I have a json file that looks like this:
{
"data":
{
"level": [
{
//bunch of stuff
}
]
}
}
Now I want to convert that into a array of levels that I can access. If I take away the {"data: part, then I can use this:
NSData *allLevelsData = [[NSData alloc] initWithContentsOfFile:fileLoc];
NSError *error = nil;
NSMutableDictionary *allLevels = [NSJSONSerialization JSONObjectWithData:allLevelsData options:kNilOptions error:&error];
if(!error){
NSMutableArray *level = allLevels[#"level"];
for (NSMutableDictionary *aLevel in level){
//do stuff with the level...
But I have to have the {"data: as part of the file, and I can't figure out how to get a NSData object out of the existing NSData object. Any ideas?
Don't you need to pull the level NSArray out of the data NSDictionary first?
NSData *allLevelsData = [[NSData alloc] initWithContentsOfFile:fileLoc];
NSError *error = nil;
NSDictionary *dataDictionary = [NSJSONSerialization JSONObjectWithData:allLevelsData options:kNilOptions error:&error];
if(!error){
NSArray *levels = dataDictionary[#"data"][#"level"];
for (NSDictionary *aLevel in levels){
//do stuff with the level...
You won't get mutable objects back by default and declaring the variables as mutable doesn't make them so. Take a mutableCopy of the result instead (assuming you really do need mutability).
Why are you trying to prune ahead of time? If you decode the original JSON, you'll be able to extract the level array from the data dict in the decoded dict.
It's not clear what else you're trying to accomplish or why you are going the path you ask about. Note, this doesn't necessarily mean your path is wrong, just that without a clearer indication of what goal you're really trying to accomplish or what you've actually tried (and errored/failed, along with how it failed), you're likely only to get vague/general answers like this.
Related
I'm trying to take out the "lasttradeprice" in https://www.allcrypt.com/api.php?method=singlemarketdata&marketid=672 but I can't seem to figure out how to grab the "lasttradeprice" piece.
How would I 'filter' the "price" out? None of the other information is relevant.
Current Code:
NSURL * url=[NSURL URLWithString:#"https://www.allcrypt.com/api.php?method=singlemarketdata&marketid=672"]; // pass your URL Here.
NSData * data=[NSData dataWithContentsOfURL:url];
NSError * error;
NSMutableDictionary * json = [NSJSONSerialization JSONObjectWithData:data options: NSJSONReadingMutableContainers error: &error];
NSLog(#"%#",json);
NSMutableArray * referanceArray=[[NSMutableArray alloc]init];
NSMutableArray * periodArray=[[NSMutableArray alloc]init];
NSArray * responseArr = json[#"lasttradeprice"];
for(NSDictionary * dict in responseArr)
{
[referanceArray addObject:[dict valueForKey:#"lasttradeprice"]];
[periodArray addObject:[dict valueForKey:#"lasttradeprice"]];
}
NSLog(#"%#",referanceArray);
NSLog(#"%#",periodArray);
NOTE: Keep in mind I've never worked with JSON before so please keep your answers dumbed down a tad.
Key value coding provides an easy way to dig through that data. Use the key path for the values you want. For example, it looks like you could get the array of recent trades using the path "return.markets.OMC.recenttrades" like this (assuming your code to get the json dictionary):
NSArray *trades = [json valueForKeyPath:#"return.markets.OMC.recenttrades"];
That's a lot more concise than having to dig down one level at a time.
The value returned for a given key by an array is the array of values returned by the array's members for that key. In other words, you can do this:
NSArray *recentprices = [trades valueForKey:#"price"];
And since that's just the next step in the key path, you can combine the two operations above into one:
NSArray *recentprices = [json valueforKeyPath:#"return.markets.OMC.recenttrades.price"];
The only down side here is that there's no real error checking -- either the data matches your expectations and you get back your array of prices, or it doesn't match at some level and you get nil. That's fine in some cases, not so much in others.
