I have a JSON string as an NSString object in iOS. I want to parse this and pull out the given parameters in the JSON string. Is there a efficient way to parse this or is the only way to search for substrings etc.?
The way to do it with iOS 5 is to use the NSJSONSerialization class. You will want to first convert your string to an NSData object, and call the class method JSONObjectWithData
NSData *jsonData = [myJsonString dataUsingEncoding:NSUTF8StringEncoding];
NSError *e;
NSDictionary *dict = [NSJSONSerialization JSONObjectWithData:jsonData options:nil error:&e];
Note that JSONObjectWithData will return either an NSDictionary or an NSArray, depending whether your JSON string represents an a dictionary or an array.
A good framework for converting JSON strings to Objective-C objects (NSArray and NSDictionary) is SBJson (Github).
Usage:
NSDictionary *dict = [myJsonString JSONValue];
Related
I am making this app that gets some data from the url (censored). The problem is that I didn't found a solution to get what the PHP script echo.
A normal returned array from that script looks this:
{"user_data": {"id":"78","image":"https://www.i********p.com/uploads/ideas/fun/2017/03/28/78.jpg","idea":"Join Facebook groups related to your passions or hobbies and meet friends.","owner_ID":"1","owner":"Eduard","owner_photo":"https://www.i********p.com/uploads/members/1/1.png","rating":"4","reviews":"1 review","msg":"success"}}
The question is how can I access each value of this array from "user_data" using Objective-c (without a loop)?
The Objective-c code:
- (void)getJSON {
NSError *error;
NSString *url_string = [NSString stringWithFormat: #"https://www.app.i******o.com/getidea.php?topic=%#", ideasTopic];
NSData *data = [NSData dataWithContentsOfURL: [NSURL URLWithString:url_string]];
NSMutableArray *json = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&error];
if (error) {
NSLog(#"Something went wrong: %#", error);
} else {
NSLog(#"json: %#", json);
NSLog(#"IMAGE: %#", [[json getObjectAtIndex:0] getObjectForKey:#"image"]);
}}
Objective-C supports literal version to access dictionary. You can directly access values by using keys.
NSString *imageUrl = json[#"user_data"][#"image"];
Your json is a dictionary of dictionaries. json[#"user_data"] returns a dictionary with keys and values. You can access values for this dictionary through respective keys. json[#"user_data"][#"image"] gives you required value for respective key.
Edit:
You need to change your json variable type to NSDictionary too.
NSDictionary *json = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&error];
The JSON text you provided is deserialized into NSDictionary object (you can check it yourself, by looking up what class a json variable has in your example).
So to get what you want (ex. image), you simply write
json["user_data"]["image"]
Unable to parse json string
I have got the following hard coded json. I tried converting it to dictionary and parse it but Im unable to do so.
NSString *hcResponse = #"{\"status\":1,\"value\":\"Successfully Login\"}";
How to parse such a json into key value pairs?
Finally, I've figured it by myself
//convert the string to nsdata
NSData *jsonData = [hcResponse dataUsingEncoding:NSUTF8StringEncoding];
NSError *error;
//convert the data to json dictionary
NSDictionary *jsonDic = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingAllowFragments error:nil];
my app get data from a php web service and return a NSString
["first name","last name","adress","test#test","000-000-0000","password","code","0"]
How can i get the second element ?
This is a JSON formatted string which you are getting from your web service.
You must be getting bytes from server. Just replace your variable which have bytes stored with my variable "response data".
Code:
NSError* error;
NSArray* myResultArray = [NSJSONSerialization
JSONObjectWithData:responseData options:kNilOptions error:&error];
You will get an array in variable "myResultArray" and you can get all value by index.
Code:
NSString* first name = [myResultArray objectAtIndex:0];
What you have given here is an array and not a string. May be you could provide more details like the exact response and the code that you are trying here.
