Example of Objective-C UIViewController class.

SearchViewController.m

//
//  SearchViewController.m
//  
//
//  Created by Narikbi 
//  Copyright © 2016. All rights reserved.
//

#import "SearchViewController.h"
#import "VenueApi.h"
#import "VenueTableCell.h"
#import "PaginatorResponse.h"
#import "VenueViewController.h"
#import "LocationHelper.h"
#import "LoadingFooterView.h"
#import "CategoryGroupTableCell.h"
#import "SearchTableHeaderView.h"
#import "FilterViewController.h"
#import "FilterHelper.h"

#define kPageName @"Search page"
#define kPageId @(2)
#define kPerPage 20

@interface SearchViewController ()
@property (weak, nonatomic) IBOutlet UITableView *tableView;
@end

@implementation SearchViewController {
    UIRefreshControl *refreshControl;

    NSMutableArray *venues;
    UISearchBar *searchBar;
    NSInteger currentPage;
    PaginatorResponse *paginator;
    BOOL filterChanged;
    BOOL showHUD;
    NSString *prevSearch;
    FilterHelper *filter;
}

#pragma mark -
#pragma mark - Init

- (instancetype)init {
    self = [super init];
    if (self) {
        UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"Search" bundle:nil];
        self = [storyboard instantiateViewControllerWithIdentifier:NSStringFromClass([self class])];
    }
    return self;
}

- (void)initVars {
    venues = [NSMutableArray new];
    currentPage = 1;
    filterChanged = NO;
    showHUD = YES;
    prevSearch = @"";
    filter = [FilterHelper sharedInstance];
}

#pragma mark -
#pragma mark - Lifecycle

- (void)viewDidLoad {
    [super viewDidLoad];
    [self initVars];
    [self configUI];
    [self loadCategoryGroups];
    [self loadVenues];
    [self addObservers];    
}

- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
    [self configFilterButton];

    if (![searchBar.text isEqualToString:filter.searchText]) {
        filterChanged = YES;
        searchBar.text = filter.searchText;
    }

}

- (void)viewDidAppear:(BOOL)animated {
    [super viewDidDisappear:animated];
    
    // Start logging GoogleAnalytics
    [[GANRoutes sharedManager] startWithPage:kPageName];
    [AnalyticsKit pageId:kPageId];
    
    // If active tabbar controller
    if ([self isActiveVC]) {
        if (filterChanged) {
            searchBar.text = filter.searchText;
            currentPage = 1;
            [self loadVenues];
            filterChanged = NO;
        }
    }
    
}


- (void)addObservers {
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(searchFromNotification:) 
                                                 name:kNotificationSearchVenueWithText 
                                                 object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardWillShow:)
                                                 name:UIKeyboardWillShowNotification
                                               object:nil];
    
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardWillHide:)
                                                 name:UIKeyboardWillHideNotification
                                               object:nil];
    
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(filterApplied)
                                                 name:kNotificationFilterApplied
                                               object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(scrollToTop)
                                                 name:kNotificationSearchScrollToTop
                                               object:nil];

}

- (void)dealloc {
    [[NSNotificationCenter defaultCenter] removeObserver:self];
    [[GANRoutes sharedManager] removePage:kPageName];
}

#pragma mark -
#pragma mark - Actions

- (void)filterTapped {
    FilterViewController *vc = [FilterViewController new];
    UINavigationController *nc = [[UINavigationController alloc] initWithRootViewController:vc];
    [self presentViewController:nc animated:YES completion:nil];
    
    [[GANRoutes sharedManager] action:@"Click on filter button"];
    [AnalyticsKit pageId:kPageId actionId:@10];
}

- (void)filterApplied {
    currentPage = 1;
    __weak typeof(self) wself = self;
    if ([self isActiveVC]) {
        [wself loadVenues];
    } else {
        filterChanged = YES;
    }

    [[GANRoutes sharedManager] action:@"Filter applied"];
    [AnalyticsKit pageId:kPageId actionId:@11];
}

#pragma mark -
#pragma mark - Loading data

- (void)loadFirstPage {
    currentPage = 1;
    [self loadVenues];
}

- (void)loadVenues {
    
    paginator.loaded = NO;
    if (showHUD) {
        [SVProgressHUD show];
    } else {
        self.tableView.tableFooterView = [LoadingFooterView footerView];
    }
    
    // GAN
    if (searchBar.text.length) {
        [[GANRoutes sharedManager] action:@"Search by text" label:@"text" value:searchBar.text];
        filter.searchText = searchBar.text;
    }
    
