Auto Layout builds constraints in three ways. So far, you’ve read about two of them. First, you can lay out your constraints in Interface Builder (IB) and customize them to your needs. Second, you can build single constraints in code. The
NSLayoutConstraint class offers the
constraintWithItem: attribute:relatedBy:toItem:attribute:multiplier:constant: method, which enables you to create constraints one at a time, relating one item’s attribute to another. In this chapter, you’ll read about the third way: using a visual formatting language to express how items are laid out along vertical and horizontal axes.
This chapter explores what these visual constraints look like, how you build them, and how you use them in your projects. ...