To Convert a JSON string to NSDictionary all you need to do is:
NSError *jsonError;
NSData *objectData = [jsonString dataUsingEncoding:NSUTF8StringEncoding];
NSDictionary *json = [NSJSONSerialization JSONObjectWithData:objectData
options:nil
error:&jsonError];
And to NSArray :
NSArray *array = [NSJSONSerialization JSONObjectWithData:objectData options:nil error:&jsonError];
NSString *secondElement = array[1];
That web service doesn't return an NSString. It runs data in some format defined by the service, and you convert it to an NSString. Find out what the format actually is, then convert it appropriately, for example using NSJSONSerialization.
The example string your showed here seems wired. This looks more like a array than string. If this is a NSArray then you can do it like this:
NSArray *data = #[#"first name",#"last name", #"adress", #"test#test", #"000-000-0000", #"password", #"code", #"0"];
NSLog (#"Second component = %#", data[1]);
However, if you anticipate this as NSString then this is how you would handle this:
NSString *test = #"[\"first name\",\"last name\",\"adress\",\"test#test\",\"000-000-0000\",\"password\",\"code\",\"0\"]";
NSLog (#"Second component = %#", [test componentsSeparatedByString:#","][1]);
I'm new to JSON and don't understand why this is failing. The JSON is valid according to on-line validation tools, but NSJSONSerilization says this the string is invalid. Why is it invalid?
NSString* JSON = #"{\"Questionnaire\":{\"questionnaireid\":1,\"modifiedDate\":\"2012-12-28 15:27:00\"}}";
if (![NSJSONSerialization isValidJSONObject:JSON]) {
return nil;
}
NSError *jsonParsingError = nil;
NSDictionary* data = [NSJSONSerialization dataWithJSONObject:JSON options:NSJSONReadingMutableContainers error:&jsonParsingError];
why you did serialization when you already created JSON yourself ?
What you should do:
NSData *jsonPayload = [JSON dataUsingEncoding:NSUTF8StringEncoding];
NSDictionary *data = [NSJSONSerialization JSONObjectWithData:jsonPayload
options:kNilOptions error:&error];
Because a JSON Object must be of type NSArray or a NSDictionary while you are passing a NSString.
From the docs:
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.
UPDATE
You probably want to do this:
NSData *jsonData = [JSON dataUsingEncoding:NSUTF8StringEncoding];
NSDictionary *jsonDict = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableContainers error:&err];
quite new to iOS development and objective-c at the same time. I have the following method:
-(NSMutableArray *)fetchDatabaseJSON{
NSURL *url = [NSURL URLWithString:#"http://www.ios.com/ios/responseScript.php"];
NSError *error = nil;
NSURLRequest *request = [NSURLRequest requestWithURL:url];
NSData *data = [NSURLConnection sendSynchronousRequest:request returningResponse:NULL error:&error];
//jsonArray = [NSJSONSerialization JSONObjectWithData:data options:0 error:&error];
//NSLog(#"Array: %#",[jsonArray objectAtIndex:0]);
jsonDictionary = [NSJSONSerialization JSONObjectWithData:data options:0 error:&error];
NSLog(#"Dictionary: %#", jsonDictionary);
return jsonArray;
}
Now the NSLog shows this:
2013-02-03 19:15:37.081 TestConnection[24510:c07] Dictionary: (
Bannana,
Apple,
SomeCheese )
From what I understand that whatever is inside the dictionary doesn't have key-value. How can this be? and how can I fix it? I want to be able to have keys to ease operations on dictionary.
Regards,
JSONObjectWithData may return an NSArray or NSDictionary, depending on the JSON data you give it. If your JSON string is an array, you will have an NSArray. If your JSON data is a dictionary, you will get an NSDictionary.
Convert your JSON data (your data variable) to string and print it out with NSLog. To convert NSData to NSString, use something like:
NSString *myString = [[NSString alloc] initWithData:myData encoding:NSUTF8StringEncoding];
If you print it out and see a JSON array, you simply don't have a dictionary there.. If you can alter the server-code that generates the JSON, you may be able to change that.
One more thing I noticed, you assume that the returning container is mutable. If I'm not mistaken, you need to use an option like NSJSONReadingMutableContainers in the options parameter of JSONObjectWithData to get that.
One last tip, if you want to check in code if you have an NSArray (or NSDictionary), use something like:
if ([obj isKindOfClass:[NSArray class]]) {...}