Strange NSData Output - objective-c

Question

I have some unexpected results coming from the following code:
- (NSData *)postDataWithDict:(NSDictionary *)postDict
{
// Assume key is urlValid
NSUInteger postCount = [postDict count];
NSMutableArray *buildArray = [[NSMutableArray alloc] initWithCapacity:postCount];
for (NSString *key in postDict) {
//post data is key=value&key=value&key=value...
// start with key
NSMutableString *arrayLine = [NSMutableString stringWithString:key];
[arrayLine appendString:#"="];
// analyze and then append value
id postValue = [postDict objectForKey:key];
if ([postValue isKindOfClass:[NSNumber class]]) {
NSString *valueString = [NSString stringWithFormat:#"%#",postValue];
[arrayLine appendString:valueString];
}
else if ([postValue isKindOfClass:[NSString class]]) {
NSString *urlEncodedString = [self urlEncodeValue:postValue];
[arrayLine appendString:urlEncodedString];
}
else {
NSLog(#"postKey: %#, postValue class:%#", key, [postValue class]);
NSError *jsonError = nil;
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:postValue
options:0
error:&jsonError];
if (jsonError != nil) {
NSLog(#"JSON serialization failed: %# - %#", [jsonError localizedDescription], [jsonError userInfo]);
NSLog(#"value: %#", postValue);
}
else {
// need to urlencode
NSString *stringifyJSON = [NSString stringWithUTF8String:[jsonData bytes]];
NSString *urlJSONstring = [self urlEncodeValue:stringifyJSON];
[arrayLine appendString:urlJSONstring];
}
}
[buildArray addObject:arrayLine];
}
NSString *postString = [buildArray componentsJoinedByString:#"&"];
NSData *postData = [postString dataUsingEncoding:NSUTF8StringEncoding];
//testing
NSLog(#"Post Dict: %#", postDict);
NSLog(#"Post Array: %#", buildArray);
NSLog(#"Post String: %#", postString);
NSLog(#"Post Data: %#", [NSString stringWithUTF8String:[postData bytes]]);
return postData;
}
My //testing log results:
Post Dict: {
authenticationString = b3210c0bc6d2c47f4c2f7eeea12e063d;
dataMode = updateSingle;
dateCreated = "374300293.81108";
dateModified = "374609294.313093";
dateSynced = "374610683.588062";
entityName = CommodityTypes;
myName = 21;
sortKey = 21;
username = iPhoneAdamek;
usernameString = iPhoneAdamek;
uuidKey = "53403EAE-DD4F-4226-A979-316EF7F43991";
}
Post Dict looks good. Just what I wanted.
2012-11-14 13:31:23.640 FoodyU[11393:907] Post Array: (
"myName=21",
"dataMode=updateSingle",
"dateSynced=374610683.588062",
"uuidKey=53403EAE-DD4F-4226-A979-316EF7F43991",
"sortKey=21",
"dateModified=374609294.313093",
"entityName=CommodityTypes",
"dateCreated=374300293.81108",
"authenticationString=b3210c0bc6d2c47f4c2f7eeea12e063d",
"usernameString=iPhoneAdamek",
"username=iPhoneAdamek"
)
Post Array looks good. Strings are all set to be concatenated for a HTTP POST string.
2012-11-14 13:31:23.641 FoodyU[11393:907] Post String: myName=21&dataMode=updateSingle&dateSynced=374610683.588062&uuidKey=53403EAE-DD4F-4226-A979-316EF7F43991&sortKey=21&dateModified=374609294.313093&entityName=CommodityTypes&dateCreated=374300293.81108&authenticationString=b3210c0bc6d2c47f4c2f7eeea12e063d&usernameString=iPhoneAdamek&username=iPhoneAdamek
Post String looks good. I'm ready to convert it to data to use in [NSMutableURLRequest setHTTPBody:postData].
2012-11-14 13:31:23.643 FoodyU[11393:907] Post Data: myName=21&dataMode=updateSingle&dateSynced=374610683.588062&uuidKey=53403EAE-DD4F-4226-A979-316EF7F43991&sortKey=21&dateModified=374609294.313093&entityName=CommodityTypes&dateCreated=374300293.81108&authenticationString=b3210c0bc6d2c47f4c2f7eeea12e063d&usernameString=iPhoneAdamek&username=iPhoneAdamekoneAdamek;
usernameString = iPhoneAdamek;
uuidKey = "53403EAE-DD4F-4226-A
WTF??? How did &username=iPhoneAdamek become &username=iPhoneAdamekoneAdamek;
usernameString = iPhoneAdamek;
uuidKey = "53403EAE-DD4F-4226-A?
I'm fairly new to Cocoa. Is there something wrong with:
NSData *postData = [postString dataUsingEncoding:NSUTF8StringEncoding];
or
NSLog(#"Post Data: %#", [NSString stringWithUTF8String:[postData bytes]]);

Answer 1

You shouldn't be using NSLog of NSData as,
NSLog(#"Post Data: %#", [NSString stringWithUTF8String:[postData bytes]]);
Instead use it as,
NSLog(#"Post Data: %#", [[NSString alloc] initWithData:postData encoding:NSUTF8StringEncoding]);
[NSString stringWithUTF8String:[postData bytes]] always returns unexpected results.
As per documentation for bytes,
bytes: Returns a pointer to the receiver’s contents.
And as per Apple documentation for stringWithUTF8String,
stringWithUTF8String:
Returns a string created by copying the data from a given C array of UTF8-encoded bytes.
Parameters: bytes - A NULL-terminated C array of bytes in UTF8 encoding.
So when you are using [postData bytes], it is not NULL-terminated and hence when you are using with stringWithUTF8String returns the data written in memory till it encounters a NULL-termination.