NSError *error;
NSString *string = [[NSString alloc]
initWithContentsOfURL:URL
encoding:NSUTF8StringEncoding
error:&error];
When I test this on my iPhone it always works when I have wifi turned on. However when I'm on 3G I often get nil. If I try perhaps 15 times in a row (I have an update button for this) I finally get the desired result.
My question is, is this problem located at the server side or is my code unstable? Should I use a different approach to get a more secure fetch of data?
You haven't provided enough information to give anything but a vague answer, but you do have some options here.
Most importantly, you have an "error" parameter that you should be printing out the results of. There's also a slightly better API you could be using in the NSString class.
Change your code to something like this:
NSError *error = NULL;
NSStringEncoding actualEncoding;
// variable names in Objective-C should usually start with lower case letters, so change
// URL in your code to "url", or even something more descriptive, like "urlOfOurString"
NSString *string = [[NSString alloc] initWithContentsOfURL:urlOfOurString usedEncoding:&actualEncoding error:&error];
if(string)
{
NSLog( #"hey, I actually got a result of %#", string);
if(actualEncoding != NSUTF8StringEncoding)
{
// I also suspect the string you're trying to load really isn't UTF8
NSLog( #"and look at that, the actual encoding wasn't NSUTF8StringEncoding");
}
} else {
NSLog( #"error when trying to fetch from URL %# - %#", [urlOfOurString absoluteString], [error localizedDescription]);
}
I'm now using STHTTPRequest instead. I recommend this library very much, easy to use yet powerful.
Related
I am getting the error:
"A long-running Parse operation is being executed on the main thread. Break on warnParseOperationOnMainThread() to debug."
and
"Break on warnParseOperationOnMainThread() to debug."
I'm unable to locate the error within my code. Can someone please tell me what I'm doing wrong?
PFQuery *query = [PFQuery queryWithClassName:#"User"];
[query getObjectInBackgroundWithId:[[PFUser currentUser] objectId] block:^(PFObject *object, NSError *error) {
self.firstName = object[#"firstname"];
self.lastName = object[#"lastname"];
self.nameLabel.text = [[NSArray arrayWithObjects:self.firstName, self.lastName, nil] componentsJoinedByString:#" "];
}];
This is a gentle warning to the developers when they make the Parse calls that would block the main thread.
This is where you can see it all happen,, add a symbolic breakpoint on warnBlockingOperationOnMainThread only if you use a Parse API released from 2015+. Otherwise, put it on the warnParseOperationOnMainThread.
It'll break on that function while you are running your code, and will show you a stack trace which should help you to find the blocking function.
See the images below to have a better understanding.
For me this happened when I called:
[[PFUser currentUser] refresh];
The solution was to replace it with:
[[PFUser currentUser] refreshInBackgroundWithBlock:nil];
See also this answer on the Parse Help site.
It Almost happens with all Parse queries or data saving. It avoid this, there is option to perform operation in background. Actually there are two alternatives, one is to perform in background and other is perform in background with block of code.
Maybe it is a bit late, but here you go. I think the problem come from the fact that you are trying to get to objects fetch at the same time:
[[PFUser currentUser] objectId];
and:
[query getObjectInBackgroundWithId...];
It will be better to get the userId first, such as:
//First fetch and store the id in a string so you can reuse it whenever you want
NSString *userId = [PFUser currentUser].objectId;
Second:
// Do your second fetch here:
PFQuery *query = [PFQuery queryWithClassName:#"User"];
[query getObjectInBackgroundWithId:userId block:^(PFObject *object, NSError *error) {
self.firstName = object[#"firstname"];
self.lastName = object[#"lastname"];
self.nameLabel.text = [[NSArray arrayWithObjects:self.firstName, self.lastName, nil] componentsJoinedByString:#" "];
}];
Et voila!
Strange and funny think is going on
Code:
-(void)saveFile
{
NSFileManager *fileMng = [NSFileManager defaultManager];
if(![fileMng fileExistsAtPath:self.appFilesPath])
{
NSError *error = nil;
BOOL success = [fileMng createDirectoryAtPath:self.appFilesPath withIntermediateDirectories:YES attributes:nil error:&error];
if(!success)
{
NSLog([error localizedDescription]);
}
}
NSLog([NSString stringWithFormat:#"%#",self.appFilesPath]);
[fileMng createFileAtPath:self.fileFullPath contents:self.fileData attributes:nil];
[self.fileData writeToFile:self.fileFullPath atomically:YES];
}
and this line
NSLog([NSString stringWithFormat:#"%#",self.appFilesPath]);
should give me something like this
file://localhost/Users/user/Library/Application%20Support/iPhone%20Simulator/5.0/Applications/BF35B859-514B-45AA-8E3A-B2CE65BD82B6/Documents/AppFiles
Directory AppFiles should be created under ../Documents/ directory,
but it's not there...
