mixing objective-c and c++

Question

Level 1

4 points

mixing objective-c and c++

Hello,
I'm trying to write a class in c++ that needs to implement some objective-c methods. I read here, that it's possible: http://www.mactech.com/articles/mactech/Vol.13/13.03/CandObjectiveCCompared/ (at the end of the document)

However, I get this error: 'error: expected unqualified-id before '-' token' at this line
+- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response+

Here's the url_connection.h

#ifndef URL_CONNECTIONH
#define URL_CONNECTIONH

#include "debug.h"

class URL_Connection
{
private:
NSData *receivedData;
NSURL *url;
NSURLRequest *theRequest;
NSURLConnection *theConnection;

public:

URL_Connection();
~URL_Connection();

};

+- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response+
{
// this method is called when the server has determined that it
// has enough information to create the NSURLResponse
// it can be called multiple times, for example in the case of a
// redirect, so each time we reset the data.
// receivedData is declared as a method instance elsewhere
[receivedData setLength:0];
}

#endif

I really have no ideea how to fix this and couldn't find something similar on the web. What am I doing wrong?

Please advice,
Thanks

Posted on Nov 9, 2008 5:53 AM

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Answer 1

xnav

Level 5

7,089 points

Nov 9, 2008 7:40 AM in response to Etek

For this forum format your code like this:


your code

At any rate it looks as if the line after '~URL_Connection();', the '};' should be '}'.

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Answer 2

Etek Author

Level 1

4 points

Nov 9, 2008 7:54 AM in response to xnav

Thanks, but the ; after } for a class is mandatory.

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Answer 3

orangekay

Level 5

4,085 points

Nov 9, 2008 9:14 AM in response to Etek

You cannot define an Objective-C method outside of an Objective-C class.

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Answer 4

Etek Author

Level 1

4 points

Nov 9, 2008 9:20 AM in response to orangekay

So, best option will be to write a objective-c class to handle this, instead of c++?

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Answer 5

orangekay

Level 5

4,085 points

Nov 9, 2008 10:42 AM in response to Etek

That would be the only option unless you want to get extremely familiar with the runtime implementation.

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Answer 6

Etek Author

Level 1

4 points

Nov 9, 2008 1:54 PM in response to orangekay

Ok, so I painfully written an objective-c class. The only thing remaining is, how do I make this class be a delegate in order to receive messages?
I hope this is the problem, because none of the methods below is called.


- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response;
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data; 
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error;
- (void)connectionDidFinishLoading:(NSURLConnection *)connection;

Thank you.

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Answer 7

etresoft

Level 8

47,108 points

Nov 9, 2008 5:27 PM in response to Etek

Cocoa is only going to talk to Objective-C. There is no way around that. You can create a simple Objective-C class derived from NSObject and make it a delegate of anything. How to assign that delegate depends on the context. If it is a user interface object you can do it through Interface Builder. If not, you'll have to look for some sort of "setDelegate" method.

Now, you can mix Objective-C and C++ very easily. Just use .mm Objective-C++ files. Your Cocoa-facing interface will always have to be Objective-C++, but those Objective-C++ methods can simply call an instance variable that is a pointer to a C++ object.

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Answer 8

Etek Author

Level 1

4 points

Nov 10, 2008 4:22 AM in response to etresoft

Thank you for your response.
I could not find any decent documentation and proper examples on the web for how to create a delegate.

Any good sites or books about objective-c that you can recommend?

Thank you

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Answer 9

orangekay

Level 5

4,085 points

Nov 10, 2008 7:15 AM in response to Etek

Etek wrote:
Thank you for your response.
I could not find any decent documentation and proper examples on the web for how to create a delegate.

Then you didn't look very hard.

http://developer.apple.com/qa/qa2007/qa1554.html

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Answer 10

Etek Author

Level 1

4 points

Nov 10, 2008 8:11 AM in response to orangekay

How does that help me?
There's nothing there about delegates that don't need a nib file. The messages required have nothing to do with a window.

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Answer 11

orangekay

Level 5

4,085 points

Nov 10, 2008 8:23 AM in response to Etek

Etek wrote:
There's nothing there about delegates that don't need a nib file.

You'd get a lot farther if you actually read the words. Since you seem to be attempting to use the URL loading system here, the associated documentation very clearly shows you how to specify your delegate object when you create the connection via initWithRequest:

http://developer.apple.com/documentation/Cocoa/Conceptual/URLLoadingSystem/Tasks /UsingNSURLConnection.html#//apple_ref/doc/uid/20001836

Notice the second parameter is named "delegate."

http://developer.apple.com/documentation/Cocoa/Reference/Foundation/Classes/NSUR LConnectionClass/Reference/Reference.html#//appleref/doc/uid/20001697-BAJDDIDG

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Answer 12

Etek Author

Level 1

4 points

Nov 10, 2008 8:54 AM in response to orangekay

Let me put it more clearly.
I already did that. If I take all that and put it in let's say myAppdelegate.m, it works.
If I put it in my class, they don't work anymore.

How do I make my class receive those messages? What am I doing wrong?


