Update
It appears resultField is the one that has no value. Will look into this, but I'd still appreciate any advice.
Original Post
I've been set the task of coming up with a basic iOS application that simply makes a search request and then displays the results for university work. I tried to use the Google Custom Search engine but could never get it to work on the iPhone so I've had to resort to the depreciated Google Web Search API (The lecturer is okay with this).
Now, I'm able to make the request, and it returns the JSON data as intended, which I now must parse, I think. Sadly I only have a week to do this, which is crazy as I've never worked with JSON before.
What I'd like is if someone could help me get off the ground with a pointer or two in how to get even just a basic parsing of the JSON data.
I've looked around on Stackoverflow and saw some things that might be helpful like the breakdown structure in the selected answer here.
The person put this together, which when shown in the code makes some sense to me:
A great structure explanation
dictionary (top-level)
sethostname (array of dictionaries)
dictionary (array element)
msgs (string)
status (number)
statusmsg (string)
warns (array)
??? (array element)
Sadly I can't even begin to do the same with the code generated in my app. It takes the form similar to this example code, courtesy of google - I'm no Paris Hilton fan!
Example code from Google.
{"responseData": {
"results": [
{
"GsearchResultClass": "GwebSearch",
"unescapedUrl": "http://en.wikipedia.org/wiki/Paris_Hilton",
"url": "http://en.wikipedia.org/wiki/Paris_Hilton",
"visibleUrl": "en.wikipedia.org",
"cacheUrl": "http://www.google.com/search?q\u003dcache:TwrPfhd22hYJ:en.wikipedia.org",
"title": "\u003cb\u003eParis Hilton\u003c/b\u003e - Wikipedia, the free encyclopedia",
"titleNoFormatting": "Paris Hilton - Wikipedia, the free encyclopedia",
"content": "\[1\] In 2006, she released her debut album..."
},
{
"GsearchResultClass": "GwebSearch",
"unescapedUrl": "http://www.imdb.com/name/nm0385296/",
"url": "http://www.imdb.com/name/nm0385296/",
"visibleUrl": "www.imdb.com",
"cacheUrl": "http://www.google.com/search?q\u003dcache:1i34KkqnsooJ:www.imdb.com",
"title": "\u003cb\u003eParis Hilton\u003c/b\u003e",
"titleNoFormatting": "Paris Hilton",
"content": "Self: Zoolander. Socialite \u003cb\u003eParis Hilton\u003c/b\u003e..."
},
...
],
"cursor": {
"pages": [
{ "start": "0", "label": 1 },
{ "start": "4", "label": 2 },
{ "start": "8", "label": 3 },
{ "start": "12","label": 4 }
],
"estimatedResultCount": "59600000",
"currentPageIndex": 0,
"moreResultsUrl": "http://www.google.com/search?oe\u003dutf8\u0026ie\u003dutf8..."
}
}
, "responseDetails": null, "responseStatus": 200}
This is the code so far, which as you'll learn quickly does not really do much else than return code similar to the code above.
**My code.**
// query holds the search term
query = [query stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
//append theQuery with search URL
NSString *tempString = [NSString stringWithFormat:#"%#/%#", #"https://ajax.googleapis.com/ajax/services/search/web?v=1.0&q=", theQuery];
//Create NSURL out of tempString
NSURL *url = [NSURL URLWithString:tempString];
// Create a request object using the URL.
NSURLRequest *request = [NSURLRequest requestWithURL:url];
// Prepare for the response back from the server
NSHTTPURLResponse *response = nil;
NSError *error = nil;
NSData *responseData = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
NSDictionary *dictionary = [NSJSONSerialization JSONObjectWithData:responseData options:NSJSONWritingPrettyPrinted error:&error];
NSDictionary* resultField = [NSDictionary dictionaryWithDictionary:[dictionary objectForKey:#"results"]];
// Send a synchronous request to the server (i.e. sit and wait for the response)
// Check if an error occurred
if (error != nil) {
NSLog(#"%#", [error localizedDescription]);
// Do something to handle/advise user.
