ReactiveCocoa takeUntil 2 possible signals?

问题:

So I have successfully turned a button into an off and on switch that changes the label.

I was also able to have it start a timed processed set off when that is to occur, and it have the ability to shut off the timed process.

Anyways I need to way to shut down the timed process I was wondering if there was a way to stop it without using the disposable. With a second takeUntil signal.

Edit I think what I was trying to do was slightly misleading let me show my current solution that works.

-(RACSignal*) startTimer {
    return [[RACSignal interval:1.0
            onScheduler:[RACScheduler mainThreadScheduler]]
             startWith:[NSDate date]];
}

-(void) viewWillAppear:(BOOL)animated {}

-(void) viewDidLoad {

    self.tableView.delegate = self;
    self.tableView.dataSource = self;

    RACSignal* pressedStart = [self.start rac_signalForControlEvents:UIControlEventTouchUpInside];

    @weakify(self);
    RACSignal* textChangeSignal = [pressedStart map:^id(id value) {
        @strongify(self);
        return [self.start.titleLabel.text isEqualToString:@"Start"] ? @"Stop" : @"Start";
    }];

    // Changes the title
    [textChangeSignal subscribeNext:^(NSString* text) {
        @strongify(self);
        [self.start setTitle:text forState:UIControlStateNormal];
    }];

    RACSignal* switchSignal = [[textChangeSignal map:^id(NSString* string) {
        return [string isEqualToString:@"Stop"] ? @0 : @1;

    }] filter:^BOOL(id value) {
        NSLog(@"Switch %@",value);
        return [value boolValue];
    }];


    [[self rac_signalForSelector:@selector(viewWillAppear:)]
     subscribeNext:^(id x) {


    }];

    static NSInteger t = 0;
    // Remake's it self once it is on finished.
    self.disposable = [[[textChangeSignal filter:^BOOL(NSString* text) {
        return [text isEqualToString:@"Stop"] ? [@1 boolValue] : [@0 boolValue];
    }]
                                  flattenMap:^RACStream *(id value) {
                                      NSLog(@"Made new Sheduler");
                                      @strongify(self);
                                      return [[self startTimer] takeUntil:switchSignal];
                                  }] subscribeNext:^(id x) {
                                      NSLog(@"%@",x);
                                      @strongify(self);
                                      t = t + 1;
                                      NSLog(@"%zd",t);

                                      [self updateTable];
                                  }];

    [[self rac_signalForSelector:@selector(viewWillDisappear:)] subscribeNext:^(id x) {
        NSLog(@"viewWillAppear Dispose");
        [self.disposable dispose];
    }];

}


-(BOOL) isGroupedExcercisesLeft {
    BOOL isGroupedLeft = NO;
    for (int i =0;i < [self.excercises count]; i++) {
        Excercise* ex = [self.excercises objectAtIndex:i];
        if(ex.complete == NO && ex.grouped == YES) {
            isGroupedLeft = YES;
            break;
        }
    }
    return isGroupedLeft;
}

-(void) updateTable {

    // Find the
    NSInteger nextRow;

    if (([self.excercises count] > 0 || self.excercises !=nil) && [self isGroupedExcercisesLeft]) {

        for (int i =0;i < [self.excercises count]; i++) {

            Excercise* ex = [self.excercises objectAtIndex:i];
            if(ex.complete == NO && ex.grouped == YES) {
                nextRow = i;
                break;
            }

        }

        NSIndexPath* path = [NSIndexPath indexPathForItem:nextRow inSection:0];
        NSArray* indexPath = @[path];
        // update //

        Excercise* ex = [self.excercises objectAtIndex:nextRow];
        [self.tableView scrollToRowAtIndexPath:path atScrollPosition:UITableViewScrollPositionTop animated:YES];
        if (ex.seconds <= 0) {
            RLMRealm* db = [RLMRealm defaultRealm];
            [db beginWriteTransaction];
            ex.complete = YES;
            [db commitWriteTransaction];
        }
        else {
            // Update Seconds
            RLMRealm* db = [RLMRealm defaultRealm];
            [db beginWriteTransaction];
            ex.seconds = ex.seconds - 1000;
            NSLog(@"Seconds: %zd",ex.seconds);
            [db commitWriteTransaction];
            // Update table
            [self.tableView reloadRowsAtIndexPaths:indexPath withRowAnimation:UITableViewRowAnimationNone];
        }


