Setting iOS constraints inside a subview

I'm new to constraints so I'm a little lost setting things up correctly. What I'm trying to do is have a mainview setup with constraints and inside of that view add a viewcontroller where I can then use that viewcontroller's view properties to constrain objects inside of that viewcontroller. I have setup a simple program to demonstrate what I'm trying to do.

viewcontroller.m

#import "ViewController.h"
#import "SearchBarViewController.h"

@interface ViewController (){
    UIView *mainView;
    UIView *topView;
    NSDictionary *viewsDictionary;
    NSDictionary *metrics;
    SearchBarViewController *sbvcSearchBarViewController;
}

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    //mainView---------------------------------------------------------------
    mainView = [[UIView alloc] init];
    [mainView setBackgroundColor:[UIColor grayColor]];
    mainView.translatesAutoresizingMaskIntoConstraints = NO;
    [self.view addSubview:mainView];
    //-------------------------------
    viewsDictionary = @{@"mainView": mainView};
    metrics = @{@"vSpacing":@20, @"hSpacing":@5};

    //topView----------------------------------------------------------------
    topView = [[UIView alloc] init];
    [topView setBackgroundColor:[UIColor darkGrayColor]];
    topView.translatesAutoresizingMaskIntoConstraints = NO;
    [mainView addSubview:topView];

    [self createMainConstraints];

    [self createSearchBar];
}

-(void)createMainConstraints{
    //Define the view Position and automatically the Size (for the mainView)
    NSArray *constraint_POS_V = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-vSpacing-[mainView]-vSpacing-|"
                                                                    options:0
                                                                    metrics:metrics
                                                                      views:viewsDictionary];

    NSArray *constraint_POS_H = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-hSpacing-[mainView]-hSpacing-|"
                                                                    options:0
                                                                    metrics:metrics
                                                                         views:viewsDictionary];
    [self.view addConstraints:constraint_POS_V];
    [self.view addConstraints:constraint_POS_H];

    //TopBarContainer Constraints ------------------------------------------------------
    [self.view addConstraint:[NSLayoutConstraint
                          constraintWithItem:topView
                          attribute:NSLayoutAttributeWidth
                          relatedBy:NSLayoutRelationEqual
                          toItem:mainView
                          attribute:NSLayoutAttributeWidth
                          multiplier:1
                          constant:0.0]];

    [self.view addConstraint:[NSLayoutConstraint
                          constraintWithItem:topView
                          attribute:NSLayoutAttributeHeight
                          relatedBy:NSLayoutRelationEqual
                          toItem:mainView
                          attribute:NSLayoutAttributeHeight
                          multiplier:.20
                          constant:0.0]];
    //xLoc / yLoc
    [self.view addConstraint:[NSLayoutConstraint
                          constraintWithItem:topView
                          attribute:NSLayoutAttributeCenterX
                          relatedBy:NSLayoutRelationEqual
                          toItem:mainView
                          attribute:NSLayoutAttributeCenterX
                          multiplier:1.0
                          constant:0.0]];

    [self.view addConstraint:[NSLayoutConstraint
                          constraintWithItem:topView
                          attribute:NSLayoutAttributeTop
                          relatedBy:NSLayoutRelationEqual
                          toItem:mainView
                          attribute:NSLayoutAttributeTop
                          multiplier:1.0
                          constant:0.0]];
}

-(void)createSearchBar{
    //SearchBarViewController-----------------------------------------------------------
    sbvcSearchBarViewController = [[SearchBarViewController alloc] init];
    sbvcSearchBarViewController.view.translatesAutoresizingMaskIntoConstraints = NO;
    [topView addSubview:sbvcSearchBarViewController.view];

    //sbvcSearchBarViewController Constraints --------------------------------------
    [self.view addConstraint:[NSLayoutConstraint
                          constraintWithItem:sbvcSearchBarViewController.view
                          attribute:NSLayoutAttributeWidth
                          relatedBy:NSLayoutRelationEqual
                          toItem:topView
                          attribute:NSLayoutAttributeWidth
                          multiplier:1
                          constant:0.0]];

    [self.view addConstraint:[NSLayoutConstraint
                          constraintWithItem:sbvcSearchBarViewController.view
                          attribute:NSLayoutAttributeHeight
                          relatedBy:NSLayoutRelationEqual
                          toItem:topView
                          attribute:NSLayoutAttributeHeight
                          multiplier:1
                          constant:0.0]];
    //xLoc / yLoc
    [self.view addConstraint:[NSLayoutConstraint
                          constraintWithItem:sbvcSearchBarViewController.view
                          attribute:NSLayoutAttributeCenterX
                          relatedBy:NSLayoutRelationEqual
                          toItem:topView
                          attribute:NSLayoutAttributeCenterX
                          multiplier:1.0
                          constant:0.0]];

    [self.view addConstraint:[NSLayoutConstraint
                          constraintWithItem:sbvcSearchBarViewController.view
                          attribute:NSLayoutAttributeCenterY
                          relatedBy:NSLayoutRelationEqual
                          toItem:topView
                          attribute:NSLayoutAttributeCenterY
                          multiplier:1.0
                          constant:0.0]];

}
- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

SearchBarViewController.m

#import "SearchBarViewController.h"

@interface SearchBarViewController (){
    UIView *searchBarSubView;
}

@end

@implementation SearchBarViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    [self.view setBackgroundColor:[UIColor purpleColor]];
    //
    searchBarSubView = [[UIView alloc] init];
    [searchBarSubView setBackgroundColor:[UIColor redColor]];
    [self.view addSubview:searchBarSubView];
    [self addConstraints];
}

- (void)addConstraints {
    [self.view addConstraint:[NSLayoutConstraint
                          constraintWithItem:searchBarSubView
                          attribute:NSLayoutAttributeWidth
                          relatedBy:NSLayoutRelationEqual
                          toItem:self.view
                          attribute:NSLayoutAttributeWidth
                          multiplier:1
                          constant:0.0]];

    [self.view addConstraint:[NSLayoutConstraint
                          constraintWithItem:searchBarSubView
                          attribute:NSLayoutAttributeHeight
                          relatedBy:NSLayoutRelationEqual
                          toItem:self.view
                          attribute:NSLayoutAttributeHeight
                          multiplier:1
                          constant:0.0]];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
}

@end

SearchBarViewController.m's view is constrained inside of viewcontroller and this works without errors. But when I try and use the constrained view's properties inside of SearchBarViewController.m to constrain the searchBarSubView I get this nasty compile error:

"Unable to simultaneously satisfy constraints. Probably at least one of the constraints in the following list is one you don't want. Try this: (1) look at each constraint and try to figure out which you don't expect; (2) find the code that added the unwanted constraint or constraints and fix it. (Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints) ( "", "", "", "", "", "", "" )

Will attempt to recover by breaking constraint "

I have seen this same error many times in the past few days working with constraints and I made it this far but now I'm at a loss. Please help!

Thanks!