constraints

@interface ViewController ()

@property (weak, nonatomic) IBOutlet UIScrollView *scrollViewForAccordian;
@property (weak, nonatomic) IBOutlet UIView* mainView;

@end

@implementation ViewController

@synthesize scrollViewForAccordian;
@synthesize mainView;

- (void)viewDidLoad {
    [super viewDidLoad];

    NSLayoutConstraint *widthConstraint = [NSLayoutConstraint constraintWithItem:self.mainView
                                                                       attribute:NSLayoutAttributeWidth
                                                                       relatedBy:NSLayoutRelationEqual
                                                                          toItem:scrollViewForAccordian
                                                                       attribute:NSLayoutAttributeWidth
                                                                      multiplier:1.0
                                                                        constant:0];

    NSLayoutConstraint *heightConstraint = [NSLayoutConstraint constraintWithItem:self.mainView
                                                                       attribute:NSLayoutAttributeHeight
                                                                       relatedBy:NSLayoutRelationEqual
                                                                          toItem:scrollViewForAccordian
                                                                       attribute:NSLayoutAttributeHeight
                                                                      multiplier:1.0
                                                                        constant:0];

    NSLayoutConstraint *rightConstraint = [NSLayoutConstraint constraintWithItem:self.mainView
                                                                       attribute:NSLayoutAttributeRight
                                                                       relatedBy:NSLayoutRelationEqual
                                                                          toItem:scrollViewForAccordian
                                                                       attribute:NSLayoutAttributeRight
                                                                      multiplier:1.0
                                                                        constant:0];

    NSLayoutConstraint *topConstraint = [NSLayoutConstraint constraintWithItem:self.mainView
                                                                       attribute:NSLayoutAttributeTop
                                                                       relatedBy:NSLayoutRelationEqual
                                                                          toItem:scrollViewForAccordian
                                                                       attribute:NSLayoutAttributeTop
                                                                      multiplier:1.0
                                                                        constant:0];


    [mainView addConstraints:@[widthConstraint, heightConstraint, topConstraint, rightConstraint]];