and the nslog gives me something like this:
file://localhost/Users/user/Library/Application瑳楲杮楗桴潆浲瑡:敲敬獡e摡䕤瑮楲獥牆浯楄瑣潩慮祲:扯敪瑣潆䭲祥:汣獡s獩楋摮晏汃獡㩳氀湥瑧h畡潴敲敬獡e敳佴橢捥㩴潦䭲祥:敲潭敶扏敪瑣潆䭲祥:湩整敧噲污敵戀潯噬污敵爀浥癯䅥汬扏敪瑣s湩瑩猀慨敲䥤獮慴据e敲楧瑳牥敎睴牯䑫晥畡瑬䙳牯灁䥰㩄挀灯y摡佤橢捥㩴洀楡䉮湵汤e畢摮敬摉湥楴楦牥椀䕳畱污潔瑓楲杮:桳牡摥潃普杩牵瑡潩n潣湵牴䑹晥畡瑬潆..few more screens of this bush..帴㽻椽絩8筞㴿楩}ㅶ䀶㨰帴㽻椽絩椸㈱䀀䜢佅楐數偬楯瑮"㽻搽絤䀸㨰4㉶䀴㨰笴㴿摤㡽䀀倢剂煥敵瑳牥"ㅶ䀶㨰⌴匸㈱䀀㰢䕇协灵潰瑲摥楔敬敓獴敓癲牥牐硯䑹汥来瑡㹥"㍶䀶㨰笴㴿摤㡽㉤椴㈳瘀㘱㐺㡀ㅩ2㉶䀸㨰帴㽻搽絤䤸㈱ㅤ椶㐲瘀㈱㐺癞8ㅀ䀶㨰帴㡶ㅣ2筞硟捰损湯敮瑣潩彮㵳}ㅀ䀶㨰䀴常彻䍟剆湵潌灯紽㈱帀彻䍟剆湵潌灯紽䀸㨰4筞彟䙃畒䱮潯㵰}癞䀸㨰4ㅀ䀲㨰帴㡶瘀〲㐺㡀ㅀ䤲㘱䀀㰢华慃档䑥汥来瑡㹥"㉀䀸㨰䀴笸㴿摤ㅽ2㽻搽絤㠲㐺㽻搽絤常㉤4㽻∽慬楴畴敤搢氢湯楧畴敤搢}upport/iPhone 貌Š߈imulator/5.0/Applications/CAF90A92-5B85-4FC0-8482-3702C3E98F8D/Documents/AppFiles
when i run code second time, the if condision is skiped, but ../Documents/ directory is stil empty
来瑡㹥"㉀䀸 - i mean wtf, first time something like this,
restarting xcode, mac did't help,
simulator is all set to english,
it also happen in other projects,
keyboard setting ant nationalization looks ok,
so realy I have no clue what is wrong
any ideas?
You can not just NSLog a string. The string argument it takes is a format (like in printf) which interpeted specially. In your case, it is reading random memory because %20S means to interpret the next argument as pointer to null-terminated string of wide characters and print it right-aligned in 20 columns; and they are Chinese because most of Unicode is occupied by Chinese hieroglyphs.
This is the correct way to do it:
NSLog(#"%#", self.appFilesPath);
i have big pool of core date objects (around 10000) and there is too long time doing code according profile:
NSDate *maxExternalChangedDate = [codes valueForKeyPath:#"#max.externalChangedDate"];
is community know better way to found it?
NSString *rateSheetID = [rateSheetAndPrefix valueForKey:#"rateSheetID"];
NSFetchRequest *requestCodesForSale = [[NSFetchRequest alloc] init];
[requestCodesForSale setEntity:[NSEntityDescription entityForName:#"CodesvsDestinationsList"
inManagedObjectContext:self.moc]];
[requestCodesForSale setPredicate:[NSPredicate predicateWithFormat:#"(%K.carrier.GUID == %#)",relationshipName,carrierGUID]];
NSError *error = nil;
NSArray *codes = [self.moc executeFetchRequest:requestCodesForSale error:&error];
if (error) NSLog(#"Failed to executeFetchRequest to data store: %# in function:%#", [error localizedDescription],NSStringFromSelector(_cmd));
NSNumber *count = [codes valueForKeyPath:#"#count.externalChangedDate"];
if (count == 0) {
[requestCodesForSale release];
[pool drain], pool = nil;
return YES;
}
NSDate *maxExternalChangedDate = [codes valueForKeyPath:#"#max.externalChangedDate"];
By using NSFetchRequest and returning NSDictionaryResultType You can use NSExpressionDescription to yeild the results for functions like max() and min().
