Consider a Core Data database containing Elements where each Element has a property called symbol, and the question is the most succinct method of obtaining an NSArray of each of the symbols. This can be accomplished with something along the lines of
-(NSArray*)symbolsInDatabase {
ENTRY_LOG;
NSError* err;
NSFetchRequest* request = [NSFetchRequest fetchRequestWithEntityName:#"Element"];
request.resultType = NSDictionaryResultType;
request.propertiesToFetch = [NSArray arrayWithObject:#"symbol"];
NSArray* arrayOfDictionaries = [self.database.managedObjectContext executeFetchRequest:request error:&err];
NSMutableArray* symbols = [[NSMutableArray alloc]initWithCapacity:[arrayOfDictionaries count]];
for (NSDictionary* d in arrayOfDictionaries) {
[symbols addObject:[d objectForKey:#"symbol"]];
}
EXIT_LOG;
return symbols;
}
Yet there is a nagging feeling I'm missing something, and that I can be using -(NSArray*)filteredArrayUsingPredicate in some clever manner rather than iterating over the array of dictionaries and extracting the object for the symbol key.
Any thoughts on how to make this cleaner?
Indeed, the valueForKeyPath selector:
NSArray *symbols = [arrayOfDictionaries valueForKeyPath:#"#unionOfObjects.symbol"];
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);
Ok, im a bit lost with this one, i am currently trying to run a background core data operation using a second ManagedObjectContext with its type set to NSPrivateQueueConcurrencyType and failing miserably with the above error.
I have a custom subclass of NSOperation, which is being passed an NSArray of strings, and the PersistentStoreCoordinator from the main thread, it then creates its own ManagedObjectContext, runs a query and performs and operation.
Here is the code from the class:
//
// ProcessProfanity.m
// Hashtag Live Desktop
//
// Created by Gareth Jeanne on 24/03/2014.
// Copyright (c) 2014 Gareth Jeanne. All rights reserved.
//
#import "ProcessProfanity.h"
#import "Tweet.h"
static const int ImportBatchSize = 250;
#interface ProcessProfanity ()
#property (nonatomic, copy) NSArray* badWords;
#property (nonatomic, strong) NSManagedObjectContext* backgroundContext;
#property (nonatomic, strong) NSPersistentStoreCoordinator* persistentStoreCoordinator;
#end
#implementation ProcessProfanity
{
}
- (id)initWithStore:(NSPersistentStoreCoordinator*)store badWords:(NSArray*)words
{
self = [super init];
if(self) {
self.persistentStoreCoordinator = store;
self.badWords = words;
}
return self;
}
- (void)main
{
_backgroundContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
_backgroundContext.persistentStoreCoordinator = [self persistentStoreCoordinator];
_backgroundContext.undoManager = nil;
[_backgroundContext performBlockAndWait:^
{
[self import];
}];
}
- (void)import
{
//Create new fetch request
NSFetchRequest *request = [[NSFetchRequest alloc] init];
//Setup the Request
[request setEntity:[NSEntityDescription entityForName:#"Tweet" inManagedObjectContext:self.backgroundContext]];
NSError *error = nil;
//Create an array from the returned objects
NSArray* tweetsToProcess = [self.backgroundContext executeFetchRequest:request error:&error];
NSAssert2(tweetsToProcess != nil && error == nil, #"Error fetching events: %#\n%#", [error localizedDescription], [error userInfo]);
for (Tweet* tweetToCheck in tweetsToProcess){
__block NSString *result = nil;
[self.badWords indexOfObjectWithOptions:NSEnumerationConcurrent
passingTest:^(NSString *obj, NSUInteger idx, BOOL *stop)
{
if (tweetToCheck){
if ([tweetToCheck.text rangeOfString:obj].location != NSNotFound)
{
result = obj;
*stop = YES;
//return YES;
}
}
return NO;
}];
if (!result){
//DDLogVerbose(#"The post does not contain any of the words from the naughty list");
if(tweetToCheck){
tweetToCheck.profanity = [NSNumber numberWithBool:false];
}
}
else{
if(tweetToCheck){
//DDLogVerbose(#"The string contains '%#' from the the naughty list", result);
tweetToCheck.profanity = [NSNumber numberWithBool:true];
}
}
}
[self.backgroundContext save:NULL];
}
#end
And this is how i am calling it:
-(void)checkForProfanity{
if(!self.operationQueue){
self.operationQueue = [[NSOperationQueue alloc] init];
}
NSArray* termsToPass = [self.filterTerms copy];
ProcessProfanity* operation = [[ProcessProfanity alloc] initWithStore:self.persistentStoreCoordinator badWords:termsToPass];
[self.operationQueue addOperation:operation];
}
Edit 1
The specific line i seem to be getting the error on, or at least where Xcode is breaking is:
if ([tweetToCheck.text rangeOfString:obj].location != NSNotFound)
I have managed to narrow this down a bit, the NSArray that contains the list of terms to search the strings for is potentially quite large, possibly over a 1,000 NSStrings. If i test with an array of that size, i get the issue. However if i reduce the array to around 15 NSStrings, i do not get the error, so i don't think this is necessarily a thread related issue, i'm wondering if the array is getting released in the main thread. I have modified the code to make a deep copy, and then a __block copy as follows, but it doesn't seem to have helped.