Putting that together with the relevant part of your code, we get:
NSURL *url = [NSURL URLWithString:#"https://www.allcrypt.com/api.php?method=singlemarketdata&marketid=672"];
NSData *data = [NSData dataWithContentsOfURL:url];
NSError *error = nil;
NSMutableDictionary *json = [NSJSONSerialization JSONObjectWithData:data options: NSJSONReadingMutableContainers error:&error];
NSArray *recentprices = [json valueforKeyPath:#"return.markets.OMC.recenttrades.price"];
Update: I just noticed that you want the "lasttradeprice", not the array of prices. Given that, the key path to use is simply #"return.markets.OMC.lasttradeprice", and the value you'll get back will be a string. So replace the last line above with:
NSString *lastTradePrice = [json valueforKeyPath:#"return.markets.OMC.lasttradeprice"];
The value you want is buried a few dictionaries deep. One general idea might be to dig recursively, something like this:
- (BOOL)isCollection:(id)object {
return [object isKindOfClass:[NSArray self]] || [object isKindOfClass:[NSDictionary self]];
}
- (void)valuesForDeepKey:(id)key in:(id)collection results:(NSMutableArray *)results {
if ([collection isKindOfClass:[NSDictionary self]]) {
NSDictionary *dictionary = (NSDictionary *)collection;
if (dictionary[key]) [results addObject:dictionary[key]];
for (id deeperKey in [dictionary allKeys]) {
if ([self isCollection:dictionary[deeperKey]]) {
[self valuesForDeepKey:key in:dictionary[deeperKey] results:results];
}
}
} else if ([collection isKindOfClass:[NSArray self]]) {
NSArray *array = (NSArray *)collection;
for (id object in array) {
if ([self isCollection:object]) {
[self valuesForDeepKey:key in:object results:results];
}
}
}
}
Then call it like this:
NSMutableArray *a = [NSMutableArray array];
[self valuesForDeepKey:#"lasttradeprice" in:json results:a];
NSLog(#"%#", a);
I'm evaluating RestKit to use in my project. I've created a simple app that loads some JSON and maps it into Objective-C objects. I'm having a problem correctly mapping a JSON object that has numeric and logical fields. E.g.
{
"integerValue":"5",
"booleanValue":"YES",
}
I want these to map to the following properties in my data object:
#property int integerValue;
#property BOOL booleanValue;
It didn't work out of the box, so I've created a value transformer for that:
[_activityMapping setValueTransformer:[RKBlockValueTransformer valueTransformerWithValidationBlock:^BOOL(__unsafe_unretained Class inputValueClass, __unsafe_unretained Class outputValueClass) {
if([inputValueClass isSubclassOfClass:[NSString class]] && [outputValueClass isSubclassOfClass:[NSNumber class]]) {
return YES;
}
else {
return NO;
}
} transformationBlock:^BOOL(id inputValue, __autoreleasing id *outputValue, __unsafe_unretained Class outputClass, NSError *__autoreleasing *error) {
if([[inputValue class] isSubclassOfClass:[NSString class]] && [outputClass isSubclassOfClass:[NSNumber class]]) {
NSString *inputString = (NSString *)inputValue;
if([inputString isEqualToString:#"YES"] || [inputString isEqualToString:#"NO"]) {
*outputValue = [NSNumber numberWithBool:[inputString boolValue]];
}
else {
*outputValue = [NSNumber numberWithInt:[inputString intValue]];
}
}
else {
*outputValue = [inputValue copy];
}
return YES;
}]];
This code works, but looks ugly. Note how I have to check the input value to see if it's a boolean or an integer. Any suggestions on an elegant solution to this problem?
Please note that I'm using RestKit. I do know about NSJSONSerialization and know how to parse JSON in code. If you suggest a non-RestKit solution, please explain why do you not recommend using RestKit.
The issue is not occurring at the RestKit level but at the JSON level itself.
According to the JSON spec Boolean values should be represented with true/false not YES/NO. If you update your JSON to be semantically correct then RestKit should do the right thing.
Ok. So according to my understanding of your answer, your main problem lies in mapping the data in the JSON object to their very own designated variables.
So, I'd recommend using the conventional NSJSONSerialization approach.
So, first up. You need to store your JSON object in an NSData object. Now, you're most likely downloading the data from a simple URL. So, this is what you'd do :
//This part is just to download the data. If you're using another method - that's fine. Just make sure that the download is in NSData format
NSURL *url = [[NSURL alloc] initWithString : #"YOUR_URL_HERE"];
NSURLRequest *request = [[NSURLRequest alloc] initWithURL : url];
NSData *jsonData = [NSURLConnection sendSynchronousRequest:request
returningResponse:nil
error:nil];
Now, you need to map those to the NSDictionary... Here's how :
//This is the actual NSJSONSerialization part.
