I am trying to parse the multiple bool values. In below code JSONObject is the NSMutableArray.ii is the indexpath. But with the below am getting only one value. This is first time to me handling bool values from json, help me to fetch the bool values inside the answer list array.
BOOL options= [[[jsonObject objectAtIndex:ii] objectForKey:#"Is_Correct"]boolValue] ;
NSLog(#"correct answer %d",options);
NSDictionary* outerArrayElement = jsonObject[1];
NSArray* amswersList = outerArrayElement["AnswersList"];
NSDictionary* innerArrayElement = answersList[0];
NSNumber* is_correctNum = innerArrayElement["Is_Correct"];
BOOL is_correct = [is_correctNum].boolValue;
But one should iterate over the arrays, and also check for nil results in some cases, especially when retrieving the outer array element.
And for testing insert NSLog statements after each step.
Related
Sorry guys, this problem I am running into is pretty trivial. I just can't wrap my head around it so hope someone can help me. Your help is really appreciated. I am getting JSON data through NSURLConnectDelegate with a web API. I get something like this back:
(
{
id = 340
name = Vicent },
{
id = 339
name = Johny },
{
id = 338
name = Eric }
)
and I save it in a NSMutableArray as a global variable. Now, I have a NSSet of "ids". For example:
{
340, 339
}
In the numberOfRowsInSection, I return the set's count. I am trying to load only the ids in the NSSet from the array with the data saved from the webAPI, so I do something like this in cellForRowIndexPath:
for (NSNumber *num in [set allObjects]) {
NSString *newString = [[savedArray objectAtIndex:indexPath.row]
NSString *new = [num stringValue];
if ([new isEqual:newString]) {
}}
How can I just populate the ids I want?
The JSON makes it look like you have an array of dictionaries, which is a reasonable data structure to use as the data source for a table view.
It sounds like you're trying to filter your array to only include the items that are in your set. Is that right?
If so, you could write code that would create a new array containing the subset of your array elements who's ID is also in your set. There are at least a half-dozen ways to do that. One fairly simple approach would be to use the NSArray method indexesOfObjectsPassingTest. You'd pass that method a block of code that would check each array element to see if it's id object was in your set.
That would give you an NSIndexSet with the indexes of the items in your array who's ID are in your set. Then you could use the NSArray method objectsAtIndexes to get an array of only the objects that are also in the set. Something like this (Assuming that your array of dictionaries is called savedArray and your set is called allObjects:
//get the indexes of items in the array savedArray who's id appears in the set allObjects
NSIndexSet *indexes = [savedArray indexesOfObjectsPassingTest:
^(NSDictionary *obj,
NSUInteger idx,
BOOL *stop)
{
return [allObjects member: obj[#"id"]] != nil;
}
];
//Now build an (immutable) array of just the objects who's ID are in the set
NSArray *subArray = [savedArray objectsAtIndexes: indexes];
The array subArray created above is immutable. If you need a mutable array you would need to make a mutable copy, which is a one-line change.
Disclaimer: I still struggle a little with block syntax, so the above might not be exactly correct, but it gives you the general idea.
for (NSDictionary *fbDictionary in self.latestReactionsArray) {
LatestReaction *latestReaction = [[LatestReaction alloc]init];
NSDictionary *subFBDictionary = [fbDictionary objectForKey:#"participant"];
NSString *facebookUserID = [subFBDictionary valueForKey:#"facebook_id"];
NSNumber* reactionIDNum = [fbDictionary valueForKey:#"reaction_id"];
int reactionID = [reactionIDNum intValue];
NSLog(#"what is name%# and %# and %d",facebookUserID, self.latestReactionsArray,reactionID);
}
I want to save all [fbDictionary valueForKey:#"reaction_id"] in an array or dictionary. How do I do this? Thanks.
Try this:
NSArray *reactionIDs = [self.latestReactionsArray valueForKey:#"reaction_id"];
That will give you an array of reaction IDs.
The reflection in Objective C is not powerful enough to get a usable list of properties that you want to map. Instead, you should implement a class method that returns a list of properties you want to map to JSON and use that.
Lastly, a common "Gotcha" is trying to add nil to a dictionary. You'll need to do a conversion from nil to [NSNull null] and back for the conversion to work properly.
I am creating some XML in objective C, I know how to do it however there is the possibility that there could be 800+ values I might be putting into XML, which I am getting from a NSArray of NSDictionaries.