}
// Convert the response data to a string.
NSString *responseString = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];
NSArray *results = [dictionary objectForKey:#"results"];
//set label's text value to responseString's value.
endLabel.text = responseString;
Now the main issue I've encountered is that the results array is null all the time. I could really do with a point in the right direction here. Thank you.
It looks like you're having trouble traversing the data structure parsed out of the JSON.
NSDictionary *dictionary = [NSJSONSerialization JSONObjectWithData:responseData options:NSJSONWritingPrettyPrinted error:&error];
Assuming the data you passed in is good, this dictionary contains the top-level structure. It has three keys responseData, responseDetails, and responseStatus. (You could see this by NSLogging the dictionary.)
You're then querying that dictionary for the key results. It doesn't exist, so your resultField variable is set to nil. The dictionary's value for the key responseData is another dictionary which does contain a key results -- you need that middle step.
Also, the value for the results key in that second dictionary is an array (of more dictionaries), not a dictionary itself.
There is no need to create a new dictionary each time. For easier reading I'd recommend something like:
[[dictionary objectForKey:#"responseData"] objectForKey:#"results"]
There you have the array of results. You can then add
[ [dictionary objec...] objectAtIndex:0]
Related
So I was working on a project that required me to work with some JSON, I was running into a few issues regarding the best way of representing things. First of, this is how the JSON looks:
"phoneList": [
{
"phoneReason": "End of Contract",
"phoneType": [
{
"id": 5,
"phoneType": "Android Smartphone"
}
]
}
]
I want to know the most appropriate way of representing this.
For example, I do know that that my phoneReason will just be a simple NSString while my phoneType is actually a NSArray. However,I wasn't sure how to represent a)the id, I know this is an integer, but should this be an NSInteger or an NSNumber and b)could someone point me in the direction of some sample code where I can understand how to model a dictionary object containing an integer and a string and also where I can understand how to model an array of dictionaries.
My other question is also similar in that say I'm actually posting something, how do I model this, specifically say for like dictionary type (JSON Curly Brace)objects that contain a number/integer and a string.
For example, this is the JSON I'm trying to model and then do something like this:
"phoneReason": "Upgrade",
"phoneInfo": {
"id": "2"
},
//And then I want to pass ID
-(void) createOurRequest:(NSNumber *)id {
NSDictionary *myDictionary = #{
#"phoneReason" : [NSString stringWithFormat:#"%i", s elf.dat.reason],
//How do I then represent the phoneInfo element exactly?
};
Sorry, for the clumsy question, would really appreciate any guidance on modeling JSON in iOS or just generally.
I'm assuming you're asking questions a) and b), and also how to model a JSON.
a) The unfortunate thing with Obj-C is that all collection elements have to be objects. Integers are value types, so they will need to be converted to NSNumbers to work. However, if you're parsing a JSON string, the builtin JSON parser does it for you. I'll describe it below.
b) The model is based on the JSON. You describe the object collection and the parser will determine the model for you. In your example, you would have a NSDictionary<NSString *: NSArray<NSDictionary<NSString *: id>*>*>. The innermost element has value of id because you can either have an NSString ("End of Contract") or an NSArray ("phoneType": [ { "id": 5, "phoneType": "Android Smartphone" } ])
Of course, the model is defined by your JSON, so if you run it through a parser, you get a structured object. You can access each element based on your model (object[#"phoneList"][#"phoneReason"]).
The class method to use is:
+ (id)JSONObjectWithData:(NSData *)data
options:(NSJSONReadingOptions)opt
error:(NSError **)error
Where you pass it a NSData representation of your string, options (or 0), and a NSError pointer (error*). You get back a parsed JSON with the proper structure you defined.
NSDictionary *parsedJSONObject = [NSJSONSerialization JSONObjectWithData:jsonData options:0 error:NULL
I have no options to use and I know there will be no error, so I pass nothing for those parameters. The resulting object will be in whatever structure your JSON is.
