Casting to right object for tableView cells - iphone

Question

I'm using tableView for displaying each tam tableView with different data.
when I coming back to the interface with all the tableView delegates i'm tantalizing the *list with a data (different arrays with fields) based on the the previous view
if(select = names )...
list = myData.Names;
if (select = workers)...
list = myData.Workers;
and so on...
and in the table delegates I use:
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
return [list count];
}
But when I initializing the object for the table cells, How can I set exatcly the right object for the cell. now hard-coded I using:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:#"MyIdentifier"] autorelease];
}
//HARD-CODED
names *s = [list objectAtIndex:indexPath.row];
cell.textLabel.text = names.firstName;
cell.detailTextLabel.text=s.lastName;
return cell;
}
When i setting the list to workers how can I know to cast every time to the right object? without writing millions of if?
for example if
if (select = workers)...
list = myData.Workers;
the [list count] will return the right number but i want to display data based on the list, how can i cast it so it automatically declare workers
workers *s = [list objectAtIndex:indexPath.row];

Answer 1

I think I understand your problem, so let me try to explain:
This can be easily solved using protocols and giving the cell configuring responsibility to the actual objects.
First, declare a protocol that your clases will conform to:
#class MyTableViewCell;
#protocol CellConfiguring
- (void)configureCell:(MyTableViewCell *)cell;
#end
Now make some classes and make sure all of them conform to this protocol:
#interface Workers : NSObject <CellConfiguring>
#property (retain, nonatomic) NSString *company;
#property (retain, nonatomic) NSString *salary;
#end
and:
#interface Names : NSObject <CellConfiguring>
#property (retain, nonatomic) NSString *firstName;
#property (retain, nonatomic) NSString *lastName;
#end
etc...
In their implementation, each of them will handle the configuring of the cell differently:
#import "MyTableViewCell.h"
#implementation Workers
- (void)configureCell:(MyTableViewCell *)cell
{
cell.textLabel.text = self.company;
cell.detailTextLabel.text = self.salary;
}
#end
and:
#import "MyTableViewCell.h"
#implementation Names
- (void)configureCell:(MyTableViewCell *)cell
{
cell.textLabel.text = self.firstName;
cell.detailTextLabel.text = self.lastName;
}
#end
Remember the cell you receive is a custom cell that you created. For instance:
#interface MyTableViewCell : UITableViewCell
#property (retain, nonatomic) UILabel *textLabel;
#property (retain, nonatomic) UILabel *detailTextLabel;
#end
Now, in your delegate call:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
MyTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:#"MyIdentifier"] autorelease];
}
id myObject = [list objectAtIndex:indexPath.row];
if ([myObject conformsToProtocol:#protocol(CellConfiguring)]
[myObject configureCell:cell];
return cell;
}
And that's it. No more if-else statements and no more casting.
Tip: Whenever you start seeing too many if-else statements in your class, dirtying up your code, start thinking about responsibilities. Should the object be in charge of figuring out how to configure the cell? Or could we delegate that task to another object?

Answer 2

Set One flag in .h file like BOOL flag. Data will be filled according flag.
Intially flag will be TRUE in ViewDidLoad.
Now set list like this:
if()...
listNames = myData.Names;
if ()...
listWorkers = myData.Workers;
and in the table delegates:
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
if(flag){
return [listNames count];
else
{
return [listWorkers count];
}
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:#"MyIdentifier"] autorelease];
}
if(flag)
{
names *s = [listNames objectAtIndex:indexPath.row];
cell.textLabel.text = names.firstName;
cell.detailTextLabel.text=s.lastName;
return cell;
}
else
{
names *s = [listWorkers objectAtIndex:indexPath.row];
cell.textLabel.text = names.firstName; // change for listWorkers
cell.detailTextLabel.text=s.lastName; // change for listWorkers
return cell;
}
}
Now when u want to change then
flag = FALSE; //worker data will be filled
[tableView reloadData]

Answer 3

You might be able to use the following solution ...
Create a custom object that conforms to UITableViewDataSource for each type of object. For example WorkerDataSource, NamesDataSource, etc...
Depending on the data you want to display, set the right dataSource for the tableView. An example from a project I work on ...
#define SECTION_HEADER_HEIGHT 20.0f
#interface FSMatchProgrammeDataSource ()
#property (nonatomic, copy) NSArray *matches;
#property (nonatomic, copy) NSArray *groupedMatches;
#end
#implementation FSMatchProgrammeDataSource
#synthesize matches = _matches;
#synthesize groupedMatches = _groupedMatches;
#synthesize didSelectMatchHandler = _didSelectMatchHandler;
+ (FSMatchProgrammeDataSource *)dataSourceWithMatches:(NSArray *)matches
{
FSMatchProgrammeDataSource *dataSource = [[FSMatchProgrammeDataSource alloc] init];
if (dataSource)
{
dataSource.matches = matches;
}
return dataSource;
}
#pragma mark - Table view data source
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return _groupedMatches.count;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
NSArray *matches = [_groupedMatches objectAtIndex:section];
return matches.count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"MatchProgrammeCellIdentifier";
FSMatchProgrammeCell *cell = (FSMatchProgrammeCell *)[tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (!cell)
{
cell = [[FSMatchProgrammeCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}
NSArray *matches = [_groupedMatches objectAtIndex:indexPath.section];
cell.match = [matches objectAtIndex:indexPath.row];
DLog(#"%#", cell.match);
return cell;
}
#pragma mark - Table view delegate
- (UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section
{
// custom view created here ...
}
- (CGFloat)tableView:(UITableView *)tableView heightForHeaderInSection:(NSInteger)section
{
return SECTION_HEADER_HEIGHT;
}
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
return 44.0f;
}
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
if (_didSelectMatchHandler)
{
NSArray *matches = [_groupedMatches objectAtIndex:indexPath.section];
FSMatch *match = [matches objectAtIndex:indexPath.row];
_didSelectMatchHandler(match);
}
}
#pragma mark - Properties
- (void)setMatches:(NSArray *)matches
{
// matches property set, also an sorted / grouped copy is created for display called groupMatches ...
}
#end
And the dataSource is assigned in the tableViewController like this:
- (void)refreshView
{
BOOL showInfoLabel = NO;
switch (_tabBar.selectedSegmentTag)
{
case TabProgramme:
_tableView.dataSource = _programmeDataSource;
_tableView.delegate = _programmeDataSource;
break;
case TabResults:
_tableView.dataSource = _resultsDataSource;
_tableView.delegate = _resultsDataSource;
break;
case TabStandings:
_tableView.dataSource = _standingsDataSource;
_tableView.delegate = _standingsDataSource;
break;
default: break;
}
[self.tableView reloadData];
}