Picker view example

#import <UIKit/UIKit.h>

@interface PickerViewController : UIViewController <UIPickerViewDelegate, UIPickerViewDataSource>

@end

@interface PickerViewController ()

{
    NSArray *letterArray;
}

@property (strong, nonatomic) UIView *viewForMainPicker;

@end

@implementation PickerViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.tabBarController.tabBar.hidden = YES;
    //[self.view setBackgroundColor:[UIColor clearColor]];
    [self.view setBackgroundColor:[UIColor systemYellowColor]];

    letterArray = @[@"",@"A",@"B",@"C",@"D"];

    UIBarButtonItem *pBtn = [[UIBarButtonItem alloc] initWithTitle:@"picker"
                                                             style:UIBarButtonItemStylePlain
                                                            target:self
                                                            action:@selector(launchPicker:)];
    self.navigationItem.rightBarButtonItem = pBtn;
}

- (void)launchPicker:(id)sender {

    // let's use auto-layout / constraints instead of explicit frames
    //self.viewForMainPicker = [[UIView alloc]initWithFrame:CGRectMake(0, 400, [[UIScreen mainScreen] bounds].size.width, 220)];
    //UIToolbar *toolBar = [[UIToolbar alloc]initWithFrame:CGRectMake(0, 0, [[UIScreen mainScreen] bounds].size.width, 44)];
    //UIPickerView *mainPicker = [[UIPickerView alloc] initWithFrame:CGRectMake(0, 0, [[UIScreen mainScreen] bounds].size.width, 220)];

    self.viewForMainPicker = [UIView new];
    UIToolbar *toolBar = [UIToolbar new];
    UIPickerView *mainPicker = [UIPickerView new];

    UIFont *arrowfont = [UIFont boldSystemFontOfSize:40];
    UIFont *titlefont = [UIFont boldSystemFontOfSize:28];
    UIBarButtonItem *doneBtn = [[UIBarButtonItem alloc] initWithTitle:@"→"
                                                                style:UIBarButtonItemStylePlain
                                                               target:self
                                                               action:@selector(fakeEvent)];
    UIBarButtonItem *title = [[UIBarButtonItem alloc] initWithTitle:@"Select Gender"
                                                              style:UIBarButtonItemStylePlain
                                                             target:nil
                                                             action:nil];
    UIBarButtonItem *flex = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace
                                                                          target:self
                                                                          action:nil];
    [doneBtn setTitleTextAttributes:[NSDictionary dictionaryWithObjectsAndKeys:
                                     [UIColor colorWithRed:0.933 green:0.122 blue:0.145 alpha:1.00], NSForegroundColorAttributeName,
                                     arrowfont, NSFontAttributeName, nil] forState:UIControlStateNormal];
    [title setTitleTextAttributes:[NSDictionary dictionaryWithObjectsAndKeys:
                                   [UIColor colorWithRed:0.933 green:0.122 blue:0.145 alpha:1.00], NSForegroundColorAttributeName,
                                   titlefont, NSFontAttributeName, nil] forState:UIControlStateNormal];
    NSArray *btnArray = [[NSArray alloc] initWithObjects:flex,flex,title,flex,doneBtn,nil];

    mainPicker.delegate = self;
    mainPicker.dataSource = self;

    [toolBar setItems:btnArray];
    [_viewForMainPicker addSubview:mainPicker];
    [_viewForMainPicker addSubview:toolBar];

    [self.view addSubview:_viewForMainPicker];

    _viewForMainPicker.translatesAutoresizingMaskIntoConstraints = NO;
    mainPicker.translatesAutoresizingMaskIntoConstraints = NO;
    toolBar.translatesAutoresizingMaskIntoConstraints = NO;

    UILayoutGuide *g = self.view.safeAreaLayoutGuide;

    [NSLayoutConstraint activateConstraints:@[

        [_viewForMainPicker.topAnchor constraintEqualToAnchor:g.topAnchor constant:400.0],
        [_viewForMainPicker.leadingAnchor constraintEqualToAnchor:g.leadingAnchor constant:0.0],
        [_viewForMainPicker.trailingAnchor constraintEqualToAnchor:g.trailingAnchor constant:0.0],
        [_viewForMainPicker.heightAnchor constraintEqualToConstant:220.0],

        [toolBar.topAnchor constraintEqualToAnchor:_viewForMainPicker.topAnchor constant:0.0],
        [toolBar.leadingAnchor constraintEqualToAnchor:_viewForMainPicker.leadingAnchor constant:0.0],
        [toolBar.trailingAnchor constraintEqualToAnchor:_viewForMainPicker.trailingAnchor constant:0.0],
        [toolBar.heightAnchor constraintEqualToConstant:44.0],

        [mainPicker.topAnchor constraintEqualToAnchor:toolBar.bottomAnchor constant:0.0],
        [mainPicker.leadingAnchor constraintEqualToAnchor:_viewForMainPicker.leadingAnchor constant:0.0],
        [mainPicker.trailingAnchor constraintEqualToAnchor:_viewForMainPicker.trailingAnchor constant:0.0],
        [mainPicker.bottomAnchor constraintEqualToAnchor:_viewForMainPicker.bottomAnchor constant:0.0],

    ]];

    self.viewForMainPicker.backgroundColor = [UIColor whiteColor];

}

- (void)fakeEvent {
    NSLog(@"selected");
}

- (NSInteger)numberOfComponentsInPickerView:(nonnull UIPickerView *)pickerView {
    return 1;
}

- (NSInteger)pickerView:(nonnull UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {
    return letterArray.count;
}

- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component {
    return letterArray[row];
}

- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component {
    NSString *newString = [NSString stringWithFormat:@"%@", letterArray[row]];
    NSLog(@"passing: %@",newString);
}

@end