Using the objects and the json layout you provided in your first example, this is how I would go about creating the dictionaries and arrays to get the json in the format you specified. Hopefully this helps make it a little clearer for you.
// example constructor method
-(void) jsonStringWithPhoneReason:(NSString*)reason phoneId:(NSInteger)phoneId phoneType:(NSString*)phoneType
{
// create device detail dictionary
NSDictionary *deviceOneDetail = #{
#"id" : #(phoneId), // <- set phone id as NSNumber
#"phoneType" : phoneType // <- set your string phone type
};
// create device dictionary
NSDictionary *deviceOne = #{
#"phoneReason" : reason, // <- set your phone reason string
#"phoneType" : #[deviceOneDetail] // <- set your phone type dictionary within an array
};
// create phone list dictionary with any device dictionaries you want to add
NSDictionary *phoneListDict = #{
#"phoneList" : #[
deviceOne, // <- add your device to the phone list array of dictionaries
// deviceTwo...
]
};
NSString *jsonString = [self convertToJsonString:phoneListDict]; // <- convert the dictionary into a json string and use however you wish
// your json string should now look like this assuming you pass 'End of Contract', 5 & 'Android Smartphone' as arguments to this method
// {"phoneList":[{"phoneReason":"End of Contract","phoneType":[{"id":5,"phoneType":"Android Smartphone"}]}]}
}
-(NSString*) convertToJsonString:(NSDictionary*)dictionary
{
NSError *error;
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:dictionary
options:0 // Pass 0 if you don't care about the readability of the generated string
error:&error];
if (error)
{
NSString *errorDesc = [NSString stringWithFormat:#"Error creating json data from dictionary: %#", error.localizedDescription];
NSLog(#"ERROR: %#", errorDesc);
jsonData = nil;
return nil;
}
NSString *returnString = nil;
if(jsonData != nil)
{
returnString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
}
return returnString;
}
So the last two days I have been struggling to get data from and to a JSON file, this is because it has multiple levels and the same names. I did not set up this file and can't change the structure so I have to get it working in the way it is. To Pharse JSON form a single level is no problem and it works fine, what I need is to get separate data block from "GOV" and "PRIV" then I need a data block "GENERAL" and "LOCAL" and within those I need to be able to get the "Hospital information as a block but also the separate values. Now I have been trying to get this done for two days and I know im doing something wrong but cant figure it out. I do get data back for example the "GOV" block but then in the output window it is showing a array with access data (<__NSCFArray 0x7fe711f58800>) and the output... I cant break up this output and that is what I need because every value needs to be in a text file in a tableview cell. I know { } denotes NSDictionary [ ] denotes NSArray and I have been reading a lot about JSON and I get the concept but There is little to non for me understandable info when it comes to multi level JSON and equal names (hospital) in this case. I have tried all the available option I could find here on StackOverflow but no succes. So if somebody can push me in the right way I will be gratefull.. part of the code:
NSURL *url = [NSURL URLWithString:getDataURL];
NSData * data = [NSData dataWithContentsOfURL:url];
_jsonArray = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:nil];
_AppListArray = [[NSMutableArray alloc] init];
NSArray *wrapper= [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
NSDictionary *avatars = [wrapper objectAtIndex:0];
for(NSDictionary *apps in _jsonArray) {
if([[apps objectForKey:#"title"] isEqualToString:#"GOV"]){
NSDictionary*tmp = [apps objectForKey:#"hospital"];
_AppListArray = [tmp objectForKey:#"area"];
}
}
//returns error because _ApplistArray is an array and it can't read the data from the objectkey
for (int i = 0; i < _jsonArray.count; i++)
{
NSString *appName = [[_AppListArray objectAtIndex:i] objectForKey:#"hospitalname"];
NSString *appCondition = [[_AppListArray objectAtIndex:i] objectForKey:#"condition"];
NSString *app avgrating = [[_AppListArray objectAtIndex:i] objectForKey:#"avgrating"];
[_AppListArray addObject:[[Applist alloc]initWithAppName:appName andAppCondition:appCondition andAppURL:appURL]];
}
The _ApplistArray does return the 1ste Hospital data block but as an array and this is were I get stuck.. I need to get another level deeper.....Again the solution probably is easy but JSON is something I never worked with this is my first go. The JSON where I need to get the data from:
[
-{
-hospital: {
-area: [
-{
-hospital: [
-{
hospitalname: "ABC",
avgrating: "2,6",
condition: "UPDATE NEEDED",
},
-{
hospitalname: "DEF",
avgrating: "4,2",
condition: "FINE",
},
],
name: "GENERAL"
}
]
},
title: "GOV"
},
-{
-hospital: {
-area: [
-{
-hospital: [
-{
hospitalname: "GHI",
avgrating: "3",
condition: "INSTALL NEW",
},
-{
hospitalname: "JKL",
avgrating: "0",
condition: "NEW",
},
],
name: "LOCAL"
}
]
},
title: "PRIV"
}
]
Here you go.
