetime = "2014-11-24 03:00:00";
dewPoint = 20;
elevation = 5;
hectoPascAltimeter = 1014;
humidity = 61;
lat = "-27.38333333333333";
lng = "153.1333333333333";
observation = "YBBN 240300Z 02019KT 9999 FEW029 SCT250 28/20 Q1014";
stationName = "Brisbane Airport M. O";
temperature = 28;
weatherCondition = "n/a";
windDirection = 20;
windSpeed = 19;
};
}
This is the code that invokes the JSON service.
-(void)getMetar{
// NSString *location = #"YBBN";
NSString * const metarUrl =#"http://api.geonames.org/weatherIcaoJSON?ICAO=YBBN&username=demo";
NSURL *url2 = [NSURL URLWithString:metarUrl];
NSData *data2 = [NSData dataWithContentsOfURL:url2];
metArray = [NSJSONSerialization JSONObjectWithData:data2 options:kNilOptions error:nil];
//Create an NSDictionary for the weather data to be stored.
NSDictionary *metarJson = [NSJSONSerialization JSONObjectWithData:data2 options:kNilOptions error:nil];
//Loop through the JSON array
NSArray *currentMetarArray = metarJson[#"weatherObservation"];
//set up array and json call
metarArray = [[NSMutableArray alloc]init];
for (NSDictionary *metaritem in currentMetarArray)
{
//create our object
NSString *nClouds = [metaritem objectForKey:#"clouds"];
NSString *nObservation = [metaritem objectForKey:#"observation"];
//Add the object to our animal array
[metarArray addObject:[[metar alloc]initWithclouds:(nClouds) andobservation:nObservation]];
}
}
It looks okay to me but maybe that is because I have been looking at it for hours.
Any ideas?
NSArray *currentMetarArray = metarJson[#"weatherObservation"];
for (NSDictionary *metaritem in currentMetarArray)
These lines are wrong. currentMetarArray is a dictionary, not array, it contains string key & value, so you should access it like in following way-
NSDictionary *jsonDictionary = [NSJSONSerialization JSONObjectWithData:data options:0 error:&error];
NSDictionary *weatherObservation = [jsonDictionary objectForKey:#"weatherObservation"];
then to get nCloud, use like
NSString *nClouds = [weatherObservation objectForKey:#"clouds"];
I go to your URL and get this message {"status":{"message":"the daily limit of 30000 credits for demo has been exceeded. Please use an application specific account. Do not use the demo account for your application.","value":18}}
But you can try my code, it worked for me
NSString *strUrl = #"http://api.geonames.org/weatherIcaoJSON?ICAO=YBBN&username=demo";
NSURL *url = [NSURL URLWithString:strUrl];
NSData *data = [NSData dataWithContentsOfURL:url];
NSError *error;
NSDictionary *json = [NSJSONSerialization JSONObjectWithData:data options:0 error:&error];
NSDictionary *weatherObservation = [json objectForKey:#"status"];
for (id key in weatherObservation) {
id value = [weatherObservation objectForKey:key];
NSLog(#"key = %#, value = %#", key, value);
}
The error thrown is the best clue for how you can fix this.
Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFString objectForKey:]: unrecognized selector sent to instance 0x7f9298554560'
What this means is that you're thinking an object is a dictionary when in reality it isn't.
You can combat this using NSObject methods such as:
[myObject respondsToSelector:(#selector(objectForKey:))]; // will return a boolean value.
to see if the object will respond to the method you hope to send it
or
[myObject isKindOfClass:[NSDictionary class]]; // will return a boolean value.
to determine if the object is a NSDictionary.
What's likely happening, though, is that you have an error in expectation with the Deserialized JSON Data.
Happy bug hunting!
In my iPhone aplication I have a list of custom objects. I need to create a json string from them. How I can implement this with SBJSON or iPhone sdk?
NSArray* eventsForUpload = [app.dataService.coreDataHelper fetchInstancesOf:#"Event" where:#"isForUpload" is:[NSNumber numberWithBool:YES]];
SBJsonWriter *writer = [[SBJsonWriter alloc] init];
NSString *actionLinksStr = [writer stringWithObject:eventsForUpload];
and i get empty result.
