Задания для разработчика Яндекс.Музыки для iOS

NSString *wordsString = @"test, test hello! world test... hello";

NSCountedSet *wordsSet = [NSCountedSet set];
[wordsString enumerateSubstringsInRange:NSMakeRange(0, [wordsString length])
                                options:NSStringEnumerationByWords
                             usingBlock:^(NSString *substring, NSRange substringRange, NSRange enclosingRange, BOOL *stop) {
                                 [wordsSet addObject:substring];
                             }];

NSArray *uniqueWords = [wordsSet allObjects];
NSArray *sortedWords = [uniqueWords sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {
    NSUInteger count1 = [wordsSet countForObject:obj1];
    NSUInteger count2 = [wordsSet countForObject:obj2];
    
    return [@(count2) compare:@(count1)];
}];

NSArray *result = [sortedWords subarrayWithRange:NSMakeRange(0, MAX([sortedWords count], 3))];

#define after(DELAY, BLOCK) dispatch_after(dispatch_time(DISPATCH_TIME_NOW, \
                                           DELAY * NSEC_PER_SEC), \
                                           dispatch_get_main_queue(), BLOCK)

    NSOperationQueue *queue = [[NSOperationQueue alloc] init];
    NSBlockOperation *op = [[NSBlockOperation alloc] init];
    [op addExecutionBlock:^{
        for (int i = 0; i < 5; ++i) {
            if ([op isCancelled]) break; // <- strong
            NSLog(@"i = %d;", i);
        }
    }];
    [queue addOperation:op];
    [queue cancelAllOperations];
    
    __weak NSBlockOperation *weakOperation = op;
    after(0.5, ^{
        NSLog(@"Operation: %p", weakOperation);
    });
// Operation: 0x7527ae0

    NSOperationQueue *queue = [[NSOperationQueue alloc] init];
    NSBlockOperation *op = [[NSBlockOperation alloc] init];
    __weak NSBlockOperation *weakOperation = op;
    [op addExecutionBlock:^{
        for (int i = 0; i < 5; ++i) {
            if ([weakOperation isCancelled]) break; // <- weak
            NSLog(@"i = %d;", i);
        }
    }];
    [queue addOperation:op];
    [queue cancelAllOperations];
    
    after(0.5, ^{
        NSLog(@"Operation: %p", weakOperation);
    });
// Operation: 0x0

@implementation TTTestRetainCycle{
    NSOperationQueue *_queue; // <-
    NSArray *_data; // <-
}

-(void)dealloc{
    [_queue cancelAllOperations];
}

-(void)start{
    _queue = [[NSOperationQueue alloc] init];
    _data = @[@1, @2, @3, @4, @5];
    NSBlockOperation *op = [[NSBlockOperation alloc] init];
    __weak NSBlockOperation *weakOperation = op;
    [op addExecutionBlock:^{
        for (int i = 0; i < 5; ++i) {
            if ([weakOperation isCancelled]) break;
            NSLog(@"data[%d] = %d;", i, [_data[i] integerValue]); // <-
            sleep(1); // <-
        }
    }];
    [_queue addOperation:op];
}

@end

    __block TTTestRetainCycle *test = [TTTestRetainCycle new];
    [test start];
    after(1.5, ^{
        NSLog(@"Stopping");
        test = nil;
    });
// data[0] = 1;
// data[1] = 2;
// Stopping
// data[2] = 3;
// data[3] = 4;
// data[4] = 5;

-(void)start{
    // ...
    __typeof(self) __weak weakSelf = self;
    [op addExecutionBlock:^{
        for (int i = 0; i < 5; ++i) {
            if ([weakOperation isCancelled]) break;
            __typeof(self) strongSelf = weakSelf; // <-
            if (!strongSelf) break;  // <-
            NSLog(@"data[%d] = %d;", i, [strongSelf->_data[i] integerValue]); // <-
            sleep(1);
        }
    }];
    [_queue addOperation:op];
}
// data[0] = 1;
// data[1] = 2;
// Stopping

@implementation TTRetainer
+(void)retain:(id)object{
    [object retain];
}
+(void)autorelease:(id)object{
    [object autorelease];
}
@end

    // ...
    [op addExecutionBlock:^{
        for (int i = 0; i < 5; ++i) {
            if ([weakOperation isCancelled]) break;
            __typeof(self) strongSelf = weakSelf;
            if (!strongSelf) break;
            [TTRetainer retain:strongSelf]; // <-
            [TTRetainer autorelease:strongSelf]; // <-
            NSLog(@"data[%d] = %d;", 0, [strongSelf->_data[0] integerValue]);
            sleep(1);
        }
    }];
    // ...
// data[0] = 1;
// data[0] = 1;
// Stopping
// data[0] = 1;
// data[0] = 1;
// data[0] = 1;

    // ...
    [op addExecutionBlock:^{
        for (int i = 0; i < 5; ++i) {
            @autoreleasepool { // <-
                if ([weakOperation isCancelled]) break;
                __typeof(self) strongSelf = weakSelf;
                if (!strongSelf) break;
                [TTRetainer retain:strongSelf];
                [TTRetainer autorelease:strongSelf];
                NSLog(@"data[%d] = %d;", 0, [strongSelf->_data[0] integerValue]);
                sleep(1);
            }
        }
    }];
    // ...
// data[0] = 1;
// data[0] = 1;
// Stopping