Using Restkit in my iOS project and the api is getting back a generic array of strings. How do I get access to those array of strings?
This is what is returned by the api.
{
"servers": ["http://myserver.com", "http://myotherserver.com"]
}
Assuming the response is an NSDictionary:
strings = [{response_object} objectForKey: #"servers"]
Will return an NSArray of the strings held in the servers key.
Replace {response_object} with whatever your response is. I may not be understanding your question though, it's quite vague.
Related
I am using one web service in my app. Unfortunately I am not expecting the
response to be auto sorted based on the keys. I need the original response as
it is in web. Can anyone let me know how to do this in iOS app.I am using the
following code to show the response.
NSDictionary *response = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
JSON objects have unordered keys. iOS is not sorting the keys in the data structure. It's just sorting them when you print out the result (for convenience). Internal to the data structure, there is no guaranteed order. It depends on how things hash.
There is no way to use NSJSONSerialization to create an "ordered dictionary" since ordered dictionaries don't exist in JSON. The way you fix this is to use a list of dictionaries, such as:
[ { "First": "A" }, { "Second", "B" } ]
This is promised to stay in order because it's a list.
If you can't change the format, and the format relies on order, then it's not proper JSON and you'll have to parse it some other way. Typically I try to do simple string parsing (splitting on newlines for instance) to find large valid JSON "chunks" that can be handed to the parser.
I know how to parse json object from NSString using NSData and NSDictionary, but I didn't find how to parse multiple json object if I get message like this:
{
"msg_type" : "fist_json",
"field" : "param"
}
{ "second_json_field": [
{
"name_picture": "0.png",
"data_picture":"something"
},
{
"data_values": "something"
} ]
}
{
"third_msg" : "hello"
}
It's not valid JSON, so you can't parse it. A JSON document is either a single array, or a single object (dictionary). Three objects are not valid JSON. You could put square brackets around everything, put commas in the right places, and parse it, getting an array back. Finding the places for the commas without writing a full-blown JSON parser is tricky.
If this is what the server gave you, ask the server people to fix their broken server. If your code for some reason combined three JSON messages into one, then don't do that.
I'm guessing this is not possible in one go. Your provided example text might look like JSON, but it isn't (valid).
I think the service that serves you this response should be 'fixed'.
I am using AFNetworking to retrieve JSON data from a web service. Part of the response string I get is:
{"DATA":{"LEASE TYPE":"3 Yrs + 0 renew of 0 Yrs","LANDLORD":"","TENANT":"test comp"...
and so on. The order of the key values in the "DATA" dictionary ("LEASE TYPE","LANDLORD","TENANT"...) is important for presentation purposes. However, when AFNetworking calls NSJSONSerialization's:
+ (id)JSONObjectWithData:(NSData *)data options:(NSJSONReadingOptions)opt error:(NSError **)error;
method, the returned dictionary has the keys in a different order.
I notice that the AFJSONRequestOperation object has the server's response stored as an NSString, with everything in the correct order. However I'm not keen on parsing the JSON by hand if I can avoid it.
Can anyone suggest a way that will let me get at / keep the keys in their original order?
Thanks.
If the order is important use an array not a dictionary, dictionaries are be by their nature unordered. Or add an array of dictionary keys in the order desired.
If you have no control over the response that is sent you will have to parse the JSON yourself at least for the ordering.
When you'r creating an NSDictionary, the order will not be the same. I often recognized that dictionaries get ordered by key-name alphabetically.
But when using dictionaries the order doesn't really matter. And they shouldn't!
As the previous answers mentions dictionaries are by nature without order, but you can find here a nice class of OrderedDictionary:
http://www.cocoawithlove.com/2008/12/ordereddictionary-subclassing-cocoa.html
http://projectswithlove.com/projects/OrderedDictionary.zip
I am reading on objective-c (a nerd ranch book), and I can't help thinking about this question: How do I decide which collection type, NSArray or NSDictionary (both with or w/o their mutable subclasses), to use when reading content from URL?
Let's say am reading JSON data from a PHP script (a scenario am dealing with), which to use? I know it is stated in many references that it depends on structure of data (i.e. JSON), but could a clear outline of the two structures be outlined?
Thank you all for helping :)
NSArray is basically just an ordered collection of objects, which can be accessed by index.
NSDictionary provides access to its objects by key(typically NSStrings, but could be any object type like hash table).
To generate an object graph from a JSON string loaded via a URL, you use NSJSONSerialization, which generates an Objective-C object structure. The resulting object depends on the JSON string. If the top-level element in your JSON is an array (starts with "["), you'll get an NSArray. If the top-level element is a JSON object (starts with "{"), you'll get an NSDictionary.
