This is an example UIViewController of how I like to build the views using auto layout by code.

FJBViewControllerAutolayoutExample.m

// -- Import ConstraintPack, by Erica https://github.com/erica/Auto-Layout-Demystified great book to learn about auto layout.
// In the Pack, I've added more cases I've been needing to build the UI

// Example in the constraick pack:
// #define CONSTRAINT_ALIGNING_PAIR_LEFT(VIEW1, VIEW2, INDENT) [NSLayoutConstraint constraintWithItem: VIEW2 attribute: NSLayoutAttributeLeft relatedBy: NSLayoutRelationEqual toItem:VIEW1 attribute: NSLayoutAttributeLeft multiplier: 1.0f constant: INDENT]

#import "ConstraintPack.h"

@interface FJBViewController ()
// -- In the NSMutableArray is where I save all the constraints I want to add.
@property (nonatomic, strong) NSMutableArray *autolayoutConstraints;

// -- Views
@property (nonatomic, strong) UIImageView *firstImageView;  // -- Examples of Views...
@property (nonatomic, strong) UIImageView *secondImageView;
@property (nonatomic, strong) UILabel *introductionLabel;
@end

...

- (void)viewDidLoad
{
    [super viewDidLoad];
    
    _autolayoutConstraints = [[NSMutableArray alloc] init];
    
    [self.view addSubview:self.firstImageView];
    [self.view addSubview:self.secondImageView];
    [self.view addSubview:self.descriptionLabel];
    
    // -- After subviews added, I add the constraints.
    
    InstallConstraints(self.autolayoutConstraints, LayoutPriorityRequired, NSStringFromClass([self class]));
}


#pragma mark - Properties

- (UIImageView *)firstImageView
{
    if (_firstImageView) {
        return _firstImageView;
    }
    
    _firstImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"..."]];
    
    //-- In this part I define all the properties of the view
    
    PREPCONSTRAINTS(_firstImageView); // -- Now I start adding the constraints.
    
    //-- I want to center the imageView in the self.view horizontal axis
    [self.autolayoutConstraints addObject:CONSTRAINT_CENTERING_PAIR_H(self.view, _firstImageView)]; //x
    //-- With this constraint I want to align at the bottom self.view and _firstImageView
    [self.autolayoutConstraints addObject:CONSTRAINT_ALIGNING_PAIR_BOTTOM(self.view, _firstImageView, 0)]; //y
    
    //-- Here I've added the constraints always in the same order when you define a frame, x,y,width and height.
    // In this case I don't need to add the width or height because I want to use the intrinsic content size
    
    return _firstImageView;
}

- (UILabel *)introductionLabel
{
    if (_introductionLabel) {
        return _introductionLabel;
    }
    
    _introductionLabel = [[UILabel alloc] initWithFrame:CGRectZero];
    _introductionLabel.numberOfLines = 2;
    _introductionLabel.backgroundColor = self.view.backgroundColor;
    _introductionLabel.textAlignment = NSTextAlignmentCenter;
    _introductionLabel.text = NSLocalizedString(@"ViewControllerIntroductionLabelTitle", @"ViewControllerIntroductionLabelTitle");
    [_introductionLabel setContentMode:UIViewContentModeCenter];
    
    PREPCONSTRAINTS(_introductionLabel);
    
    //-- Align to the left self.view + 20px
    [self.autolayoutConstraints addObject:CONSTRAINT_ALIGNING_PAIR_LEFT(self.view, _introductionLabel, 20)]; //x
    // -- In the next constraints I want to have the introductionLabel 32px underneath secondImageView.
    [self.autolayoutConstraints addObject:CONSTRAINT_STACKING_V(self.secondImageView, _introductionLabel, 32)]; //y
    [self.autolayoutConstraints addObject:CONSTRAINT_ALIGNING_PAIR_RIGHT(self.view, _introductionLabel, 20)]; //width
    
    return _introductionLabel;
}