Sample Code from Apple
NSExpression *keyPathExpression = [NSExpression expressionForKeyPath:#"salary"];
NSExpression *maxSalaryExpression = [NSExpression expressionForFunction:#"max:"
arguments:[NSArray arrayWithObject:keyPathExpression]];
NSExpressionDescription *expressionDescription = [[NSExpressionDescription alloc] init];
[expressionDescription setName:#"maxSalary"];
[expressionDescription setExpression:maxSalaryExpression];
[expressionDescription setExpressionResultType:NSDecimalAttributeType];
[request setPropertiesToFetch:[NSArray arrayWithObject:expressionDescription]];
Check out this doc for more information.
Core Data Programming Guide
I have the same issue.
In theory this should work, but for me it did not.
For some reasons the query crashes with the error that the database is corrupt.
In the end I perfomed a query, where I ordered on my field DESCENDING, and using setFetchLim it:1. Its not perfect, but at least it worked.
Also I made sure the field I use has an index.
Since I have few records, this works fine.
On 30000 records, it might be a problem though.
I followed the IOS documentation, fot fatch a "max:" query, but only got "database corrupted" errors. That is the sample code from Apple fails BADLY.
Googling the internet, it seem the call to setPropertiesToFetch fails in IOS 5+ ??!
I have not found any way around that.
Using a normal query, it worked without any issue.
So I must conclude Apple code is no longer corerct.
I often use Transformable for Core Data attributes, so I can change them later.
However, it seems like, if I want to use NSPredicate to find a NSManagedObject, using "uniqueKey == %#", or "uniqueKey MATCHES[cd] %#", it's not working as it should.
It always misses matching objects, until I change the attributes of the uniqueKey of the matching object to have specific class like NSString, or NSNumber.
Can someone explain the limitation of using NSPredicate with Transformable attributes?
Note: I'm not sure when/if this has changed since 5/2011 (from Scott Ahten's accepted answer), but you can absolutely search with NSPredicate on transformable attributes. Scott correctly explained why your assumptions were broken, but if Can someone explain the limitation of using NSPredicate with Transformable attributes? was your question, he implied that it is not possible, and that is incorrect.
Since the is the first google hit for "Core Data transformable value search nspredicate" (what I searched for trying to find inspiration), I wanted to add my working answer.
How to use NSPredicate with transformable properties
Short, heady answer: you need to be smart about your data transformers. You need to transfrom the value to NSData that contains what I'll call "primitive identifying information", i.e. the smallest, most identifying set of bytes that can be used to reconstruct your object. Long answer, ...
Foremost, consider:
Did you actual mean to use a transformable attribute? If any supported data type -- even binary data -- will suffice, use it.
Do you understand what transformable attributes actually are? How they pack and unpack data to and from the store? Review Non-Standard Persistent Attributes in Apple's documentation.
After reading the above, ask: does custom code that hides a supported type "backing attribute" work for you? Possibly use that technique.
Now, past those considerations, transformable attributes are rather slick. Frankly, writing an NSValueTransformer "FooToData" for Foo instances to NSData seemed cleaner than writing a lot of adhoc custom code. I haven't found a case where Core Data doesn't know it needs to transform the data using the registered NSValueTransformer.
To proceed simply address these concerns:
Did you tell Core Data what transformer to use? Open the Core Data model in table view, click the entity, click the attribute, load the Data Model Inspector pane. Under "Attribute Type: Transformable", set "Name" to your transformer.
Use a default transformer (again, see the previous Apple docs) or write your own transformer -- transformedValue: must return NSData.
NSKeyedUnarchiveFromDataTransformerName is the default transformer and may not suffice, or may draw in somewhat-transient instance data that can make two similar objects be different when they are equal.
The transformed value should contain only -- what I'll call -- "primitive identifying information". The store is going to be comparing bytes, so every byte counts.
You may also register your transformer globally. I have to do this since I actually reuse them elsewhere in the app -- e.g. NSString *name = #"FooTrans"; [NSValueTransformer setValueTransformer:[NSClassFromString(name) new] forName:name];
You probably don't want to use transforms heavily queried data operations - e.g. a large import where the primary key information uses transformers - yikes!
And then in the end, I simply use this to test for equality for high-level object attributes on models with NSPredicates -- e.g. "%K == %#" -- and it works fine. I haven't tried some of the various matching terms, but I wouldn't be surprised if they worked sometimes, and others not.
