How to determine if NSLayoutConstraint is horizontal or vertical?

Question

It seems like it should be a simple task, but is there a way to say programmatically if it NSLayoutConstraintis a horizontal or vertical constraint?

The only way I can try to do this is to call [constraint description];and then search in the resulting string for "V:"or"H:"

I want to find this information: I have two almost identical restrictions set on prototype UITableViewCellmy own storyboard, the only difference is that we describe the horizontal distance from superviewand the other vertical. I want to remove vertical, programmatically add constraints to describe adding a new view, given that a specific parameter is being returned from my server.

Any suggestions would be extremely helpful!

EDIT:

I accepted greymouser's answer because its explanation is a fantastic answer, and I did work on parsing the description, but I also want to give credit to @kongtomorrow, who also suggested this answer via twitter before greymouser answered me here! Thanks for the help!

Here is the actual code that I used to find the constraint:

NSArray *constraints = [bubble constraints];

for (NSLayoutConstraint *constraint in constraints) {
    if ([[constraint firstItem] isEqual:messageLabel] && [[constraint secondItem] isEqual:bubble] && [constraint secondAttribute] == NSLayoutAttributeTop) {
        [bubble removeConstraint:constraint];
    }
}

firstItem, secondItem, secondAttribute , , , !

Answer 1

. VFL NSLayoutConstraint +:constraintWithItem:attribute:relatedBy:toItem:attribute:multiplier:constant:.

, firstAttribute secondAttribute NSLayoutAttribute , , . VFL, , , , . , firstAttribute , NSLayoutAttributeLeft, - NSLayoutAttributeLeft , , , . .

, , NSLayoutConstraint, /, mainting , H V.

Answer 2

, , , . : NSLayoutAttributeLeading NSLayoutAttributeTrailing, NSLayoutAttributeTop NSLayoutAttributeBottom.

, IB, .