App crashing with exception: -[NSConcreteMutableData _fastCharacterContents] - ios

Question

I am trying to share data with facebook. I am able to share data except image stored locally in iPhone memory. But when I try to share image stored locally with parameter #"source" my app gets terminated with error "[NSConcreteMutableData _fastCharacterContents]".
For sharing a local image I am converting it into NSData as required by #"source" parameter.
NSData *data = [NSData dataWithContentsOfURL:localUrl];
__block ACAccount *facebookAccount = nil;
ACAccountType *facebookAccountType = [self.accountStore accountTypeWithAccountTypeIdentifier:ACAccountTypeIdentifierFacebook];
// Specify App ID and permissions
NSDictionary *options = #{
ACFacebookAppIdKey: #"xxxxxxxxxxxxxx",
ACFacebookPermissionsKey: #[#"email"],
ACFacebookAudienceKey: ACFacebookAudienceEveryone
}; // basic read permissions
[self.accountStore requestAccessToAccountsWithType:facebookAccountType
options:options completion:^(BOOL granted, NSError *e)
{
if (granted) {
// Now that you have publish permissions execute the request
NSDictionary *options2 = #{
ACFacebookAppIdKey: #"xxxxxxxxxxxxxx",
ACFacebookPermissionsKey: #[#"publish_stream", #"publish_actions"],
ACFacebookAudienceKey: ACFacebookAudienceFriends
};
[self.accountStore requestAccessToAccountsWithType:facebookAccountType options:options2 completion:^(BOOL granted, NSError *error) {
if (granted) {
NSArray *accounts = [self.accountStore accountsWithAccountType:facebookAccountType];
facebookAccount = [accounts lastObject];
/*NSDictionary *parameters = #{#"message": #"This is a test",
#"name": #"Sharing Tutorial",
#"caption": #"Build great social apps and get more installs.",
#"description": #"Allow your users to share stories on Facebook from your app using the iOS SDK.",
#"link": #"https://developers.facebook.com/docs/ios/share/",
#"source":data};*/
NSMutableDictionary *parameters = [NSMutableDictionary dictionaryWithObjectsAndKeys:
#"My hat image", #"message", data, #"source", nil];
NSURL *feedURL = [NSURL URLWithString:#"https://graph.facebook.com/me/photos"];
SLRequest *feedRequest = [SLRequest
requestForServiceType:SLServiceTypeFacebook
requestMethod:SLRequestMethodPOST
URL:feedURL
parameters:parameters];
NSLog(#"AnythingHere?");
[feedRequest setAccount:facebookAccount];
[feedRequest performRequestWithHandler:^(NSData *responseData,
NSHTTPURLResponse *urlResponse, NSError *error)
{
// Handle response
NSLog(#"%#%#", error,urlResponse);
NSDictionary *response = [NSJSONSerialization JSONObjectWithData:responseData options:kNilOptions error:nil];
NSLog(#"Facebook Response : %#",response);
}];
}
else {
NSLog(#"Access denied 2");
NSLog(#"%#", [error description]);
}
}];
} else {
NSLog(#"Error: %#", [e description]);
NSLog(#"Access denied");
}
}];
What can be the reason behind this error?

Answer 1

This is just an educated guess because I've never used the Social framework, but it's too long for a comment.
Judging by this answer I would say that you are using SLRequest wrong. I'm pretty sure that the exception comes from your data object which is interpreted as a NSString (or NSURL).
Maybe you should use addMultipartData:withName:type:filename: to attach your photo to the request.
NSMutableDictionary *parameters = [NSMutableDictionary dictionaryWithObjectsAndKeys:
#"My hat image", #"message", nil];
NSURL *feedURL = [NSURL URLWithString:#"https://graph.facebook.com/me/photos"];
SLRequest *feedRequest = [SLRequest
requestForServiceType:SLServiceTypeFacebook
requestMethod:SLRequestMethodPOST
URL:feedURL
parameters:parameters];
[feedRequest addMultipartData:data
withName:#"source"
type:#"multipart/form-data"
filename:#"Test Image"];
which is basically the same code as another answer

Answer 2

please recheck your parameters formation.
and convert your image in following formate(Base64)
NSData *rep = UIImagePNGRepresentation(img);
NSLog(#"Rep: %#", rep);
NSString *base64 = [rep encodeBase64];
NSLog(#"Base 64 is a %#", NSStringFromClass([base64 class]));
self.somestring = [#"hardcodedstring" stringByAppendingString:base64]; //encodeBase64 encodes it to base64