Auto Layout equal spacing with a little math

gistfile1.m

NSMutableArray *horizontalConstraints = [NSMutableArray array];
// Fixed width, same width for all buttons (33)
[horizontalConstraints addObject:[NSLayoutConstraint constraintWithItem:left attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.f constant:33.f]];
[horizontalConstraints addObject:[NSLayoutConstraint constraintWithItem:left attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:center1 attribute:NSLayoutAttributeWidth multiplier:1.f constant:0]];
[horizontalConstraints addObject:[NSLayoutConstraint constraintWithItem:left attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:center2 attribute:NSLayoutAttributeWidth multiplier:1.f constant:0]];
[horizontalConstraints addObject:[NSLayoutConstraint constraintWithItem:left attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:right attribute:NSLayoutAttributeWidth multiplier:1.f constant:0]];

// Align baselines
[horizontalConstraints addObject:[NSLayoutConstraint constraintWithItem:left attribute:NSLayoutAttributeBaseline relatedBy:NSLayoutRelationEqual toItem:center1 attribute:NSLayoutAttributeBaseline multiplier:1.f constant:0]];
[horizontalConstraints addObject:[NSLayoutConstraint constraintWithItem:left attribute:NSLayoutAttributeBaseline relatedBy:NSLayoutRelationEqual toItem:center2 attribute:NSLayoutAttributeBaseline multiplier:1.f constant:0]];
[horizontalConstraints addObject:[NSLayoutConstraint constraintWithItem:left attribute:NSLayoutAttributeBaseline relatedBy:NSLayoutRelationEqual toItem:right attribute:NSLayoutAttributeBaseline multiplier:1.f constant:0]];

// Use 2 * superview.centerX to calculate width.
// Then position views at 0, 1/3, 2/3 and 1.
// Nudge the views a little with some margin and half-widths.
[horizontalConstraints addObject:[NSLayoutConstraint constraintWithItem:left attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterX multiplier:2.f*0.f constant:33.f/2.f + 8.f]];
[horizontalConstraints addObject:[NSLayoutConstraint constraintWithItem:center1 attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterX multiplier:2.f*1.f/3.f constant:8.f]];
[horizontalConstraints addObject:[NSLayoutConstraint constraintWithItem:center2 attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterX multiplier:2.f*2.f/3.f constant:-8.f]];
[horizontalConstraints addObject:[NSLayoutConstraint constraintWithItem:right attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterX multiplier:2.f*1.f constant:-33.f/2.f - 8.f]];

// Yes, you have to do some calculations, but they are pretty easy.
// I get 57px, 58px, 57px in portrait and 111px, 111px and 110px in landscape.