NSArray *hospitals = [jsonArray objectForKey:#"mainKey"];// I assumed you getting with some key but change based on your requirement
for (NSDictionary *mainData in hospitals){ // Start of Main Hospital
NSDictionary *hospital = [mainData objectForKey:#"hospital"];
NSArray *areas = [hospital objectForKey:#"area"];
for(NSDictionary *area in areas){// Start of Area
NSArray *innerHospitals = [area objectForKey:#"hospital"];
for(NSDictionary *innerHospital in innerHospitals){
NSString *hospitalName = [innerHospital objectForKey:#"hospitalname"];
NSString *avgrating =[innerHospital objectForKey:#"avgrating"];
NSString *condition =[innerHospital objectForKey:#"condition"];
// Do What Ever you want here
}
NSString *name =[area objectForKey:#"name"];
}// End Of Area
NSString *title =[mainData objectForKey:#"title"];
} // End of Main Hospital
I haven't tested it. But i assume this will work. Have a try and let me know what happens.
The problem is that you need 2 for loops for each "Area".
Area is an Array (1st loop) and each hospital is another Array (2nd loop).
And inside each hospital element is the dictionary with the values you need.
ignoring loops this is how you get the first hospitalname(ABC) assuming _AppListArray has the contents of Area
NSString *appName = _AppListArray[0][#"hospital"][0][#"hospitalname"];
For each 0 you will replace it with the counters for the for loops.
I'll keep this brief. I'm using this code to parse JSON from a local file into an array of objects:
-(void)populateData
{
NSString* sourcePath = [[NSBundle mainBundle]pathForResource:#"ships" ofType:#"json"];
//get json string
NSString* JSONData = [[NSString alloc] initWithContentsOfFile:sourcePath encoding:NSUTF8StringEncoding error:nil];
NSData* data = [JSONData dataUsingEncoding:NSUTF8StringEncoding];
//put json in array
ships = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:nil];
NSLog(#"%#", ships);
}
(Note: only showed one for the sake of brevity, there's ~20 entries in each one)
This method works for JSON formatted like this:
[
{
"name": "Santa Maria",
"operator": "Kingdom of Spain",
"flag": "flag_spain"
}
]
It returns null for JSON formatted like this:
[
{
"name": "Santa Maria",
"operator": "Kingdom of Spain",
"flag": "flag_spain",
"launched": "November 19, 1890",
"fate": "Destroyed in Havana, Cuba in Feburary 1898."
"cost":"$4,677,788.75",
"image": "maine_img",
"image_attribution": "Image is in the public domain."
}]
I haven't the faintest idea of why the smaller one works while the larger one doesn't. Any help would be appreciated.
There is a comma missing after:
"fate": "Destroyed in Havana, Cuba in Feburary 1898."
It's due to a syntax error on this line:
"fate": "Destroyed in Havana, Cuba in Feburary 1898."