Here's an example of an NSURL to NSData transformer. Why not just store the string? Yeah, that's fine -- that's a good example of custom code masking the stored attribute. This example illustrates that an extra byte is added to the stringified URL to record if it was a file URL or not -- allowing us to know what constructors to use when the object is unpacked.
// URLToDataTransformer.h - interface
extern NSString *const kURLToDataTransformerName;
#interface URLToDataTransformer : NSValueTransformer
#end
...
// URLToDataTransformer.m - implementation
#import "URLToDataTransformer.h"
NSString *const kURLToDataTransformerName = #"URLToDataTransformer";
#implementation URLToDataTransformer
+ (Class)transformedValueClass { return [NSData class]; }
+ (BOOL)allowsReverseTransformation { return YES; }
- (id)transformedValue:(id)value
{
if (![value isKindOfClass:[NSURL class]])
{
// Log error ...
return nil;
}
NSMutableData *data;
char fileType = 0;
if ([value isFileURL])
{
fileType = 1;
data = [NSMutableData dataWithBytes:&fileType length:1];
[data appendData:[[(NSURL *)value path] dataUsingEncoding:NSUTF8StringEncoding]];
}
else
{
fileType = -1;
data = [NSMutableData dataWithBytes:&fileType length:1];
[data appendData:[[(NSURL *)value absoluteString] dataUsingEncoding:NSUTF8StringEncoding]];
}
return data;
}
- (id)reverseTransformedValue:(id)value
{
if (![value isKindOfClass:[NSData class]])
{
// Log error ...
return nil;
}
NSURL *url = nil;
NSData *data = (NSData *)value;
char fileType = 0;
NSRange range = NSMakeRange(1, [data length]-1);
[data getBytes:&fileType length:1];
if (1 == fileType)
{
NSData *actualData = [data subdataWithRange:range];
NSString *str = [[NSString alloc] initWithData:actualData encoding:NSUTF8StringEncoding];
url = [NSURL fileURLWithPath:str];
}
else if (-1 == fileType)
{
NSData *actualData = [data subdataWithRange:range];
NSString *str = [[NSString alloc] initWithData:actualData encoding:NSUTF8StringEncoding];
url = [NSURL URLWithString:str];
}
else
{
// Log error ...
return nil;
}
return url;
}
#end
Transformable attributes are usually persisted as archived binary data. As such, you are attempting to compare an instance of NSData with an instance of NSString or NSNumber.
Since these classes interpret the same data in different ways, they are not considered a match.
you can try this way
NSExpression *exprPath = [NSExpression expressionForKeyPath:#"transformable_field"];
NSExpression *exprKeyword = [NSExpression expressionForConstantValue:nsdataValue];
NSPredicate *predicate = [NSComparisonPredicate predicateWithLeftExpression:exprPath rightExpression:exprKeyword modifier:NSDirectPredicateModifier type:NSEqualToPredicateOperatorType options:0];
So I have this piece of code :
if ([receivedPage hasPrefix:[NSString stringWithUTF8String:"\xC3\xAF\xC2\xBB\xC2\xBF"]]) // UTF-8 BOM 'EF BB BF' as UTF-16 chars
{
//DebugLog(#"converting calls list to UTF8");
receivedPage = [[[NSString alloc] initWithData:[receivedPage dataUsingEncoding:NSISOLatin1StringEncoding] encoding:NSUTF8StringEncoding] autorelease];
}
However sometimes when the if is true the receivedPage becomes null. why would this happen?
The received page is the returned value of this function:
NSURLResponse * response;
NSData * result = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:error];
if ([result length] > 0)
return [[[NSString alloc] initWithBytes: (const void*)[result bytes] length:[result length] encoding: encoding] autorelease];
else
{
if (error && *error)
DebugLog(#"URL request got error: %#",*error);
return nil;
}
The encoding here is NSISOLatin1StringEncoding (don't know why ,I'm debugging someone else's code).
Any idea why this would happen?
It looks like you're trying to treat strings (objects containing characters) as data (objects containing bytes). Keep the data you received from the connection, and check for the UTF-8 BOM (the proper three-byte version) in it, then use either NSUTF8StringEncoding or NSISOLatin1StringEncoding based on whether you find it.
Or, just use UTF-8 conditionally, if you can fix the server to do that as well.
Also, you should probably switch this code to use the NSURLConnection asynchronously. If the user's internet connection is slow, you're hanging your app here. Doing it asynchronously lets you keep the UI running, display progress if appropriate, and enable the user to cancel.