This process is really simple now, you don't have to use external libraries,
Do it this way, (iOS 5 & above)
NSArray *myArray;
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:myArray options:NSJSONWritingPrettyPrinted error:&error];
NSString *jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
I love my categories so I do this kind of thing as follows
#implementation NSArray (Extensions)
- (NSString*)json
{
NSString* json = nil;
NSError* error = nil;
NSData *data = [NSJSONSerialization dataWithJSONObject:self options:NSJSONWritingPrettyPrinted error:&error];
json = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
return (error ? nil : json);
}
#end
Although the highest voted answer is valid for an array of dictionaries or other serializable objects, it's not valid for custom objects.
Here is the thing, you'll need to loop through your array and get the dictionary representation of each object and add it to a new array to be serialized.
NSString *offersJSONString = #"";
if(offers)
{
NSMutableArray *offersJSONArray = [NSMutableArray array];
for (Offer *offer in offers)
{
[offersJSONArray addObject:[offer dictionaryRepresentation]];
}
NSData *offersJSONData = [NSJSONSerialization dataWithJSONObject:offersJSONArray options:NSJSONWritingPrettyPrinted error:&error];
offersJSONString = [[NSString alloc] initWithData:offersJSONData encoding:NSUTF8StringEncoding] ;
}
As for the dictionaryRepresentation method in the Offer class:
- (NSDictionary *)dictionaryRepresentation
{
NSMutableDictionary *mutableDict = [NSMutableDictionary dictionary];
[mutableDict setValue:self.title forKey:#"title"];
return [NSDictionary dictionaryWithDictionary:mutableDict];
}
Try like this Swift 2.3
let consArray = [1,2,3,4,5,6]
var jsonString : String = ""
do
{
if let postData : NSData = try NSJSONSerialization.dataWithJSONObject(consArray, options: NSJSONWritingOptions.PrettyPrinted)
{
jsonString = NSString(data: postData, encoding: NSUTF8StringEncoding)! as String
}
}
catch
{
print(error)
}
Try like this,
- (NSString *)JSONRepresentation {
SBJsonWriter *jsonWriter = [SBJsonWriter new];
NSString *json = [jsonWriter stringWithObject:self];
if (!json)
[jsonWriter release];
return json;
}
then call this like,
NSString *jsonString = [array JSONRepresentation];
Hope it will helps you...
I'm a bit late to this party, but you can serialise an array of custom objects by implementing the -proxyForJson method in your custom objects. (Or in a category on your custom objects.)
For an example.
I have an iOS app which connects to a server via OAuth 2.0. I get returned an access token in this form:
{accessToken="521515.ab6dc96.51dca3d53c4236d2d4f4460b151bc58d6ec91e14"}
And I store that in a NSString. The problem I am having is that I ONLY need the part which is in the quotation marks. How can I extract that?
UPDATE
Here us my code:
GTMOAuth2Authentication *auth_instagram;
auth_instagram = [GTMOAuth2ViewControllerTouch authForGoogleFromKeychainForName:#"Instagram" clientID:kMyClientID_instagram clientSecret:kMyClientSecret_instagram];
NSLog(#"%#", auth_instagram);
Printed in the Xcode console is:
GTMOAuth2Authentication 0xb2c0a80: {accessToken="541019.ab6dc96.51dc0d264d2d4f60b151bc8d6ec91e14"}
If I read the class definition at http://code.google.com/p/gtm-oauth2/source/browse/trunk/Source/GTMOAuth2Authentication.h correctly, GTMOAuth2Authentication has a
#property (retain) NSString *accessToken;
so that you can just do
NSString *token = auth_instagram.accessToken;
to get the token as a string.
Remark: Your output
{accessToken="521515.ab6dc96.51dca3d53c4236d2d4f4460b151bc58d6ec91e14"}
is the result of calling the description method of GTMOAuth2Authentication.
This is not JSON. JSON would look like
{ "accessToken" : "521515.ab6dc96.51dca3d53c4236d2d4f4460b151bc58d6ec91e14" }
The right way would be to parse the whole string using the correct format/parser, in this case probably NSJSONSerialization and extract the value from the accessToken element.
