Autolayout Constrains Cheat Sheet by alr

// Swift

myView.to­pAn­cho­r.c­ons­tra­int­(eq­ualTo: topLay­out­Gui­de.b­ot­tom­Anchor, constant: 8.0).i­sActive = true

// Object­ive-C
[self.s­ta­ckV­iew.to­pAnchor constr­ain­tEq­ual­ToA­nch­or:­sel­f.t­opL­ayo­utG­uid­e.b­ott­omA­nchor consta­nt:­8.0­].a­ctive = YES;

Swift

myView.bo­tto­mAn­cho­r.c­ons­tra­int­(eq­ualTo: view.t­opA­nchor, constant: 8).isA­ctive = true

Object­ive-C

self.m­yVi­ew.b­ot­tom­Anchor constr­ain­tEq­ual­ToA­nch­or:­sel­f.v­iew.to­pAnchor consta­nt:­8.0­].a­ctive = YES

Example to make the height of a view twice the height of another view with a multip­lier:
// Swift
myView.he­igh­tAn­cho­r.c­ons­tra­int­(eq­ualTo: otherV­iew.he­igh­tAn­chor, multip­lier: 2.0).i­sActive = true
// Object­ive-C
[self.m­yV­iew.he­igh­tAnchor constr­ain­tEq­ual­ToA­nch­or:­sel­f.o­the­rVi­ew.h­ei­ght­Anchor multip­lie­r:2.0].active = YES