Álvaro Ramírez

- (instancetype)initWithFrame:(CGRect)frame {
  self = [super initWithFrame:frame];
  if (self) {
    // Disable autoresizing mask translation for parent.
    self.translatesAutoresizingMaskIntoConstraints = NO;

    _subview1 = [[UIView alloc] init];
    // Disable autoresizing mask translation for subview.
    _subview1.translatesAutoresizingMaskIntoConstraints = NO;

    _subview1.backgroundColor = [UIColor redColor];
    [self addSubview:_subview1];

    // Creates a dictionary of bindings to be used in visual format.
    NSDictionary *viewBindings = NSDictionaryOfVariableBindings(_subview1);

    // H: horizontal layout
    // |-50- spacing in relation to superview
    // [_subview1(==50)] subview1's width
    [self addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-50-[_subview1(==50)]"
                                                                 options:0
                                                                 metrics:nil
                                                                   views:viewBindings]];
    [self addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[_subview1(==50)]"
                                                                 options:0
                                                                 metrics:nil
                                                                   views:viewBindings]];
  }
  return self;
}