-(void) connect
{
 {
 url = [NSURL URLWithString: @"http://www.google.com" ]; 
 theRequest=[NSURLRequest requestWithURL : url
 cachePolicy : NSURLRequestReloadIgnoringCacheData
 timeoutInterval : 60.0];
 // create the connection with the request
 // and start loading the data
 theConnection=[[NSURLConnection alloc] initWithRequest:theRequest delegate:self];
 if (theConnection)
 {
 // Create the NSMutableData that will hold
 // the received data
 // receivedData is declared as a method instance elsewhere
 receivedData=[[NSMutableData data] retain];
 isConnected = true;
 }
 else
 {
 // inform the user that the download could not be made
 isConnected = false;
 }
 }
 }

I tried using setDelegate and stuff, none of it works. Obviously I'm doing something wrong and I haven't found an actual complete example of a working class to go from there, only bits and pieces and I can't put together.

Message was edited by: Etek

Message was edited by: Etek

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Answer 13

orangekay

Level 5

4,085 points

Nov 10, 2008 9:10 AM in response to Etek

You would have to instantiate an object of your class' type and pass it in rather than self.

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Answer 14

etresoft

Level 8

47,108 points

Nov 10, 2008 11:34 AM in response to Etek

Perhaps you should post your entire class, including all the delegate methods. What you are doing looks correct and is identical to Apple's NSURLConnection example. It should work fine.

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Answer 15

Etek Author

Level 1

4 points

Nov 10, 2008 1:18 PM in response to etresoft

Ok, here goes:

url_connection.h


@interface URL_Connection : NSObject
{
 NSMutableData *receivedData;
 NSURL *url;
 NSURLRequest *theRequest;
 NSURLConnection *theConnection;
 NSError *theError;
 
 bool _isConnected;
 bool _isFinished;
 
 id _delegate;
}
- (id) delegate;
- (void) setDelegate:(id)newDelegate;
- (void) connect;
- (bool) isConnected;
- (bool) isFinished;
- (NSError*) getError;
- (int) getDataSize;
- (unsigned char*) getData;
//I understood these do not necesarily have to be here, but I put them to avoid confusion in the future
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response;
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data; 
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error;
- (void)connectionDidFinishLoading:(NSURLConnection *)connection; 
@end

url_connection.m


#import "URL_Connection.h"
@implementation URL_Connection
- (id)init
{
 if (self = [super init])
 {
 _isConnected = false;
 _isFinished = false;
 }
 return self;
}
- (id)delegate
{
 return _delegate;
}
- (void)setDelegate:(id)newDelegate
{
 _delegate = newDelegate;
}
 
-(void) connect
{
 {
 url = [NSURL URLWithString: @"http://www.google.com" ]; 
 
 theRequest=[NSURLRequest requestWithURL : url
 cachePolicy : NSURLRequestReloadIgnoringCacheData
 timeoutInterval : 60.0];
 
 // create the connection with the request
 // and start loading the data
 theConnection=[[NSURLConnection alloc] initWithRequest:theRequest delegate:self];
 
 if (theConnection)
 {
 // Create the NSMutableData that will hold
 // the received data
 // receivedData is declared as a method instance elsewhere
 receivedData=[[NSMutableData data] retain];
 _isConnected = true;
 }
 else
 {
 // inform the user that the download could not be made
 _isConnected = false;
 }
 }
 }
- (bool) isConnected
{
 return _isConnected;
}
- (NSError*) getError
{
 return theError;
}
- (bool) isFinished
{
 return _isFinished;
}
- (unsigned char*) getData
{
 int urlLength = [receivedData length];
 unsigned char *downloadBuffer;
 
 downloadBuffer = (unsigned char*) malloc (urlLength);
 
 [receivedData getBytes: (unsigned char*)downloadBuffer];
 
 return downloadBuffer;
}
- (int) getDataSize
{ 
 return [receivedData length];
}
 
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response 
{ 
 // this method is called when the server has determined that it 
 // has enough information to create the NSURLResponse 
 // it can be called multiple times, for example in the case of a 
 // redirect, so each time we reset the data. 
 // receivedData is declared as a method instance elsewhere 
 [receivedData setLength:0]; 
}
 
 
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data 
{ 
 // append the new data to the receivedData 
 // receivedData is declared as a method instance elsewhere 
 [receivedData appendData:data]; 
} 
 
 
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error 
{ 
 // release the connection, and the data object
 [connection release]; 
 // receivedData is declared as a method instance elsewhere 
 [receivedData release]; 
 // inform the user 
 NSLog(@"Connection failed! Error - %@ %@", 
 [error localizedDescription], 
 [[error userInfo] objectForKey:NSErrorFailingURLStringKey]); 
} 
 
- (void)connectionDidFinishLoading:(NSURLConnection *)connection 
{ 
 // do something with the data 
 // receivedData is declared as a method instance elsewhere 
 NSLog(@"Succeeded! Received %d bytes of data",[receivedData length]); 
 // release the connection, and the data object 
 
 _isFinished = true;
 
}
- (void) dealloc
{
 NSNotificationCenter *nc = [NSNotificationCenter defaultCenter];
 
 if (_delegate)
 [nc removeObserver:_delegate name:nil object:self];
 
 [super dealloc];
//there's more to be released here
}
@end

url_connection object initialization


 URL_Connection *connection = [[URL_Connection alloc] init];

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