stackedAutoLayout.m

/**
 * This example programatically generates a series of UIViews each
 * 244x2000 and stacks them vertically inside of a scroll view.
 * To do this we dynamically build a dictionary as we generate
 * the views and simultaneously build an array of height 
 * constraints. Once the loop has completed we combine all of the
 * constraints into a single string and apply the last constraint
 * to the scrollview.
 *
 * This example assumes you're working in a UIViewController with
 * an IBOutlet for a UIScrollView. This also assumes the scrollView 
 * has been configured with NSLayoutConstraints in a UIStoryboard. 
 * The IBOutlet in this example is simply 'scrollView' referenced 
 * below as a property of self.
 *
 * Keep in mind that we apply the horizontal constraint to the scroll
 * view within the loop. This is becuase there is no horizontal 
 * relationship between the views in this example. If you were to stack
 * the views horizontally as opposed to vertically you would apply the
 * vertical constraint immediately within the loop and generate the
 * horizontal constraint to be applied last.
 */
- (void)viewDidLoad {
    [super viewDidLoad];
    
    self.scrollView.translatesAutoresizingMaskIntoConstraints = NO; // Necessary if using autolayout
    
    NSArray *colors = @[[UIColor redColor], [UIColor greenColor], [UIColor blueColor]];
    NSMutableDictionary *viewsDictionary = [NSMutableDictionary new];
    NSMutableArray *heightConstraints = [NSMutableArray new];
    int count = 1;
    
    for (UIColor *color in colors) {
        UIView *currentColor = [UIView new];
        currentColor.backgroundColor = color;
        [self.scrollView addSubview:currentColor];
        currentColor.translatesAutoresizingMaskIntoConstraints = NO; // Necessary if using autolayout
        
        NSString *viewKey = [NSString stringWithFormat:@"color%i", count];
        count += 1;
        [viewsDictionary setObject:currentColor forKey:viewKey];
        
        [heightConstraints addObject:[NSString stringWithFormat:@"[%@(2000)]",viewKey]];
        [self.scrollView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:[NSString stringWithFormat:@"H:|[%@(244)]|", viewKey]
                                                                                         options:0
                                                                                         metrics:0
                                                                                           views:viewsDictionary]];
    }
    
    // Generate and apply @"V:|[color1(2000)][color2(2000)][color3(2000)]|"
    NSString *verticalConstraints = [NSString stringWithFormat:@"V:|%@|", [heightConstraints componentsJoinedByString:@""]];
    [self.scrollView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:verticalConstraints
                                                                                     options:0
                                                                                     metrics:0
                                                                                       views:viewsDictionary]];
}