I am trying to get new cells with data from a NSManagedObject to a tableview with a fixed section.
The first section is a fixed section. The second section is where the user can add new data. Displaying the fixed section separate is no problem, as well as showing the dynamic content separate. But when I combine them, I get stuck with this method (see below at the 'rows = ???'). Normally you can fix this easily by doing [array count] but my ManagedObjects are not collected in an array.
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
//id <NSFetchedResultsSectionInfo> sectionInfo = [[self.fetchedResultsController sections] objectAtIndex:section];
//return [sectionInfo numberOfObjects];
NSInteger rows = 0;
switch (section) {
case FIXED_SECTION:
rows = 4;
break;
case LIST_SECTION:
{
rows = ???;
break;
}
default:
break;
}
return rows;
}
Either collect the NSManagedObjects in an array (probably an instance variable of the view controller subclass you’re using) or maintain a counter that you increment when adding a cell and decrement when you remove a cell.
The NSFetchedResultsController is what you need, the manual section explains pretty much as you need it
Related
In one section of my app I have a UITableView which is working fine right now. I would like to set row 0 cell.textLabel.text to #"Some string". Once row 0 has been set I would then like to load the rest of the rows from an array. Currently on load my array populates the table view but I'm trying to set row 0 as a sticky. The closest example I can think of is a forum topic that is set to stay at the top. My array is constructed of returned data from a web service call.
It's been a while since I've messed with table views, and I'm having a blank on this one.
The table view is 1 section, and I get the rows by counting the elements in the array. Since I would like to create an additional cell (row 0) I would call [array count] + 1. I don't know if this approach is the best one which is why I'm reaching out to the community here.
Any insight or a shove in the right direction would be great at this point.
You're on the right track:
-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
return [array count]+1;
}
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:#"Cell"];
if ([indexPath row] == 0) {
// Code for first
[[cell textLabel] setText:#"First cell"];
} else {
[[cell textLabel] setText:[array objectAtIndex:[indexPath row]-1]];
}
return cell;
}
If you want the top of your table to be "sticky", why not consider using that string as a section header or title? In this case, the header stays visible at all times until the next section (e.g. if you had two sections, that is) is fully on the screen.
In any event, in one of my current projects I'm required to do roughly the same thing that you're doing and I have a static string being returned in row 0 (which scrolls off the top of screen when the table view scrolls down).
And in my UITableViewDataSource method, I always add one for the static cell to the number of objects in my array and in my "cellForRowAtIndexPath:" method, I increment the row by one when the indexPath.row is not zero. And if it is zero, I return my static string.
And dark_knight provides some nice sample code that illustrates what I was describing to you. So +1 to him/her.
I am using grouped tableview for developing a contact list using database. I have to show the message "No Contacts" on tableview when there is no contact in list. how can I do it?
Share your ideas..
Thanks in Advance
supposing that you are using an array to store all the contacts then use the following delegate
-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
// You can also modify this condition according to a specific section
if([YOUR_ARRAY count] == 0)
{
return 1;
}
else
return [YOUR_ARRAY count];
}
Now adding data to table in following delegate
-(UITableViewCell*)tableView:(UITableView*)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
// Initialise your cell
if([YOUR_ARRAY count] > 0){
// add your array data to cells
}
if([YOUR_ARRAY count] == 0){
// this means no contacts in array and therfore you have only one cell to display NO CONTACTS
}
return cell;
}
For cases like this one we used table headers.
If the table had elements in his data source, the table header was clear and had a 1px height.
If the data source had no elements, then the table header view was set as big as the table's frame and contained a message, an image or whatever you might need.
The functions (table view delegate methods, actually) we used were height for header in section and view for header in section. We verified the data source inside the viewForHeader function
You can achieve the same effect using the table footers as well
you can add UILabel
ande set the text of the label
label.text = #"No results ";
and you make a test
if ([contacts count] == 0)
{
yourTableview.hidden = YES;
yourLabel.hidden = NO;
}
else
{
yourTableview.hidden = NO;
yourLabel.hidden = YES;
}`
All,
I have a grouped UITableView with a possible total of 3 sections. There could be 1, 2 or 3.
