Pin pad constraints

- (void)updateConstraints {
    NSMutableArray *constraints = [NSMutableArray array];
    NSDictionary *views;
    NSDictionary *metrics = @{};
    
    void (^squareConstraint)(UIView *) = ^(UIView *aView) {
        [constraints addObject:[NSLayoutConstraint constraintWithItem:aView
                                                            attribute:NSLayoutAttributeHeight
                                                            relatedBy:NSLayoutRelationEqual
                                                               toItem:aView
                                                            attribute:NSLayoutAttributeWidth
                                                           multiplier:1.0
                                                             constant:0]];
    };
    
    //Iterate in threes
    for (NSUInteger idx=0; idx < self.subviews.count; idx++) {
        
        if (idx % 3 == 0 && idx >= 1 && idx <= 9) {
            views = @{
                      @"upperLeft": (idx > 3) ? self.subviews[idx-3] : [NSNull null],    //Get the left most view on the upper row
                      @"left":self.subviews[idx-2],
                      @"center":self.subviews[idx-1],
                      @"right":self.subviews[idx]
                      };
            
            [constraints addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-(>=1)-[left]-[center(==left)]-[right(==left)]-(>=1)-|"
                                                                                     options:NSLayoutFormatAlignAllCenterY|NSLayoutFormatAlignAllTop|NSLayoutFormatAlignAllBottom
                                                                                     metrics:metrics
                                                                                       views:views]];
            
            [constraints addObject:[NSLayoutConstraint constraintWithItem:views[@"center"]
                                                                attribute:NSLayoutAttributeCenterX
                                                                relatedBy:NSLayoutRelationEqual
                                                                   toItem:self
                                                                attribute:NSLayoutAttributeCenterX
                                                               multiplier:1.0
                                                                 constant:0.0]];
            
            if (views[@"upperLeft"] == [NSNull null]) {
                [constraints addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-[left]"
                                                                                         options:0
                                                                                         metrics:metrics
                                                                                           views:views]];
            } else {
                [constraints addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[upperLeft]-[left]"
                                                                                         options:0
                                                                                         metrics:metrics
                                                                                           views:views]];
            }
        }
        
        if (idx == self.subviews.count -1 ) {
            //Place the '0' and delete button
            [constraints addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"H:[zero]-[delete(==zero)]"
                                                                                     options:NSLayoutFormatAlignAllCenterY|NSLayoutFormatAlignAllTop|NSLayoutFormatAlignAllBottom
                                                                                     metrics:metrics
                                                                                       views:@{
                                                                                               @"zero":self.subviews.firstObject,
                                                                                               @"delete":self.subviews.lastObject
                                                                                               }]];
            
            [constraints addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[upperCenter]-[zero(==upperCenter)]-|"
                                                                                     options:NSLayoutFormatAlignAllCenterX
                                                                                     metrics:metrics
                                                                                       views:@{
                                                                                               @"zero":self.subviews.firstObject,
                                                                                               @"upperCenter":views[@"center"]
                                                                                               }]];
        }
        
        //Make them all square
        squareConstraint(self.subviews[idx]);

    }
    
    [self addConstraints:constraints];
    
    [super updateConstraints];    
}