Using protocols for detecting value changes in UISegmentedControl

Question

I have a UISegmentedControl in a UITableViewCell, that I need to listen for value changes in the TableViewController.

So far I know I have to use protocols to be able to do this, but I'm not sure where to put the code. Should it be in the UITableViewCell? In the ViewController? This is all a bit confusing for me.

I need some pinpointing on where to start, or even better, some code example?

Answer 1

From what we talked in comments, you want to reload UITableView every time the user changes UISegmentedControl selection.

First you need to add this to your UISegmentedControl:

self.segmentedControl.addTarget(self, action: "segmentedControlIndexChanged", forControlEvents: .ValueChanged)

But do this just after UISegmentedControl initiation, and not in cellForRow like in the second answer, because it would be called on every cell reuse (which will be a lot if you have more cells than can appear on the screen).

Then you do you logic in this method:

func segmentedControlIndexChanged() {
    // change your UITableView data or even swap your UITableViews (if you have 2)
}

Please remember, that when you change the index manually, you need to call event change manually as well:

segmentedControl.sendActionsForControlEvents(.ValueChanged)

Answer 2

You can add method in your tableViewController.

In cellForRow Method of UITableViewController add below code.

[cell.yourSegmentControl addTarget:self action:@selector(handleSegmentControlEvent:) forControlEvents: UIControlEventValueChanged];

Then implement method in same controller,

- (void)handleSegmentControlEvent:(id)sender{
}

Hope it helps.

Answer 3

Here is the code using protocol.In this sample , you can observe the value change of the segmentControl. You can know which cell's segment being tapped and know the segment data change.

// ViewController.m

#import "ViewController.h"
#import "segmentTestCell.h"

@interface ViewController ()<UITableViewDataSource, UITableViewDelegate, segmentTestCellDelegate>

@property (nonatomic, strong) UITableView *table;

@end

@implementation ViewController
#pragma mark - LifeCycle
- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    [self.table registerClass:[segmentTestCell class] forCellReuseIdentifier:@"cellId"];
    [self.view addSubview:self.table];
}

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

#pragma mark - UITableViewDataSource, UITabBarDelegate
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    return 100;
}

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    return 1;
}

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
    return 50;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    segmentTestCell *cell = [tableView dequeueReusableCellWithIdentifier:@"cellId"];
    cell.indexPath = indexPath;
    if (!cell.delegate) {
        cell.delegate = self;
    }
    return cell;
}

#pragma mark - segmentTestCellDelegate
- (void)segmentChangeAtIndexPath:(NSIndexPath *)indexPath SelectIndex:(NSInteger)selectedIndex SelectTitle:(NSString *)selectedTitle {
    NSLog(@"%lu - %lu - %@",indexPath.section,indexPath.row,selectedTitle);

    // do something by yourself
}

#pragma mark - Getter
- (UITableView *)table {
    if (!_table) {
        _table = [[UITableView alloc]initWithFrame:self.view.bounds style:UITableViewStylePlain];
        _table.allowsSelection = NO;
        _table.dataSource = self;
        _table.delegate = self;
    }
    return _table;
}

@end

// segmentTestCell.h

#import <UIKit/UIKit.h>

@protocol segmentTestCellDelegate <NSObject>
@optional
- (void)segmentChangeAtIndexPath: (NSIndexPath *)indexPath SelectIndex: (NSInteger)selectedIndex SelectTitle: (NSString *)selectedTitle;
@end

@interface segmentTestCell : UITableViewCell

@property (nonatomic, strong) UISegmentedControl *segmentControl;

@property (nonatomic, strong) NSIndexPath *indexPath;
@property (nonatomic, weak) id<segmentTestCellDelegate> delegate;

@end

// segmentTestCell.m

#import "segmentTestCell.h"

#define titles @[@"A",@"B",@"C"]

@interface segmentTestCell()

@end

@implementation segmentTestCell

- (void)awakeFromNib {
    [super awakeFromNib];
    // Initialization code
}

- (void)setSelected:(BOOL)selected animated:(BOOL)animated {
    [super setSelected:selected animated:animated];

    // Configure the view for the selected state
}

- (instancetype)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier {
    self = [super initWithStyle:style reuseIdentifier:reuseIdentifier];
    if (self) {
        self.segmentControl.frame = CGRectMake(20, 10, 100, 30);
        [self.contentView addSubview:self.segmentControl];
    }
    return self;
}

- (void)segmentValueChange: (id)sender {
    // do something
    UISegmentedControl *control = (UISegmentedControl *)sender;
    if ([self.delegate respondsToSelector:@selector(segmentChangeAtIndexPath:SelectIndex:SelectTitle:)]) {
        [self.delegate segmentChangeAtIndexPath:_indexPath SelectIndex:control.selectedSegmentIndex SelectTitle:titles[control.selectedSegmentIndex]];
    }
}

- (UISegmentedControl *)segmentControl {
    if (!_segmentControl) {
        _segmentControl = [[UISegmentedControl alloc]initWithItems:titles];
        [_segmentControl addTarget:self action:@selector(segmentValueChange:) forControlEvents:UIControlEventValueChanged];
    }
    return _segmentControl;
}

@end