NSDictionary *parsedData = [JSONObjectWithData:[string dataUsingEncoding:NSUTF8StringEncoding] options:0 error:NULL];
NSString *value = parsedData[#"accessToken"];
NSArray* components = [accessStr componentsSeparatedByString: "\""];
NSString* requiredStr = [components objectAtIndex: 1];
NSDictionary *dic =[NSJSONSerialization JSONObjectWithData: [YourString dataUsingEncoding:NSUTF8StringEncoding] options: NSJSONReadingMutableContainers error: &e];
//yourstring is the string in which u store and &e is just an NSError u can create urself like NSError *e;
NSString access_Token=[dic objectForKey:#"accessToken"];
What you got there is valid JASON. Try the following:
NSDictionary *loginInfo = [NSJSONSerialization JSONObjectWithData:[#"{accessToken=\"521515.ab6dc96.51dca3d53c4236d2d4f4460b151bc58d6ec91e14\"}" dataUsingEncoding:NSUTF8StringEncoding] options:NSJSONReadingMutableContainers error:nil];
NSString *aToken = [loginInfon objectForKey:#"accessToken"];
I am trying to parse JSON in objective-c but am having trouble. The example in the tutorial I am following only goes to the first level after the parent node. I am trying to get data that is a bit deeper. Any advice on how to do this?
The elements I am trying to get:
Title: data.children[i].data.title
Thumbnail: data.children[i].data.thumbnail
Json: http://www.reddit.com/r/HistoryPorn/.json
NSURL *blogURL = [NSURL URLWithString:#"http://www.reddit.com/r/HistoryPorn/.json"];
NSData *jsonData = [NSData dataWithContentsOfURL:blogURL];
NSError * error = nil;
NSDictionary *dataDictionary = [NSJSONSerialization JSONObjectWithData:jsonData options:0 error:&error];
self.blogPosts = [NSMutableArray array];
NSArray * blogPostsArray = [dataDictionary objectForKey:#"data"];
for (NSDictionary *bpDictionary in blogPostsArray) {
BlogPost * blogPost = [BlogPost blogPostWithTitle:[bpDictionary objectForKey:#"title"]];
blogPost.thumbnail = [bpDictionary objectForKey:#"thumbnail"];
blogPost.url = [NSURL URLWithString:[bpDictionary objectForKey:#"url"]];
[self.blogPosts addObject:blogPost];
}
With the new syntax it should be easier to gets keys in a nested dictionaries. You can know the full keys/indexes path by just drawing a tree, remember that a dictionary starts with braces, and an array starts with brackets. For example let's retrieve the "thumbnail" and "url" value for the first entry in the children array:
NSDictionary *json = [NSJSONSerialization JSONObjectWithData:jsonData options:0 error:&error];
if(!json)
{
// Always handle eventual errors:
NSLog(#"%#",error);
return;
}
NSString* thumbnail= json[#"data"][#"children"][0][#"data"][#"thumbnail"];
NSString* url= json[#"data"][#"children"][0][#"data"][#"url"];
In the method below I'm receiving "EXC_BAD_ACCESS" on the line containing the "urlString" variable. My research suggests that this error occurs when the program sends a message to a variable that has already been released. However since I'm using ARC I'm not manually releasing memory. How can I prevent ARC from releasing this variable too soon?
-(NSMutableArray *)fetchImages:(NSInteger *)count {
//prepare URL request
NSString *urlString = [NSString stringWithFormat:#"http://foo.example.com/image?quantity=%#", count];
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:urlString]];
//Perform request and get JSON as a NSData object
NSData *response = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
//Parse the retrieved JSON to an NSArray
NSError *jsonParsingError = nil;
NSArray *imageFileData = [NSJSONSerialization JSONObjectWithData:response options:0 error:&jsonParsingError];
//Create an Array to store image names
NSMutableArray *imageFileNameArray;
//Iterate through the data
for(int i=0; i<[imageFileData count];i++)
{
[imageFileNameArray addObject:[imageFileData objectAtIndex:i]];
}
return imageFileNameArray;
}
Your problem has nothing to do with ARC. NSInteger isn't a class, so you don't want to be using the %# format. %# is going to send a description method to what the system thinks is an object, but when it turns out not to be one - CRASH. To solve your problem, you have two options:
You might want:
NSString *urlString =
[NSString stringWithFormat:#"http://foo.example.com/image?quantity=%d",
*count];
Make sure the count pointer is valid first!
You might need to change your method signature to be:
-(NSMutableArray *)fetchImages:(NSInteger)count;
and then change the urlString line as follows:
NSString *urlString =
[NSString stringWithFormat:#"http://foo.example.com/image?quantity=%d",
count];
You'll also need to fix all of the callers to match the new signature.
The second option seems more "normal" to me, but without more of your program it's impossible to be more specific.
you also may want to alloc and init the
NSMutableArray *imageFileNameArray;
before adding objects to it, otherwise you'll keep crashing. So you'd have
//Create an Array to store image names
NSMutableArray *imageFileNameArray = [[NSMutableArray alloc] init];