ARURLOperation -> NSOperation subclass. NSURLRequest. NSURLConnection. NSURLResponse. Response NSData. NSError. KVO. NSThread. NSRunLoop.

ARURLOperation.h

//
//  ARURLOperation.h
//  ARURLOperation
//
//  Created by alexruperez on 13/1/15.
//
//

#import <Foundation/Foundation.h>

@interface ARURLOperation : NSOperation <NSURLConnectionDataDelegate, NSSecureCoding, NSCopying>

@property (nonatomic, strong, readonly) NSURLRequest *request;

@property (nonatomic, strong, readonly) NSURLResponse *response;

@property (nonatomic, strong, readonly) NSData *responseData;

@property (nonatomic, strong, readonly) NSError *error;

+ (instancetype)operationWithRequest:(NSURLRequest *)request;

- (instancetype)initWithRequest:(NSURLRequest *)request NS_DESIGNATED_INITIALIZER;

@end

ARURLOperation.m

//
//  ARURLOperation.m
//  ARURLOperation
//
//  Created by alexruperez on 13/1/15.
//
//

#import "ARURLOperation.h"

@interface ARURLOperation ()
{
    BOOL _executing;
    BOOL _finished;
}

@property (nonatomic, strong, readwrite) NSURLConnection *connection;

@property (nonatomic, strong, readwrite) NSMutableData *responseMutableData;

@property (nonatomic, strong, readwrite) NSRecursiveLock *lock;

@end

@implementation ARURLOperation

- (void)networkRequestThreadEntryPoint:(id)__unused object
{
    @autoreleasepool
    {
        [NSThread currentThread].name = [NSString stringWithFormat:@"%@Thread", NSStringFromClass(self.class)];
        
        NSRunLoop *runLoop = NSRunLoop.currentRunLoop;
        [runLoop addPort:NSMachPort.port forMode:NSDefaultRunLoopMode];
        [runLoop run];
    }
}

- (NSThread *)networkRequestThread
{
    static NSThread *_networkRequestThread = nil;
    static dispatch_once_t oncePredicate;
    dispatch_once(&oncePredicate, ^{
        _networkRequestThread = [[NSThread alloc] initWithTarget:self selector:@selector(networkRequestThreadEntryPoint:) object:nil];
        [_networkRequestThread start];
    });
    
    return _networkRequestThread;
}

+ (instancetype)operationWithRequest:(NSURLRequest *)request
{
    return [[self alloc] initWithRequest:request];
}

- (instancetype)init
{
    return [self initWithRequest:nil];
}

- (instancetype)initWithRequest:(NSURLRequest *)request
{
    NSParameterAssert(request);
    
    self = [super init];
    
    if (self)
    {
        _executing = NO;
        _finished = NO;
        _request = request;
        
        self.lock = NSRecursiveLock.new;
        self.lock.name = [NSString stringWithFormat:@"%@Lock", NSStringFromClass(self.class)];
        self.name = NSStringFromClass(self.class);
    }
    
    return self;
}

- (NSData *)responseData
{
    return [NSData dataWithBytes:self.responseMutableData.bytes length:self.responseMutableData.length];
}

- (BOOL)isAsynchronous
{
    return YES;
}

- (BOOL)isExecuting
{
    return _executing;
}

- (BOOL)isFinished
{
    return _finished;
}

- (NSString *)description
{
    [self.lock lock];
    NSString *description = [NSString stringWithFormat:@"<%@: %p, cancelled: %@ request: %@, response: %@>", NSStringFromClass(self.class), self, (self.isCancelled ? @"YES" : @"NO"), self.request, self.response];
    [self.lock unlock];
    return description;
}

- (void)start
{
    [self.lock lock];
    
    if (self.isCancelled)
    {
        [self willChangeValueForKey:@"isFinished"];
        
        _finished = YES;
        
        [self didChangeValueForKey:@"isFinished"];
        
        return;
    }
    else if (self.isReady)
    {
        [self willChangeValueForKey:@"isExecuting"];
        
        [self performSelector:@selector(main) onThread:self.networkRequestThread withObject:nil waitUntilDone:NO modes:@[NSRunLoopCommonModes]];
        
        _executing = YES;
        
        [self didChangeValueForKey:@"isExecuting"];
    }
    
    [self.lock unlock];
}

- (void)main
{
    [self.lock lock];
    
    if (!self.isCancelled && [NSURLConnection canHandleRequest:self.request])
    {
        self.responseMutableData = NSMutableData.new;

        self.connection = [[NSURLConnection alloc] initWithRequest:self.request delegate:self startImmediately:NO];

        [self.connection scheduleInRunLoop:NSRunLoop.currentRunLoop forMode:NSRunLoopCommonModes];
        
        [self.connection start];
    }
    
    [self.lock unlock];
}

- (void)completeOperation
{
    [self willChangeValueForKey:@"isFinished"];
    [self willChangeValueForKey:@"isExecuting"];
    
    _executing = NO;
    _finished = YES;
    
    [self didChangeValueForKey:@"isExecuting"];
    [self didChangeValueForKey:@"isFinished"];
}

# pragma mark - NSURLConnectionDataDelegate

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    if (!self.isCancelled)
    {
        [self.responseMutableData appendData:data];
        return;
    }
    
    [self completeOperation];
}

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    if (!self.isCancelled)
    {
        _response = response;
        return;
    }
    
    [self completeOperation];
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    self.connection = nil;
    
    [self completeOperation];
}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    _error = error;
    
    self.connection = nil;
    
    [self completeOperation];
}

#pragma mark - NSSecureCoding

+ (BOOL)supportsSecureCoding
{
    return YES;
}

- (id)initWithCoder:(NSCoder *)decoder
{
    NSURLRequest *request = [decoder decodeObjectOfClass:NSURLRequest.class forKey:NSStringFromSelector(@selector(request))];
    
    self = [self initWithRequest:request];
    
    return self;
}

- (void)encodeWithCoder:(NSCoder *)coder
{
    [coder encodeObject:self.request forKey:NSStringFromSelector(@selector(request))];
}

#pragma mark - NSCopying

- (id)copyWithZone:(NSZone *)zone
{
    return [(ARURLOperation *)[self.class allocWithZone:zone] initWithRequest:self.request];;
}

@end