You want to use NSArray when ever you have a collection of the same type of objects, and NSDictionary when you have attributes on an object.
If you have, lets say a person object containing a name, a phone number and an email you would put it in a dictionary.
Doing so allows the order of the values to be random, and gives you a more reliable code.
If you want to have more then one person you can then put the person objects in an array.
Doing so allow you to iterate the user objects.
"withContentOfURL" or "withContentOfFile" requires the data in the URL or the file to be in a specific format as it is required by Cocoa. JSON is not that format. You can only use these methods if you wrote the data to the file or the URL yourself in the first place, with the same data. If you write an NSArray, you can read an NSArray. If you write an NSDictionary, you can read an NSDictionary. Everything else will fail.
In my project I have to load a number of json files. I parse them with JSONKit and after every single parsing with
NSMutableDictionary *json = [myJSON objectFromJSONString];
I add them to an array like:
[self.themeArray addObject:json];
This works fine so far. Now I need to pass the dictionaries arround between views. Works so far as well, but I need to add few more objects to the dictionary object-> json. Even it I declared json as NSMutableDictionary it does not allow me to add objects as it seems the JSONKit parser creates non-mutable dictionaries.
I was thinking about creating an object which contains the json dictionary and my additional data side by side so I wouldn´t have to change the json dictionary. I could even change it to NSDictionary because there is no need to change it. But that seems somehow not-elegant to me.
Do you have any idea how I can solve this issue without changing the JSONKit lib?
Thanks in advance!
EDIT
i just tried after changing my code to
NSMutableDictionary *json = [[myJSON objectFromJSONString] mutableCopy];
something like this
[[self.theme objectForKey:#"theme"] setObject:sender forKey:#"sender"];
[[self.theme objectForKey:#"theme"] setValue:sender forKey:#"sender"];
Xcode throws an exception:
* Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '* -[JKDictionary setObject:forKey:]: mutating method sent to immutable object'
I assume that´s due to the fact there are still nested dictionaries in the superior dictionary. Then i would have to interate through my json object to copy all dictionaries to mutable dictionaries, right?
Perhaps it's better to switch to NSJSONSerialization as suggested by Guillaume.
EDIT
I just tried something like this
[self.theme setValue:sender forKey:#"sender"];
And it works now! It was as i assumend. Only the json object was copied to a mutable object. Probably obvious to you, it was not to me.
Thank you all for your help!
EDIT
Finally i changed my code again after i could not manage to change all objects deep inside my dictionary data to mutable objects. I threw out JSONKit and use now NSJSONDeserialization as recommendet here with the option NSJSONReadingMutableContainers. My code looks now like this and all containers (arrays and dictionaries) are mutable deep inside too. That makes me happy! ;-)
NSMutableDictionary *json = [NSJSONSerialization JSONObjectWithData:myJSON options:NSJSONReadingMutableContainers error:&jsonParsingError];
You can always create mutable versions of objects from their non-mutable counterparts by copying them.
NSMutableDictionary* json = [[myJSON objectFromJSONString] mutableCopy];
It is not optimal, but copying smaller dictionaries does is usually not noticable from a performance point of view.
Even it I declared json as NSMutableDictionary it does not allow me to add objects as it seems the JSONKit parser creates non-mutable dictionaries.
What type the variable is declared at means nothing. You could have declared json as NSNumber and that wouldn't make it an NSNumber.
You need to make a mutable copy of the dictionary (with mutableCopy) to get an NSMutableDictionary.
I have three ideas for your.
Create real data model objects and store them in your array. Use the JSON dictionary to init your object.
Store NSMutableDictionary objects in your array. Pass the JSON dictionary to +[NSMutableDictionary dictionaryWithDictionary:] to init the NSMutableDictionary. Others have suggested calling -[NSDictionary mutableCopy] on the JSON dictionary to do the same thing.
Create a category based on NSDictionary that stores the additional data.
NOTES:
Generally creating classes to represent your data is considered the best option, but it is also the most amount of up front work. Basically you are trading more up front work against more maintenance work as you try to keep up maintaining the dictionaries.
Storing mutable dictionary is exactly what you seem to be asking for, but it may be lots of works to find all the places where JSON dictionaries are added to the array and replacing them with the new call.
Creating a category for NSDictionary means you shouldn't need to change any of your current code, but it requires maintainers to understand how you have enhanced NSDictionary. In addition, it will help separate your changes from the original parsed JSON. You can use associated objects to store the data.