    } else {
        NSLog(@"Done");

        SIAlertView *alertView = [[SIAlertView alloc] initWithTitle:@"Deskercise" andMessage:@"Excercises Complete"];
        [alertView addButtonWithTitle:@"Ok"
                                 type:SIAlertViewButtonTypeDefault
                              handler:^(SIAlertView *alert) {

                              }];

        alertView.transitionStyle = SIAlertViewTransitionStyleBounce;
        [alertView show];
        NSLog(@"Dispose");
        [self.disposable dispose];

    }

}

回答1:

The issue with using takeUntil:self.completeSignal is that when you change completeSignal to another value, it isn't passed to any function that was already waiting for the variable that completeSignal was previously holding.

- (RACSignal*) startTimer {
    @weakify(self)
    return [[[RACSignal interval:1.0
                 onScheduler:[RACScheduler mainThreadScheduler]]
         startWith:[NSDate date]]
        takeUntil:[[self.start rac_signalForControlEvents:UIControlEventTouchUpInside]
                   merge:[[RACObserve(self, completeSignal) skip:1] flattenMap:
                          ^RACStream *(RACSignal * signal) {
                              @strongify(self)
                              return self.completeSignal;
                          }]]
        ];
}

The signal is now observing and flattening completeSignal, which will give the desired effect. Signals that complete without sending next events are ignored by takeUntil:, so use self.completedSignal = [RACSignal return:nil], which sends a single next event and then completes.

However, this code is anything but ideal, let's look at a better solution.

@property (nonatomic, readwrite) RACSubject * completeSignal;

- (RACSignal*) startTimer {
    return [[[RACSignal interval:1.0
                 onScheduler:[RACScheduler mainThreadScheduler]]
         startWith:[NSDate date]]
        takeUntil:[[self.start rac_signalForControlEvents:UIControlEventTouchUpInside]
                   merge:self.completeSignal]
        ];
}
- (void) viewDidLoad {
    [super viewDidLoad];
    self.completeSignal = [RACSubject subject];
    self.tableView.delegate = self;
    self.tableView.dataSource = self;

    RACSignal * pressedStart = [self.start rac_signalForControlEvents:UIControlEventTouchUpInside];

    @weakify(self);
    RACSignal* textChangeSignal = [[pressedStart startWith:nil] scanWithStart:@"Stop" reduce:^id(id running, id next) {
        return @{@"Start":@"Stop", @"Stop":@"Start"}[running];
    }];

    [self.start
     rac_liftSelector:@selector(setTitle:forState:)
     withSignals:textChangeSignal, [RACSignal return:@(UIControlStateNormal)], nil];

    [[[pressedStart flattenMap:^RACStream *(id value) { //Using take:1 so that it doesn't get into a feedback loop
        @strongify(self);
        return [self startTimer];
    }] scanWithStart:@0 reduce:^id(NSNumber * running, NSNumber * next) {
        return @(running.unsignedIntegerValue + 1);
    }] subscribeNext:^(id x) {
        @strongify(self);
        [self updateTable];
        NSLog(@"%@", x);
    }];
}

- (void) updateTable {
    //If you uncomment these then it'll cause a feedback loop for the signal that calls updateTable

    //[self.start sendActionsForControlEvents:UIControlEventTouchUpInside];
    //[self.completeSignal sendNext:nil];
    if ([self.excercises count] > 0 || self.excercises !=nil) {
    } else {
    }
}

Let's run through the list of changes:

• completeSignal is now a RACSubject (a manually controlled RACSignal).
• For purity and to get rid of the @weakify directive, textChangeSignal now uses the handy scanWithStart:reduce: method, which lets you access an accumulator (this works well for methods that work with an incrementing or decrementing number).
• start's text is now being changed by the rac_liftSelector function, which takes RACSignals and unwraps them when all have fired.
• Your flattenMap: to replace pressedStart with [self startTimer] now uses scanWithStart:reduce, which is a much more functional way to keep count.

I'm not sure if you were testing by having updateTable contain completion signals but it definitely causes a logic issue with your flattenMap: of pressedButton, the resulting feedback loop eventually crashes the program when the stack overflows.