(missing comma at the end)
There are tools to spot this kind of errors. For instance, http://jsonlint.com. This one seems to have better error messages http://jsonformatter.curiousconcept.com/.
And excuse me, but converting from NSData to NSString and then back to NSData is just pointless. Just call dataWithContensOfFile: and be done with it.
I'm working with data from a Foursquare API.
I want to get a list of coffee shops, and am getting that back correctly (I'm using RestKit)... but once I get that list, on my end I need to filter out any coffee shop that is a "Starbucks".
So right now I only know how to pull in all coffee shops, but I don't know how to parse that data once I have it before I serve it into the app table view so that there will be no Starbucks coffee shops listed.
Any ideas how I could do that? Let me know if you need any of my code snippets posted that might help. Thanks!
EDIT
Normal response type from the API would be:
"venue": [{
"name": "ABC Coffee Shop", {
So I would need to take "name" and filter out any name that was "Starbucks".
If FourSquare doesn't let you apply a filter to the request, to filter on the name "Starbucks" then what I would do with this is the following.
I would start by deserializing the response into a JSON Object, which in this case will be a dictionary.
NSError *error = nil;
NSDictionary *responseDict = [[NSJSONSerialization JSONObjectWithData:foursquareResponse options:0 error: &error];
NSArray *starbucks = nil;
if (!error) {
NSArray *coffeeShops = responseDict[#"venue"];
starbucks = [coffeeShops filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:#"name = 'Starbucks'"]];
} else {
// handle the error
}
NSLog(#"Starbucks: %#", starbucks");
I didn't test this code but I think it should get you on your way.
Looks like JSON to me, you could just use the built in JSON parser, the NSJSONSerialization class. Here is a method I built that takes an NSData JSON parameter, deserializes it and returns a dictionary.
- (NSMutableDictionary *)deserialize: (NSData *)data {
return [[NSJSONSerialization JSONObjectWithData:data options:kNilOptions error: nil] mutableCopy];
}
I don't know the structure of Foursquare's response inside out, so you might want to NSLog() the returned dictionary to see how you can now reference to it.
I've got a question regarding parsing a JSON response within iOS5.
Currently, I'm following this guide here to help me parse the JSON response returned from a third-party mapping service.
Everything works, except that the JSON response returned by the third-party server is somewhat different from the one shown in the guide itself.
In a nutshell, the overall structure of the entire JSON response looks something like this:
{
"directions": [....],
"messages": [....],
"routes":
{
"features": [
{
"attributes": {....},
"geometry":
{
"paths": [....]
}
}
]
}
}
This is the actual JSON query URL.
By using this line of code,
NSDictionary * jsonResponse = [NSJSONSerialization JSONObjectWithData:responseData options:kNilOptions error:&error];
I am able to sucessfully get the jsonResponse dictionary to report that it has 3 key/value pairs, but my ultimate goal is to retrieve the array stored in 'routes.features.geometry.paths'.
This is my current code block that gets the final set of array values:
NSDictionary * jsonResponse = [NSJSONSerialization JSONObjectWithData:responseData options:kNilOptions error:&error];
NSArray * jsonArray = [jsonResponse valueForKeyPath:#"routes.features.geometry.paths"];
jsonArray = [jsonArray objectAtIndex:0];
jsonArray = [jsonArray objectAtIndex:0];
I was wondering if anyone might have a better idea of how I should go about doing this in a more elegant fashion?
Thanks a lot in advance!
You can't just use it as JSON object because it will be working as JSON (Plain String) and you need to parse it so for your problem you can do like this to directly go to paths
NSArray *arr = [[[[jsonResponse objectForKey:#"routes"] objectForKey:#"features"] objectForKey:#"geometry"] objectForKey:#"paths"];
Now you can access your paths data from "arr" array
UPDATE:
NSArray *arr = [[[[[jsonResponse objectForKey:#"routes"] objectForKey:#"features"] objectAtIndex:0] objectForKey:#"geometry"] objectForKey:#"paths"];
as features element is an Array so traverse array first then goto its elements