    __weak typeof(self) wself = self;
    [VenueApi getVenuesWithText:searchBar.text cityId:nil sortType:SortTypeRating longitude:nil latitude:nil radius:nil filter:filter page:currentPage perPage:20 success:^(PaginatorResponse * response) {
        [SVProgressHUD dismiss];

        wself.tableView.tableFooterView = nil;
        [refreshControl endRefreshing];
        
        if (!paginator) {
            paginator = response;
            paginator.currentPage = 1;
            paginator.perPage = kPerPage;
            paginator.exactMatch = true;
        } else {
            paginator.perPage = response.perPage;
            paginator.totalPage = response.totalPage;
            paginator.totalItem = response.totalItem;
            paginator.exactMatch = response.exactMatch;
        }
        
        paginator.loaded = YES;
        if (currentPage == 1) {
            [venues removeAllObjects];
        }

        if (paginator.exactMatch) {
            [wself updateVenueCountLabel];
        } else {
            [wself showNoExactMatch];
        }
        
        [venues addObjectsFromArray:response.items];
        [wself.tableView reloadData];
        
    } failure:^(NSInteger code, NSString *message) {
        [SVProgressHUD dismiss];
        wself.tableView.tableFooterView = nil;
        [refreshControl endRefreshing];
    }];
    
}

#pragma mark -
#pragma mark - Search from notification

- (void)searchFromNotification:(NSNotification *)not {
    searchBar.text = not.userInfo[@"text"];
    currentPage = 1;
    showHUD = YES;
    [self loadVenues];
    
    [[GANRoutes sharedManager] action:@"Search by text" label:@"text" value:not.userInfo[@"text"]];
    [AnalyticsKit pageId:kPageId actionId:@12 value:searchBar.text];
}

#pragma mark -
#pragma mark - UITableView Datasource

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    return venues.count;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

    VenueTableCell *cell = [tableView dequeueReusableCellWithIdentifier:@"VenueTableCell"];
    [cell setVenue:venues[indexPath.row]];

    return cell;
}

#pragma mark -
#pragma mark - UITableView Delegate

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    [tableView deselectRowAtIndexPath:indexPath animated:YES];
    self.tableView.tableHeaderView = [SearchTableHeaderView viewWithCount:paginator.totalItem];
        
    Venue *v = venues[indexPath.row];
    VenueViewController *vc = [VenueViewController new];
    [vc setVenueCategoryId:v.venueCategoryId];
    [self.navigationController pushViewController:vc animated:YES];

    [[GANRoutes sharedManager] action:@"Детали заведения из списка" label:@"venue" value:v.analyticsKey];
    [AnalyticsKit pageId:kPageId actionId:@14 value:v.venueCategoryId.stringValue];
    
    if (searchBar.text.length) {
        if (![prevSearch isEqualToString:searchBar.text]) {
            prevSearch = searchBar.text;
            [AnalyticsKit pageId:kPageId actionId:@12 value:searchBar.text];
        }
        [AnalyticsKit pageId:kPageId actionId:@99 value:searchBar.text venueId:v.venueCategoryId];
    }

}

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
    return UITableViewAutomaticDimension;
}

- (void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath {
    NSInteger sections = [tableView numberOfSections];
    NSInteger items = [tableView numberOfRowsInSection:indexPath.section];
    
    if ([indexPath section] == sections - 1 && indexPath.item == items - 1) {
        // Last row
        if (paginator.loaded && paginator.hasNextPage) {
            currentPage++;
            paginator.currentPage = currentPage;
            self.tableView.tableFooterView = [LoadingFooterView footerView];
            showHUD = NO;
            [self loadVenues];
        }
    }
}

#pragma mark -
#pragma mark - Scroll notification

- (void)scrollToTopTable {
    __weak typeof(self) wself = self;
    
    [self performBlock:^{
        if ([self.tableView numberOfRowsInSection:0] > 0) {
            [wself.tableView scrollToRowAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:0] atScrollPosition:UITableViewScrollPositionTop animated:NO];
        }
    } afterDelay:.4];
}

#pragma mark -
#pragma mark - SearchBar Delegate

- (void)searchBarTextDidBeginEditing:(UISearchBar *)sb {
    searchBar.showsCancelButton = YES;    
}

