Pure C++ equivalent for NSURLConnection and NSURLRequest

Question

I am porting a game using native C++ for Android. I need to know which method I should use to achieve the same functionality as NSURLConnection and NSURLRequest in only C++. Also how to get all the following delegate functions implemented for C++.

-(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

Please advise.

Answer 1

There is no way to implement Objective-C delegate methods in C++ directly. The best you can really hope to do is to use Objective-C++ to make a C++ object with an instance variable that is an Objective-C object whose sole purpose is to be the NSURLConnection delegate and forward those method calls to the owning C++ object. The C++ object should own/retain the Objective-C object, and be responsible for plugging it in as the delegate of the NSURLConnection object.

An extremely naive implementation of the above described pattern might look like this:

URLConnection.h

#ifndef __Cplusplus__URLConnection__
#define __Cplusplus__URLConnection__

#include <string>

class URLConnection
{
public:
    URLConnection(std::string url);
    ~URLConnection();

    void DidReceiveResponse(const void* response);
    void DidReceiveData(const void* data);
    void DidFailWithError(std::string error);
    void DidFinishLoading();

    void* mNSURLConnection;
    void* mDelegate;
};

#endif /* defined(__Cplusplus__URLConnection__) */

URLConnection.mm

#include "URLConnection.h"

@interface PrivateNSURLConnectionDelegate : NSObject <NSURLConnectionDelegate>
{
    URLConnection* mParent;
}
- (id)initWithParent: (URLConnection*) parent;
@end

@implementation PrivateNSURLConnectionDelegate

- (id)initWithParent: (URLConnection*) parent
{
    if (self = [super init])
    {
        mParent = parent;
    }
    return self;
}

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    mParent->DidReceiveResponse(response);
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    mParent->DidReceiveResponse(data.bytes);
}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    mParent->DidFailWithError(std::string([[error description]UTF8String]));
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    mParent->DidFinishLoading();
}

@end


URLConnection::URLConnection(std::string url)
{
    this->mDelegate = [[PrivateNSURLConnectionDelegate alloc] initWithParent: this];
    NSURLRequest* req = [NSURLRequest requestWithURL: [NSURL URLWithString: [NSString stringWithUTF8String: url.c_str()]]];
    this->mNSURLConnection = [[NSURLConnection alloc] initWithRequest: req delegate: (id)this->mDelegate];
}

URLConnection::~URLConnection()
{
    [(NSObject*)this->mNSURLConnection release];
    [(NSObject*)this->mDelegate release];
}

void URLConnection::DidReceiveResponse(const void* response)
{
    // Do something...
}
void URLConnection::DidReceiveData(const void* data)
{
    // Do something...

}
void URLConnection::DidFailWithError(std::string error)
{
    // Do something...
}

void URLConnection::DidFinishLoading()
{
    // Do something...
}

At the end of the day, NSURLConnection is an Objective-C object. There's no way to interact with it without using Objective-C.