So I was wondering if there is an efficient way of checking for nill or null in a keyvalue that's of type NSString.
Currently this is what my code looks like:
NSMutableArray *xmlItems = [coreDataController readInstallForXML:selectedInstallID];
for (int i = 0; i < [xmlItems count]; i++) {
NSDictionary *currentXMLItem = [xmlItems objectAtIndex:i];
[xmlWriter writeStartElement:#"Items"];
[xmlWriter writeAttribute:#"insID" value:[currentXMLItem valueForKey:#"insID"]];
// there are about another 20 attributes I have to add here.
}
// then write end elemtent etc.
In the code above I have no added any checking but I was hoping someone might have something better for me than adding a bunch of if statements for each attribute.
You can use [NSDictionary allKeysForObject:] to get all keys for the 'nil' values, so you have a list of keys to ignore.
Generating 800 items is not necessarily 'much' or 'slow'. You don't want to do that on the main thread anyway, so just make sure you perform it as a background operation.
use the allKeys method on the NSDictionary to return an NSArray of keys; then iterate through that array and for each key retrieve the value from the dictionary and use one if statement to check the string before writing out the xml element
This question already has answers here:
Appending NSDictionary to other NSDictionary
(3 answers)
Closed 9 years ago.
Im working with flickr and in the sample fetch I get this:
{
"api_key" = {
"_content" = 3c6eeeae4711a5f478d3da796750e06b;
};
format = {
"_content" = json;
};
method = {
"_content" = "flickr.test.echo";
};
nojsoncallback = {
"_content" = 1;
};
stat = ok;
}
This is a dictionary with 5 entries (api_key, format, method, nojsoncallback & stat). The first 4 entires are dictionaries themselves.
First off, there is a 5th element in my original dictionary, which is not a dictionary, it is simply the last entry in the original dictionary (the one stat=ok). Furthermore, I want the _content key in every subentry to appear in my individual cells but I dont want to hardcode any values. Do I HAVE to setup an array?
NSDictionary has a nifty little method called valueForKeyPath. Thats your savior here.
[dict valueForKeyPath:#"api_key._content"]
[dict valueForKeyPath:#"format._content"]
[dict valueForKeyPath:#"method._content"]
[dict valueForKeyPath:#"nojsoncallback._content"]
What it does is traverse the key path and fetch the values of content in each JSON substructure. Otherwise you would have had to written a for-loop and loop through it. Neat huh?
Try this
for (NSString *key in dictionary){
id object = dictionary[key];
if ([object isKindOfClass:[NSDictionary class]]) {
//Now you can work on the dictionary object
}
}
Im getting a response from twitter in the form of a string,
What I need is to send the parts where is a comment to an array,
here an example of the string
[{"geo":null,"coordinates":null,"retweeted":false,...
"text":"#KristinaKlp saluditos y besos d colores!"},{"geo":null,"coordinates...
so what I really need are the posts after "text":" =
#KristinaKlp saluditos y besos d colores!
So, how can I take the string and parse it so I get all the messages in an array hopefully?
Thanks a lot!
I haven't done JSON parsing myself in an iOS App, but you should be able to use a library like the json-framework. This library will allow you to easily parse JSON and generate json from dictionaries / arrays (that's really all JSON is composed of).
SBJson docs:
JSON is mapped to Objective-C types in the following way:
null -> NSNull
string -> NSString
array -> NSMutableArray
object -> NSMutableDictionary
true -> NSNumber's -numberWithBool:YES
false -> NSNumber's -numberWithBool:NO
integer up to 19 digits -> NSNumber's -numberWithLongLong:
all other numbers -> NSDecimalNumber
Since Objective-C doesn't have a dedicated class for boolean values,
these turns into NSNumber instances. However, since these are
initialised with the -initWithBool: method they round-trip back to JSON
properly. In other words, they won't silently suddenly become 0 or 1;
they'll be represented as 'true' and 'false' again.
As an optimisation integers up to 19 digits in length (the max length
for signed long long integers) turn into NSNumber instances, while
complex ones turn into NSDecimalNumber instances. We can thus avoid any
loss of precision as JSON allows ridiculously large numbers.
#page objc2json Objective-C to JSON
Objective-C types are mapped to JSON types in the following way:
NSNull -> null
NSString -> string
NSArray -> array
NSDictionary -> object
NSNumber's -initWithBool:YES -> true
NSNumber's -initWithBool:NO -> false
NSNumber -> number
#note In JSON the keys of an object must be strings. NSDictionary
keys need not be, but attempting to convert an NSDictionary with
non-string keys into JSON will throw an exception.