- (void)searchBarCancelButtonClicked:(UISearchBar *)sb {
    [self.tableView reloadData];
    searchBar.showsCancelButton = NO;
    [searchBar resignFirstResponder];
    searchBar.text = @"";
    currentPage = 1;
    showHUD = YES;
    [self loadVenues];
}

- (void)searchBarSearchButtonClicked:(UISearchBar *)sb {
    [sb resignFirstResponder];
    showHUD = YES;
    currentPage = 1;
    [self loadVenues];
    [AnalyticsKit pageId:kPageId actionId:@12 value:searchBar.text];
}

#pragma mark -
#pragma mark - Keyboard Notifications

- (void)keyboardWillShow:(NSNotification *)notification {
    CGSize keyboardSize = [notification.userInfo[UIKeyboardFrameEndUserInfoKey] CGRectValue].size;
    NSNumber *rate = notification.userInfo[UIKeyboardAnimationDurationUserInfoKey];
    
    UIEdgeInsets contentInsets;
    if (UIInterfaceOrientationIsPortrait([[UIApplication sharedApplication] statusBarOrientation])) {
        contentInsets = UIEdgeInsetsMake(0.0, 0.0, (keyboardSize.height), 0.0);
    } else {
        contentInsets = UIEdgeInsetsMake(0.0, 0.0, (keyboardSize.width), 0.0);
    }
    __weak typeof(self) wself = self;
    [UIView animateWithDuration:rate.floatValue animations:^{
        wself.tableView.contentInset = contentInsets;
        wself.tableView.scrollIndicatorInsets = contentInsets;
    }];
}

- (void)keyboardWillHide:(NSNotification *)notification {
    NSNumber *rate = notification.userInfo[UIKeyboardAnimationDurationUserInfoKey];
    __weak typeof(self) wself = self;
    [UIView animateWithDuration:rate.floatValue animations:^{
        wself.tableView.contentInset = UIEdgeInsetsZero;
        wself.tableView.scrollIndicatorInsets = UIEdgeInsetsZero;
    }];
}

#pragma mark -
#pragma mark - ConfigUI

- (void)updateVenueCountLabel {
    self.tableView.tableHeaderView = [SearchTableHeaderView viewWithCount:paginator.totalItem];
}

- (void)showNoExactMatch {
    self.tableView.tableHeaderView = [SearchTableHeaderView viewWithText:@"Unfortunately, there are no places for your requests. 😕\nBut we recommend you to see:"];
}

- (void)scrollToTop {
    [self.tableView setContentOffset:CGPointZero animated:YES];
}

- (BOOL)isActiveVC {
    UINavigationController *nc = self.tabBarController.selectedViewController;
    return ([nc.viewControllers.lastObject isKindOfClass:[self class]]);
}

- (void)configFilterButton {
    if ([[FilterHelper sharedInstance] isEnabled]) {
        UIBarButtonItem *filterB = [[UIBarButtonItem alloc] initWithImage:[[UIImage imageNamed:@"icFilterActive"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal] style:UIBarButtonItemStylePlain target:self action:@selector(filterTapped)];
        self.navigationItem.rightBarButtonItem = filterB;
    } else {
        UIBarButtonItem *filterB = [[UIBarButtonItem alloc] initWithImage:[UIImage imageNamed:@"icFilterInactive"] style:UIBarButtonItemStylePlain target:self action:@selector(filterTapped)];
        self.navigationItem.rightBarButtonItem = filterB;
    }
    
}

- (void)configUI {
    [self.tableView registerNib:[UINib nibWithNibName:@"VenueTableCell" bundle:nil] forCellReuseIdentifier:@"VenueTableCell"];
    [self.tableView registerNib:[UINib nibWithNibName:@"CategoryGroupTableCell" bundle:nil] forCellReuseIdentifier:@"CategoryGroupTableCell"];
    
    searchBar = [UISearchBar new];
    searchBar.delegate = self;
    searchBar.placeholder = @"Search";
    self.navigationItem.titleView = searchBar;
    searchBar.tintColor = [UIColor whiteColor];
    
    self.tableView.estimatedRowHeight = 100;
    self.tableView.rowHeight = UITableViewAutomaticDimension;
    
    self.tableView.delegate = self;
    self.tableView.dataSource = self;
    
    self.tableView.tableFooterView = [UIView new];

    refreshControl = [[UIRefreshControl alloc] init];
    [refreshControl addTarget:self action:@selector(loadFirstPage) forControlEvents:UIControlEventValueChanged];
    [self.tableView addSubview:refreshControl];
    
}


@end