NSDictionary *jsonDict = [NSJSONSerialization JSONObjectWithData:jsonData
options:NSJSONReadingMutableLeaves
error:nil];
Now, just map the values to your designated properties.
_integerValue = (int)[jsonDict objectForKey:#"integerValue"];
_booleanValue = (BOOL)[jsonDict objectForKey:#"booleanValue"];
This is my first native iOS app, so please bear with..
How would I construct this json data in a NSDictionary (I would guess thats how I would do it) so I cand make it part of my request body.
{
"Properties":{
"Description":"String content",
"Domain":"String content",
"GroupID":"String content",
...
},
"Foo":{....},
}
Yes, use a dictionary, created using literals or code.
NSDictionary* jsonDict = #{#"Properties":#{#"Description":#"String content",#"Domain":#"String content",#"GroupID":#"String content",},#"Foo":{....},}
Convert the dictionary into JSON data ready for posting.
NSError *error = nil;
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:jsonDict options:0 error:&error];
I am trying to convert raw json string to NSDictionary. but on NSDictionary i got different order of objects as on json string but i need exactly same order in NSDictionary as on json string. following is code i have used to convert json string
SBJSON *objJson = [[SBJSON alloc] init];
NSError *error = nil;
NSDictionary *dictResults = [objJson objectWithString:jsonString error:&error];
From NSDictionary's class reference:
The order of the keys is not defined.
So, basically you can't do this when using a standard NSDictionary.
However, this may be a good reason for subclassing NSDictionary itself. See this question about the details.
NSDictionary is an associative array and does not preserve order of it's elements. If you know all your keys, then you can create some array, that holds all keys in correct order (you can also pass it with your JSON as an additional parameter). Example:
NSArray* ordered_keys = [NSArray arrayWithObjects: #"key1", #"key2", #"key3", .., nil];
for(NSString* key is ordered_keys) {
NSLog(#"%#", [json_dict valueForKey: key]);
}
//parse out the json data
NSError* error;
NSDictionary* json = [NSJSONSerialization
JSONObjectWithData:responseData //1
options:kNilOptions
error:&error];
NSArray* latestLoans = [json objectForKey:#"loans"]; //2
NSLog(#"loans: %#", latestLoans); //3
Source: Follow this link http://www.raywenderlich.com/5492/working-with-json-in-ios-5
Good tutorial but works only on iOS5
I use the following code to create a JSON file.
// Some data in keys and vals.
NSDictionary* dictionary = [NSDictionary dictionaryWithObjects:vals forKeys:keys];
NSError* writeError = nil;
NSData* jsonData = [NSJSONSerialization dataWithJSONObject:dictionary
options:NSJSONWritingPrettyPrinted error:&writeError];
NSString* path = #"json.txt";
[jsonData writeToFile:path atomically:YES];
How can I output a JSONP file? Is there a Cocoa framework I can use?
Update: In the meantime, I used a quick-and-dirty solution: I read in the JSON file just written before to the disc and add the missing JSONP-function to the string. Then, I write the file a second time. I think that's not worth being the answer to my question. So I will leave this question open to a smarter solution.
You could convert the JSON data to a string, wrap it in your function call and then write it to a file. Example:
NSData* jsonData = [NSJSONSerialization dataWithJSONObject:dictionary
options:NSJSONWritingPrettyPrinted
error:NULL];
NSMutableString *jsonString = [[[NSMutableString alloc] initWithData:jsonData
encoding:NSUTF8StringEncoding] autorelease];
[jsonString insertString:#"functionCall(" atIndex:0];
[jsonString appendString:#");"];
[jsonString writeToFile:path atomically:YES encoding:NSUTF8StringEncoding error:NULL];
(I'm using a mutable string here for better memory efficiency.)
I don't know objective-c or Cocoa. (I use python on MacOS to create JSNOP responses), but it's a simple thing to do.
The basic idea is to wrap the JSON data in a javascript function call:
functionCall({"Name": "Foo", "Id" : 1234, "Rank": 7});
The tricky part is that the function name, "functionCall", is set by the browser and AFAIK the name of that query parameter is not standardized. jQuery uses jsonCallback. Other's use json or callback. So the request url must be checked for that callback name and that function name must be used to wrap the json data.