NSNumber instances created with the -numberWithBool: method are
converted into the JSON boolean "true" and "false" values, and vice
versa. Any other NSNumber instances are converted to a JSON number the
way you would expect.
Tutorials
Are there any tutorials? Yes! These are all tutorials provided by
third-party people:
JSON Framework for iPhone - a Flickr tutorial in three parts by John
Muchow. JSON Over HTTP On The iPhone - by Dan Grigsby. AS3 to Cocoa touch: JSON by Andy Jacobs.
There are other libraries you can check out as well like TouchJSON, JSONKit, Yet Another JSON Library
NSJSONSerialization does the job of converting your JSON data into usable data structures as NSDictionary or NSArray very well. I recommend it, even more because it is part of the Cocoa public interface and it is maintained by Apple.
However, if you want to map the content of your JSON to your Objective-C objects, you will have to map each attribute from the NSDictionary/NSArray to your object property. This might be a bit painful if your objects have many attributes.
In order to automatise the process, I recommend you to use the Motis category (personal project) on NSObject to accomplish it, thus it is very lightweight and flexible. You can read how to use it in this post. But just to show you, you just need to define a dictionary with the mapping of your JSON object attributes to your Objective-C object properties names in your NSObject subclasses:
- (NSDictionary*)mjz_motisMapping
{
return #{#"json_attribute_key_1" : #"class_property_name_1",
#"json_attribute_key_2" : #"class_property_name_2",
...
#"json_attribute_key_N" : #"class_property_name_N",
};
}
and then perform the parsing by doing:
- (void)parseTest
{
NSData *data = jsonData; // <-- YOUR JSON data
// Converting JSON data into NSArray (your data sample is an array)
NSError *error = nil;
NSArray *jsonArray = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:&error];
if (error)
return; // <--- If error abort.
// Iterating over raw objects and creating model instances
NSMutableArray *parsedObjects = [NSMutableArray array];
for (NSDictionary *rawObject in jsonArray)
{
// Creating an instance of your class
MyClass instance = [[MyClass alloc] init];
// Parsing and setting the values of the JSON object
[instance mjz_setValuesForKeysWithDictionary:rawObject];
[parsedObjects addObject:instance];
}
// "parseObjects" is an array with your parsed JSON.
// Do whatever you want with it here.
}
The setting of the properties from the dictionary is done via KeyValueCoding (KVC) and you can validate each attribute before setting it via KVC validation.
I recently had to do this. After looking at the various options out there, I threw JSONKit into my app (I found it on a JSON discussion on StackOverflow). Why?
A) It is VERY VERY simple. I mean, all it has is the basic parsing/emitting functions, what more do you need?
B) It is VERY VERY fast. No overhead - just get the job done.
I should note, I had never done JSON before - only heard of the term and didn't even know how to spell it. I went from nothing, to a working app, in about 1 hour. You just add one class to your app (the .h, .m), instantiate it, and call the parser to a dictionary object. Voila. If it contains an array, you just get the objectForKey, cast it as an NSArray. It's really hard to get simpler than that, and very fast.
For a good comparison of the speed of the different libraries for JSON parsing on iOS, take a look at The Ultimate Showdown.
-(IBAction)btn_parse_webserivce_click:(id)sender
{
// Take Webservice URL in string.
NSString *Webservice_url = self.txt_webservice_url.text;
NSLog(#"URL %#",Webservice_url);
// Create NSURL from string.
NSURL *Final_Url = [NSURL URLWithString:Webservice_url];
// Get NSData from Final_Url
NSData* data = [NSData dataWithContentsOfURL:
Final_Url];
//parse out the json data
NSError* error;
// Use NSJSONSerialization class method. which converts NSData to Foundation object.
NSDictionary* json = [NSJSONSerialization
JSONObjectWithData:data
options:kNilOptions
error:&error];
// Create Array
NSArray* Response_array = [json objectForKey:#"loans"];
NSLog(#"Array: %#", Response_array);
// Set Response_array to textview.
self.txt_webservice_response.text = [NSString stringWithFormat:#"%#"
,Response_array];
}
How about NSJSONSerialization? I've been using it to parse JSON
http://developer.apple.com/library/ios/#documentation/Foundation/Reference/NSJSONSerialization_Class/Reference/Reference.html