obj-c return block NSString to c++ after request - c++

Question

I'm trying to get this data correctly back to c++, but there are some random crashes. I want to access the data in C++. Sometimes it does, sometime it doesn't. I couldn't find a clear example on how to return this data. Here's my code:
- (NSString*) sendRequestToServer : (CLLocationCoordinate2D) location {
NSLog(#"getting geo from server %# %# ", [NSString stringWithFormat:#"%f", location.latitude],[NSString stringWithFormat:#"%f", location.longitude]);
__block long returnBytesSend = 0;
__block long returnBytesTotal = 0;
__block NSString* tempData = #"" ;
__block BOOL foundNow = false;
self.data = nil;
for (NXOAuth2Account *account in [[NXOAuth2AccountStore sharedStore] accounts]) {
NSMutableDictionary *params = [NSMutableDictionary dictionary];
[params setObject: [NSString stringWithFormat:#"%f", location.latitude] forKey: #"latitude"];
[params setObject: [NSString stringWithFormat:#"%f", location.longitude] forKey:#"longitude" ];
[params setObject: #"10" forKey: #"radius" ];
[params setObject: #"5" forKey: #"limit"];
NXOAuth2Client *client = [account oauthClient];
NXOAuth2AccessToken *tokenData = [client accessToken];
NSString * clientAccessToken = [tokenData accessToken];
NSString * clientRefreshToken = [tokenData refreshToken];
if (clientAccessToken && clientRefreshToken ){
[NXOAuth2Request performMethod:#"GET"
onResource:[NSURL URLWithString:#"http://www.server.com/list"]
usingParameters: params
withAccount:account
sendProgressHandler:^(unsigned long long bytesSend, unsigned long long bytesTotal) {
returnBytesSend = bytesSend ;
returnBytesTotal = bytesTotal;
}
responseHandler:^(NSURLResponse *response, NSData *responseData2, NSError *error){
NSLog(#"FOUND DATA");
NSRange range = [[[NSString alloc] initWithData:responseData2 encoding:NSUTF8StringEncoding] rangeOfString : #"facebook_id"];
if(range.location != NSNotFound) {
tempData = [[[NSString alloc] initWithData:responseData2 encoding:NSUTF8StringEncoding]retain];
//NSLog(#"%#", tempData);
self.data = [[tempData copy] autorelease];
foundData = true;
}
}];
}
}
return tempData;
}
I was trying to acces the data this way:
#interface oAuthView : UIWebView
#property (nonatomic, strong) __block NSString* data;
#property (nonatomic) __block BOOL foundData;
and in c++ like this:
oAuthView *getWebView;
getWebView =[[oAuthView alloc] initWithFrame:CGRectMake(10,40,300,400)];
if ([getWebView foundData] )
string dataS = string([[artPartView data] UTF8String]));