update UITableViewCell from other method - ios

Question

i have search thousand in GG to find solution update data to UITableViewCell but all show me the solution is
UITableViewCell *cell=(UITableViewCell*)[self.tableView cellForRowAtIndexPath:indexPath];
but the cell is nil for all cells that are visible. I have use NSNotification to send data from one method to ViewController.m , and the Reiever method i want update data to cell by indexPath. but all cell is nil and cannt not update that.
here my code
ViewController.h
#import <UIKit/UIKit.h>
#interface ViewController : UIViewController <UITableViewDelegate, UITableViewDataSource>
#property(nonatomic, strong) IBOutlet UITableView *tableView;
#end
ViewController.m
#implementation ViewController
{
}
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
[[NSNotificationCenter defaultCenter]addObserver:self selector:#selector(theReciever:) name:#"theSender" object:nil];
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return [recipes count];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *simpleTableIdentifier = #"SimpleTableCell";
UITableViewCell* cell = [self.tableView dequeueReusableCellWithIdentifier:simpleTableIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:simpleTableIdentifier];
NSLog(#"cell nil");
}
NSString *idgame=#"Gamexyz";
cell.textLabel.text = idgame;
cell.tag=indexPath.row;
return cell;
}
-(void)theReciever:(NSNotification*)notif{
if([notif.object isKindOfClass:[packeData class]]){
packeData *data=[notif object];
NSString *key=data.key;
NSInteger *index=[key integerValue];
NSIndexPath *indexPath=[NSIndexPath indexPathWithIndex:index];
UITableViewCell *cell=(UITableViewCell*)[self.tableView cellForRowAtIndexPath:indexPath];
//UITableViewCell *cell=(UITableViewCell*)[self.tableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:7 inSection:0]];
if(cell==nil)
{
NSLog(#"cell NULL");
}else{
cell.textLabel.text=data.process;
}
}else{
NSLog(#"ERR: object not recognised");
}
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
#end
any one can help me or solution example for update data in UITableViewCell by indexPath

