Example of the use of even spacing constraints in a view controller (using the category from this answer: http://stackoverflow.com/questions/13075415/evenly-space-multiple-views-within-a-container-view/14568394#14568394)

gistfile1.m

- (void)viewDidLoad
{
    [super viewDidLoad];
    
    UILabel *label1 = [UILabel new];
    UILabel *label2 = [UILabel new];
    UILabel *label3 = [UILabel new];
    UILabel *label4 = [UILabel new];
    
    [label1 setTranslatesAutoresizingMaskIntoConstraints:NO];
    [label2 setTranslatesAutoresizingMaskIntoConstraints:NO];
    [label3 setTranslatesAutoresizingMaskIntoConstraints:NO];
    [label4 setTranslatesAutoresizingMaskIntoConstraints:NO];
    
    label1.text = @"Label 1";
    label2.text = @"Label 2";
    label3.text = @"Label 3";
    label4.text = @"Label 4";
    
    [self.view addSubview:label1];
    [self.view addSubview:label2];
    [self.view addSubview:label3];
    [self.view addSubview:label4];
    
    // Space the labels evenly along the vertical axis
    NSArray *constraints = [NSLayoutConstraint constraintsForEvenDistributionOfItems:@[label1, label2, label3, label4]
                                                              relativeToCenterOfItem:self.view
                                                                          vertically:YES];
    [self.view addConstraints:constraints];
    
    // Center each label horizontally
    [self.view addConstraint:[NSLayoutConstraint constraintWithItem:label1
                                                          attribute:NSLayoutAttributeCenterX
                                                          relatedBy:NSLayoutRelationEqual
                                                             toItem:self.view
                                                          attribute:NSLayoutAttributeCenterX
                                                         multiplier:1.0f
                                                           constant:0.0f]];
    
    [self.view addConstraint:[NSLayoutConstraint constraintWithItem:label2
                                                          attribute:NSLayoutAttributeCenterX
                                                          relatedBy:NSLayoutRelationEqual
                                                             toItem:self.view
                                                          attribute:NSLayoutAttributeCenterX
                                                         multiplier:1.0f
                                                           constant:0.0f]];
    
    [self.view addConstraint:[NSLayoutConstraint constraintWithItem:label3
                                                          attribute:NSLayoutAttributeCenterX
                                                          relatedBy:NSLayoutRelationEqual
                                                             toItem:self.view
                                                          attribute:NSLayoutAttributeCenterX
                                                         multiplier:1.0f
                                                           constant:0.0f]];
    
    [self.view addConstraint:[NSLayoutConstraint constraintWithItem:label4
                                                          attribute:NSLayoutAttributeCenterX
                                                          relatedBy:NSLayoutRelationEqual
                                                             toItem:self.view
                                                          attribute:NSLayoutAttributeCenterX
                                                         multiplier:1.0f
                                                           constant:0.0f]];
}