LCKConcurrentOperation.h

//
//  LCKConcurrentOperation.h
//  LCKOperations
//
//  Created by Twig on 12/19/13.
//  Copyright (c) 2013 Lickability. All rights reserved.
//

@import Foundation;

@interface LCKConcurrentOperation : NSOperation

- (void)setExecuting:(BOOL)executing;
- (void)setFinished:(BOOL)finished;

/// Override to perform your concurrent work.
- (void)performConcurrentWork;

@end

LCKConcurrentOperation.m

//
//  LCKConcurrentOperation.m
//  LCKOperations
//
//  Created by Twig on 12/19/13.
//  Copyright (c) 2013 Lickability. All rights reserved.
//

#import "LCKConcurrentOperation.h"

@interface LCKConcurrentOperation ()

@property (nonatomic, getter = isExecuting) BOOL executing;
@property (nonatomic, getter = isFinished) BOOL finished;

@end

@implementation LCKConcurrentOperation

@synthesize executing = _executing;
@synthesize finished = _finished;

- (void)start {
    if ([self isCancelled]) {
        self.finished = YES;
        return;
    }
    
    [super start];
    self.executing = YES;
}

- (void)main {
    @try {
        [self performConcurrentWork];
    }
    @catch (NSException *exception) {
        NSAssert(!exception, nil);
    }
}

- (void)setFinished:(BOOL)finished {
    if (_finished == finished) {
        return;
    }
    
    NSString *isFinishedSelectorString = NSStringFromSelector(@selector(isFinished));
    
    [self willChangeValueForKey:isFinishedSelectorString];
    _finished = finished;
    [self didChangeValueForKey:isFinishedSelectorString];
    
    if (finished) {
        self.executing = NO;
    }
}

- (void)setExecuting:(BOOL)executing {
    if (_executing == executing) {
        return;
    }
    
    NSString *isExecutingSelectorString = NSStringFromSelector(@selector(isExecuting));
    
    [self willChangeValueForKey:isExecutingSelectorString];
    _executing = executing;
    [self didChangeValueForKey:isExecutingSelectorString];
}

- (BOOL)isConcurrent {
    return YES;
}

- (void)performConcurrentWork {
    NSAssert(NO, @"Subclasses must override %@", NSStringFromSelector(_cmd));
}

@end