Answer 1

NOTE: below is just an example u can do it in new project
One thing u need to change the data model packeData, lets say it contains key as NSIntager which holdes the index of the cell and process is NSString which holds the progress as string value for example
in packeData.h
#import <Foundation/Foundation.h>
#interface packeData : NSObject
#property (nonatomic, assign) NSInteger key; //holds index
#property (nonatomic, strong) NSString *process; //holds the progress info
#end
and in packeData.m
#import "packeData.h"
#implementation packeData
- (id)init //simply initialise it
{
self = [super init];
if(self)
{
}
return self;
}
#end
and in view controller where u are tableview,
in ViewController.h
#import <UIKit/UIKit.h>
#import "packeData.h"
#interface ViewController : UIViewController <UI TableViewDataSource,UITableViewDelegate>
#property (weak, nonatomic) IBOutlet UITableView *aTableView;
#property (strong,nonatomic) NSMutableArray *recipes; //array acts as datasource
#end
in in ViewController.m
#import "ViewController.h"
#interface ViewController ()
#end
#implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
[[NSNotificationCenter defaultCenter]addObserver:self selector:#selector(theReciever:) name:#"theSender" object:nil];
_recipes = [[NSMutableArray alloc]init]; //initilise your datasource
for(int j = 0 ;j< 20;j++)
{
// for my example i took some values
//initially put some initial values
packeData *data = [[packeData alloc] init];
data.key = j;
data.process = [NSString stringWithFormat:#"game_name_%d",j];
[_recipes addObject:data];
}
}
- (void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
[NSTimer scheduledTimerWithTimeInterval:0.8 target:self selector:#selector(PostNotification) userInfo:nil repeats:YES]; //just for testing
}
- (void)PostNotification
{
//i am simply posting the notification with some random values
packeData *data = [[packeData alloc]init];
data.key = arc4random()%15;
data.process = [NSString stringWithFormat:#"%ld",( data.key + 20)];
[[NSNotificationCenter defaultCenter] postNotificationName:#"theSender" object:data];
}
- (void)theReciever:(NSNotification *)notif
{
if([notif.object isKindOfClass:[packeData class]]){
packeData *data=[notif object];
NSInteger key=data.key;
NSInteger index= key;
//modify the datasource
packeData *recipes_data = [_recipes objectAtIndex:index]; //get the pocket present in array
recipes_data.process = data.process; //modify the recipes data
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:index inSection:0];
UITableViewCell *cell=(UITableViewCell*)[self.aTableView cellForRowAtIndexPath:indexPath];
if(cell==nil)
{
NSLog(#"cell NULL");
}else
{
[self.aTableView reloadRowsAtIndexPaths:#[indexPath] withRowAnimation:UITableViewRowAnimationAutomatic];
// cell.textLabel.text=data.process; no need u already mofied the content in the datasource this will call the "cellForRowAtIndexPath" method and displays the process in place of game name
}
}else{
NSLog(#"ERR: object not recognised");
}
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return [_recipes count];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *simpleTableIdentifier = #"SimpleTableCell";
UITableViewCell* cell = [self.aTableView dequeueReusableCellWithIdentifier:simpleTableIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:simpleTableIdentifier];
NSLog(#"cell nil");
}
packeData *idgame= [_recipes objectAtIndex:indexPath.row];
cell.textLabel.text = idgame.process; //initially contains game name
cell.tag=indexPath.row;
return cell;
}
#end
EDIT
replace the below methods
- (void)PostNotification
{
//i am simply posting the notification with some random values
packeData *data = [[packeData alloc]init];
data.key = arc4random()%15; //15 change the number of rows
data.process = [NSString stringWithFormat:#"%ld",( data.key + arc4random() % 100)];
[[NSNotificationCenter defaultCenter] postNotificationName:#"theSender" object:data];
}
- (void)theReciever:(NSNotification *)notif
{
if([notif.object isKindOfClass:[packeData class]]){
packeData *data=[notif object];
NSInteger key=data.key;
NSInteger index= key;
//modify the datasource
packeData *recipes_data = [_recipes objectAtIndex:index]; //get the pocket present in array
recipes_data.process = data.process; //modify the recipes data
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:index inSection:0];
UITableViewCell *cell=(UITableViewCell*)[self.aTableView cellForRowAtIndexPath:indexPath];
if(cell==nil)
{
NSLog(#"cell NULL");
[self.aTableView reloadData]; //if cell is not visible then reload the whole table
}else
{
[self.aTableView reloadRowsAtIndexPaths:#[indexPath] withRowAnimation:UITableViewRowAnimationAutomatic];
// cell.textLabel.text=data.process; no need u already mofied the content in the datasource this will call the "cellForRowAtIndexPath" method and displays the process in place of game name
}
}else{
NSLog(#"ERR: object not recognised");
}
}
Edit 2
as for testing just change the below method and as soon as simulator launches the app scroll to down so that only top 5 rows only updates, wait for 5 to 10 seconds and scroll to top and u will see all the calls are updates with same process 5
//scroll down as soon as launches the app and wait for 5 to 10 seconds then scroll to top u will see top 5 cells are updates with progress 5
- (void)PostNotification
{
packeData *data = [[packeData alloc]init];
data.key = arc4random()%5; //only top 5 cells are modify other wont modify
data.process = [NSString stringWithFormat:#"%ld",5];//updates with some same progress lates give it as 5 //( data.key + arc4random() % 100)];
[[NSNotificationCenter defaultCenter] postNotificationName:#"theSender" object:data];
}
form the above test u will see the top 5 cells are updates even when they are not visible

Answer 2

You can't set the value of any of your cell's controller apart from cellForRowAtIndexPath you have to populate the UITableViewCell data with an array, then when you want to update the data in your cell, update your array according to data, then update the single cell of your UITableView like this.
[tableView beginUpdates];
[tableView reloadRowsAtIndexPaths:#[indexPathOfYourCell] withRowAnimation:UITableViewRowAnimationNone];
[tableView endUpdates];

Answer 3

Just specify your index path of your row and reload...
NSIndexPath* path = [NSIndexPath indexPathForRow:3 inSection:0];
NSArray* rowsToReload = [NSArray arrayWithObjects:path, nil];
[tableView reloadRowsAtIndexPaths:rowsToReload withRowAnimation:UITableViewRowAnimationNone];