self.badWords = [[NSArray alloc] initWithArray:words copyItems:YES];
and
for (Tweet* tweetToCheck in tweetsToProcess){
__block NSArray *array = [[NSArray alloc] initWithArray:self.badWords copyItems:YES];
__block NSString *result = nil;
[array indexOfObjectWithOptions:NSEnumerationConcurrent
In fact, at the point where Xcode breaks, if i PO array, i get an object not found message, but if i po result, i correct get an object returned that is nil.
Edit 2
So i have made the following changes, with no change:
Made the NSArray strong rather than copy:
#property (nonatomic, strong) NSArray* badWords;
And made it a copy when allocated:
self.badWords = [[NSArray alloc] initWithArray:words copyItems:YES];
And created a local copy of the NSArray with the ___block declaration inside the actual method processing the objects:
__block NSArray *array = [[NSArray alloc] initWithArray:self.badWords copyItems:YES];
Which should surely mean it sticks around for the life of the ProcessProfanity object?
Am i wrong in expecting to be able to PO the array from the breakpoint within the block?
In this instance the error message "error: NULL _cd_rawData but the object is not being turned into a fault" indicates that you are accessing a managed object outside of its context. Basically your fetch returns all the Tweets from your persistent store as faults. Once you try and access a property on the Managed Object, Core Data will fire a fault and fetch the full object from the store.
By calling the NSArray method indexOfObjectWithOptions:passingTest: with an option of NSEnumerationConcurrent you are implying that you want to perform asynchronous execution on the elements in your array. The keyword concurrent indicates that multiple threads can be used to operate on the array elements.
In your context this means that accessing a managed object inside this block might result in accessing it on a different thread from the managed object context that owns the object. So when you access tweetToCheck.text in your conditional check - if ([tweetToCheck.text rangeOfString:obj].location != NSNotFound), under the hood Core Data is fetching that managed object from the persistent store and returning it to a thread that is not part of the managed object contexts thread.
Furthermore, it is not necessary to use the method indexOfObjectWithOptions:passingTest: since you are not actually interested in the result of this operation.
It seems to me that it might be more convenient for you to use an NSSet as you are only testing to see whether or not a given tweet word exists in your profane words. Quoting the documentation for NSSet: "You can use sets as an alternative to arrays when the order of elements isn’t important and performance in testing whether an object is contained in the set is a consideration". Clearly this seems to meet your criteria.
So your init would look like:
-(id)initWithStore:(NSPersistentStoreCoordinator*)store
badWords:(NSSet*)badWords
{
self = [super init];
if(self) {
self.persistentStoreCoordinator = store;
self.badWords = [words copy];
}
return self;
}
Since you are only interested in updating tweets that have not yet been tagged for profanity you would probably only want to fetch tweets that haven't been flagged profane:
//Create new fetch request
NSFetchRequest *request = [[NSFetchRequest alloc] init];
//Setup the Request
[request setEntity:[NSEntityDescription entityForName:#"Tweet" inManagedObjectContext:self.backgroundContext]];
[request setPredicate:[NSPredicate predicateWithFormat:#"profanity = NO"]];
Now that you have an array of tweets that are not profane you could iterate through your tweets and check each word if it contains a profane word. The only thing you will need to deal with is how to separate your tweet into words (ignoring commas and exclamation marks etc). Then for each word you are going to need to strip it of diacritics and probably ignore the case. So you would end up with someone along the lines of:
if([self.badWords containsObject:badWordString]) {
currentTweet.profanity = [NSNumber numberWithBOOL:YES];
}
Remember, you can run predicates on an NSSet so you could actually perform a case and diacritic insensitive query:
NSPredicate *searchPredicate = [NSPredicate predicateWithFormat:#"SELF = %#[cd]",wordToCheck];
BOOL foundABadWord = ([[[self.badWords filteredSetUsingPredicate:searchPredicate] allObjects] count] > 0);
Another thing you might want to consider is removing duplicate words in your tweets, you don't really want to perform the same check multiple times. So depending on how you find the performance you could place each word of your tweet into an NSSet and simply run the query on the unique words in your tweet:
if([[self.badWords intersectsSet:tweetDividedIntoWordsSet]) {
//we have a profane tweet here!
}
Which implementation you choose is up to you but assuming you are only using english in your app you are definitely going to want to run a case and diacritic insensitive search.
EDIT
One final thing to note is that no matter how much you try, people will always be the best means of detecting profane or abusive language. I encourage you to read this SO's post on detecting profanity - How do you implement a good profanity filter?
Ok, so still not quite sure what was going on, but i followed Daniels advice and re-wrote the indexOfObjectWithOptions method and now it's working. For completeness, and so it hopefully helps someone else, this is what i ended up doing.
