i have simple question about how to compare result of NSDictionary with integer
i print on log the data in key result its equal 0
log
2014-09-17 10:25:42.848 School Link Version 2[1027:60b] the result are 0
but when i compare it , its dosnt work
i wish know why , its simple compare
-(void) didFinish:(NSMutableData *)data{
NSDictionary *json = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
NSLog(#"the result are %#",json[#"result"]);
if (json[#"result"] == 0) {
[[self _delegate] didFailWithMessage:json[#"message"]];
return;
}
}
You compare string to int, you need to convert string value to int:
if ([json[#"result"] intValue] == 0) {
First, your code will crash if the server didn't give you a dictionary, but an array. Since it is out of your control what the server sends, your app can crash at any time. You can check that you received a dictionary by writing
if (! [json isKindOfClass:[NSDictionary class]]) { /* Handle error */ }
Once you know it's a dictionary, you need to check what kind of item you actually expect. Do you expect a string, an integer, a decimal number? You should have a spec for the JSON data. If you are not sure, or want to be flexible, both strings and numbers produce an object that will support messages like "doubleValue", "integerValue" etc. Extract the item and assign it to a pointer of a class supporting "doubleValue", for example.
NSString* result = json [#"result"];
if (! [result respondsToSelector:#selector (doubleValue)]) { /* Handle error */ }
Now you can check whether the doubleValue is equal to 0.
if ([result doubleValue] == 0.0) { ... }
intValue will fail if the value is a large integer.
integerValue is slightly better but will fail if the value is for example the number 0.3 or the string "0.3". Everything will fail if the result is a string with the contents "Hello". You also should figure out what you want to do if result == nil (there was no key "result") or if result == [NSNull null] (there was a key:value pair "result": null)
The code that you actually wrote compared the object stored at the key "result" with 0, that is with a nil pointer. The object will be nil if the JSON data doesn't contain anything under that key. For example,
if (json [#"RandomNonsenseKey"] == 0)
will most likely succeed (unless your server sent data with a key RandomNonsenseKey).
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;
}
Let's say I loaded a JSON string into an NSDictionary that had some numbers written as strings. The resulting NSDictionary might look something like this:
NSDictionary* example = #{
#"aNumber": #"1",
#"aFloat": #"2.9708",
#"aBool": #"true",
#"aNestedDict": #{
#"more": #"220",
#"evenMore": #"false",
#"anArray": #[
#"1",
#"2"
]
}
};
I want to parse the float, integer, and bool ('true', 'false', 'yes', 'no' - case insensitive) values into their respective Objective-c class types. I've looked around, but can't find any examples of built in APIs to do this.
(Enlarged since people aren't reading the question)
Am I stuck writing a recursive parser and converting each value manually, or does Apple offer a built-in API to recursively parse it for me?
There isn't an API to do it, however you can make a helper function to figure it out. The API that apple does provide however are helper functions on NSString, i.e.: .integerValue, .doubleValue, .boolValue. However not only is this limited to NSString, it's also not comprehensive / intelligent.
So if you want to parse the string into a variable of type BOOL you can do something as simple as:
- (NSNumber *)parseBool:(NSString *)value
{
if( [value caseInsensitiveCompare:#"yes"] == NSOrderedSame || [value caseInsensitiveCompare:#"true"] == NSOrderedSame )
{
return #YES;
} else if ([value caseInsensitiveCompare:#"no"] == NSOrderedSame || [value caseInsensitiveCompare:#"false"] == NSOrderedSame )
{
return #NO;
} else
{
return nil;
}
}
EDIT:
For int and double just use:
NSString *string = #"1";
NSInteger intValue = string.integerValue;
double doubleValue = string.doubleValue;
JSON supports strings, numbers with and without decimals, boolean values, null values, dictionaries and arrays. So anyone wanting to represent numbers and boolean values in JSON can just do that.
Anyone producing JSON should document what they are producing. So if they insist on representing a boolean value as a string, then they should document which possible strings will be used to represent true and false. And then it's just a matter of string comparison.
For numbers stored as string, you can use integerValue or doubleValue which works just fine for strings.
I'd like to check for an empty object (i.e. an object of an array which doesn't have a value) within an array which gets its data from a file.
As an example, if my array contains 12 objects (all NSString) and the object at index 11 doesn't return a value when its description is printed into the debug section of Xcode. I want to check if that is the case and respond accordingly. I already tried
if (!([MY_ARRAY objectAtIndex:11] == nil))
{
//Some Stuff
}
else
{
//Some other Stuff
}
which didn't work.
Any help is appreciated.
The description method is for debugging. You should not use it in your program logic. What are these objects, and what do they contain? Can you modify the objects to add an "isEmpty" property?
If you use NSNull, you'd use code like this:
NSArray *array = #{#"String", #(4), [NSNull null], #"Another string");
for (id anObject in array)
{
if (anObject =! [NSNull null]))
{
//Some Stuff
}
else
{
//Some other Stuff
}
}
You can check the length of the string: [string length] > 0
an object is an array cannot be nil, but you can use [NSNull null] which is an "object equivalent" to nil
As Jerome Diaz states, objects in an array can't be nil. The only option you have is to check the count property of the array if it reflects an expected value, or you can inspect the type/class of the object in the array. A safe way to include empty object into array is [NSNull null], but this is the task for the method that fills the array, not the one that reads it.
You can check the class type of an object in array with isKindOfClass or isMemberOfClass.
I have some JSON that comes back like this:
"items":[
{
"has_instore_image": false
}
]
If I output the value like this:
NSLog(#"has_instore_image val: %#", [item objectForKey:#"has_instore_image"]);
I get
has_instore_image val: 0
but if I test like this:
if([item objectForKey:#"has_instore_image"]==0){
NSLog(#"no, there is not an instore image");
}else{
...
It always goes to the else statement... hmmm.. How would you suggest I get the BOOL value and test? I've read through the BOOL questions here and am just confused this is not working as I'd anticipate.
thx
NSDictionary's instance method objectForKey returns an id, not a primitive value.
If it's a boolean, int, float, etc number-like value in JSON, it will serialized to an NSNumber by Apple's NSJSONSerialization class and most/all other common JSON parsers in iOS.
If you want to get the BOOL value out of it, you can do something like this:
BOOL has_instore_image = [[item objectForKey:#"has_instore_image"] boolValue];
You are comparing a pointer with an integer here
[item objectForKey:#"has_instore_image"]==0
You should use
[item objectForKey:#"has_instore_image"].integerValue==0
Also note that a BOOL of NO equals 0.
The NSLogstatement in your code prints a 0, but only because if you give NSLogan object as parameter, the objects descriptionis called.
i will suggest to hold these id type (returned from dictionary) to NSNumber .
NSNumber *boolNum=(NSNumber*)[item objectForKey:#"has_instore_image"];
after that you can get bool value from boolNum
[boolNum boolValue]
try this
if([boolNum boolValue]==NO){
NSLog(#"no, there is not an instore image");
}else
{
}
I make a request to the Instapaper API, and it's supposed to return JSON. It returns something close to JSON, but not completely, like follows:
2013-05-30 19:54:20.155 --[53078:c07] (
{
type = meta;
},
{
"subscription_is_active" = 1;
type = user;
"user_id" = --;
username = "--#gmail.com";
},
{
"bookmark_id" = 387838931;
description = "";
hash = YHwQuwhW;
"private_source" = "";
progress = 0;
"progress_timestamp" = 0;
starred = 0;
time = 1369954406;
title = "Adobe Finally Releases Kuler Color-Picking App for iPhone - Mac Rumors";
type = bookmark;
url = "http://www.macrumors.com/2013/05/30/adobe-finally-releases-kuler-color-picking-app-for-iphone/";
},
How do I then process this? Can I take it and turn it into an NSDictionary even though it doesn't seem to be valid JSON?
From Instapaper API Docs:
Instapaper strings are always encoded in UTF-8, and Instapaper expects all input to be in UTF-8.
Unless otherwise noted, output from every method is an array. The output array is returned as JSON by default.
You can specify a jsonp parameter with a callback function name, e.g. jsonp=myCallback, to use JSONP and wrap the output in a call to the specified function.
So there is no way you will get not valid JSON!
Try following code:
NSData *jsonData = [[NSString stringWithContentsOfURL:[NSURL urlWithString:#"http://your-instapeper-API-link"] encoding:NSUTF8StringEncoding error:nil] dataUsingEncoding:NSUTF8StringEncoding];
NSError *error;
id serializationJSON = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableContainers error:&error];
And then you can log what is wrong or if result is what you expect:
NSLog(#"class of JSON input: %# \n and possible error: %#",[serializationJSON class],error);
Of course you should expect Array and no error.
EDIT ... based on coment code:
Based on docs you should get Array or Dictionary. Please add this core instead your line #23 (numer from here):
if([JSON isKindOfClass:[NSDictionary class]]) {
NSDictionary *jsonDictionary = JSON;
NSLog(#"%#",[jsonDictionary allKeys]);
} else {
NSLog(#"JSON object class: %#",[JSON class]);
}
and please show us output.
One more thing:
You get array from request. Great! This is a valid JSON. So you need to debug it. As i said it's a shame is not a unlimited acccess public API, so i can look into it. But now you have to debug your result. I see in your code that you are trying to access bookmarks. So i look into Bookmarks section in docs and this is some kind of list (NSArray). So if you don't know what result you want. You should print them into log (or set a breakpoint). Replace code from my earlier update with this simple log:
NSDictionary *resultDictionary;
if([JSON isKindOfClass:[NSArray class]]) {
NSArray *jsonArray = JSON;
NSLog(#"so json is an array with %i objects",[jsonArray count]);
for(id objectInsideArr in jsonArray) {
NSLog(#"object in array [class]: %# [value]: %#",[objectInsideArr class],objectInsideArr); //if here you find NSDictionary maybe is this dictionary you are looking for. I'm not sure what it is.
if([objectInsideArr isKindOfClass:[NSDictionary class]]) {
resultDictionary = [[NSDictionary alloc] initWithDictionary:objectInsideArr];
}
}
}
If it were me I would write a custom formatter to get it into JSON format and then use NSJSONSerialization once I know it is valid. What you posted is so far from valid there is no way it would work. I'm surprised they are returning it in that format, do they provide some kind of library for consuming their services?
If you want something even simpler, I can give you my CGIJSONObject library that will handle JSON using reflection - you just need to mirror the keys in APIs with your classes andit is good to go.