DDLogInfo(#"Processing posts to check for bad language");
for (Tweet* tweetToCheck in tweetsToProcess){
__block NSArray *array = [[NSArray alloc] initWithArray:self.badWords copyItems:YES];
__block NSString *result = nil;
NSRange tmprange;
for(NSString *string in array) {
tmprange = [tweetToCheck.text rangeOfString:[NSString stringWithFormat:#" %# ", string]];
if (tmprange.location != NSNotFound) {
result = string;
DDLogVerbose(#"Naughty Word Found: %#", string);
break;
}
}
if (!result){
//DDLogVerbose(#"The post does not contain any of the words from the naughty list");
if(tweetToCheck){
tweetToCheck.profanity = [NSNumber numberWithBool:false];
}
}
else{
if(tweetToCheck){
//DDLogVerbose(#"The string contains '%#' from the the naughty list", result);
tweetToCheck.profanity = [NSNumber numberWithBool:true];
}
}
The JSON source formatted with jsonviewer.stack.hu:
My Parse Method (simplified):
- (void)parseMethod {
// OTHER STUFF
arrayList = [[NSMutableArray alloc] init];
NSURL *url2 = // THE URL SOURCE OF JSON OBJECT, ON A REMOTE SERVER
NSURLRequest *request2 = [NSURLRequest requestWithURL:url2 cachePolicy:NSURLRequestReloadIgnoringLocalAndRemoteCacheData timeoutInterval:5.0];
AFJSONRequestOperation *operation2 = [AFJSONRequestOperation
JSONRequestOperationWithRequest:request2
success:^(NSURLRequest *request2, NSHTTPURLResponse *response2, id JSON)
{
arrayList = [JSON objectForKey:#"list"];
// HERE I TRIED TO WRITE [arrayListPrev removeObjectAtIndex:0];
NSMutableArray *arrayList1 = [arrayList valueForKey:#"list1"];
}
failure:^(NSURLRequest *request2, NSHTTPURLResponse *response2, NSError *error2, id JSON2) {
}];
[operation2 start];
}
The problem:
After the parsing I want to remove the FIRST OBJECT of array named "list", because I must populate the rows of a UITableView with all the values of list1 in the arrays EXCEPT the first ( list array->array number 0->list1 value of 0 ). I have tried the code:
[arrayList removeObjectAtIndex:0];
In several position but app crashes with error:'-[__NSCFArray removeObjectAtIndex:]: mutating method sent to immutable object'... so what's the best way to REMOVE the FIRST object (array number 0) from that NSMutableArray *list AFTER the parsing, to ELIMINATE The list1 value of 0 object? Thanks!
In spite of you write arrayList = [[NSMutableArray alloc] init];
Here, as i guess, you assign simple immutable array instance
arrayList = [JSON objectForKey:#"list"];
You can do this instead:
arrayList = [[JSON objectForKey:#"list"] mutableCopy];
[arrayList removeObjectAtIndex:0];
The problem is that you are working with an NSArray and not an NSMutableArray. This is probably due to the fact your parser returns immutable objects. What you need to do is take that NSArray, create an NSMutableArray with it and then remove the first object
NSMutableArray *_arrayList = [NSMutableArray arrayWithArray:arrayList];
[_arrayList removeObjectAtIndex:0];
// dont forget to store your array wherever you need it
The Error shows that your array is having value of immutable type.Use a mutable copy or initialize your arrayList with -arrayWithArray: method.Hope it fixes the problem.
Note: allocate NSMutableArray to initialize with initWithCapacity method
As other's have suggested, you're working with an NSArray, which is not Mutable (Editable). I'm going to add my input though with a new function:
NSMutableArray *mutableArrayList = [arrayList mutableCopy];
This creates a mutable copy of the array.
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've done the following to put a fetched request into an array of arrays but now i don't know which methods i need to call from chcsvparser to write this into a csv file
NSArray *objectsForExport = [fetchedResultsController fetchedObjects];
NSArray *exportKeys = [NSArray arrayWithObjects:#"best_checkout", #"darts_thrown", #"high_score", #"score_100", #"score_140", #"score_180",#"three_dart_average",nil];
NSMutableArray *csvObjects = [NSMutableArray arrayWithCapacity:[objectsForExport count]];
for (NSManagedObject *object in objectsForExport) {
NSMutableArray *anObjectArray = [NSMutableArray arrayWithCapacity:[exportKeys count]];
for (NSString *key in exportKeys) {
id value = [object valueForKey:key];
if (!value) {
value = #"";
}
[anObjectArray addObject:[value description]];
}
[csvObjects addObject:anObjectArray];
}
As Johann suggests, you should use the writeToCSVFile:atomically: convenience method. However, be aware that using it as you describe in your comment is not correct.
The NSString you pass in should be the filepath you want the data writing to.
This webpage should give you the necessary information and methods when writing CSV files:
https://github.com/davedelong/CHCSVParser#readme
Hope this helps!