My issue is that for each section I use a different header & footer view. I am choosing which header/footer to show by checking the section #.
This obviously does not work, as section 0 does not always represent what 'header' 0 shows.
Example:
Header #0 = "Game in progress". But no games in progress are returned from the database. Only 'Games Ended" exist. Therefore section 0 would be all 'games ended'. I don't want 'Games Ended' to use the 'Games in Progress' header.
I can't find a way to check the section value, and not the number.
To put it simply, I would like to be able to show section header #3 for section name #3, even if section name #3 is section #0.
I know this seems trivial, and is probably simple... but I am stuck. Any help is appreciated.
Thanks.
----- CODE -----
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
return [[fetchedResultsController_ sections] count];
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
id <NSFetchedResultsSectionInfo> sectionInfo = [[fetchedResultsController_ sections] objectAtIndex:section];
return [sectionInfo numberOfObjects];
}
- (CGFloat)tableView:(UITableView *)tableView heightForHeaderInSection:(NSInteger)section {
if(section == 0)
{
return 50.0f;
}
else if (section == 1)
return 50.0f;
else
return 50.0f;
}
- (CGFloat)tableView:(UITableView *)tableView heightForFooterInSection:(NSInteger)section {
if(section == 0 )
{
return 50.0f;
}
else if (section == 1)
return 5.0f;
else
return 80.0f;
}
- (UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section {
if(section == 0)
{
return headerView1;
}
else if (section == 1)
return headerView2;
else
return headerView3;
}
- (UIView *)tableView:(UITableView *)tableView viewForFooterInSection:(NSInteger)section {
if(section == 0)
{
return footerView1;
}
else if (section == 1)
return footerView2;
else
return footerView3;
}
Obviously, deciding which header / footer to show by checking the section # is wrong (this is bad MVC). For a solution to your problem, it would be better to see some actual code, although I think I can suggest something in general:
The sections that you show are taken out of some data source - an array, a dictionary or some other collection (this is the same collection you use to determine, for example, the return value for the numberOfSectionsInTableView: delegate method. If you haven't done so already, you should incorporate these data instances into some object that contains the data itself (this is the data that you normally need for displaying the cell/header/footer elements along with the actual data values) - In this object, add an additional "HeaderType" enumerated value, so that each object "knows" how it is supposed to be displayed. This way your MVC is perfect: You have your data stored in a collection of custom objects, your controller knows how to display the data by it's type and of course your view shows the data properly based on the controller's instructions.
Here is an example of an enumeration that could help:
typedef enum {
kHeaderTypeGameProgress,
kHeaderTypeGameStats,
kHeaderTypeGameDate
} HeaderType;
In your "viewForHeader" or "viewForFooter" methods, just add a switch type to check the data's HeaderType and create a view accordingly. Hope I helped, good luck!
It seems that in your cellForRowAtIndexPath, you must already have some logic that decides what group to show data from, maybe something like:
NSArray *group;
int section = indexPath.section;
if (![gamesInProgress count]) section++;
switch (section) {
case 0:
group = gamesInProgress;
break;
case 1:
group = finishedGames;
break;
// etc.
}
In your viewForHeaderInSection, write similar code that sets a NSString instead of NSArray.
I am implementing a table index view and amazed to see how my table indexes are working even without implementing:
- (NSInteger)tableView:(UITableView *)tableView sectionForSectionIndexTitle:(NSString *)title atIndex:(NSInteger)index method.
I have only implemented:
- (NSArray *)sectionIndexTitlesForTableView:(UITableView *)tableView
Strangely, when I am running in breakpoints, Once i click on any of the index values my
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
method is getting called.
Any clue why this is so happening and what is the significance of sectionForSectionIndexTitle method then.
if you have a list of all letters in alphabet and your list only contains some entries, you could use the following code:
//Asks the data source to return the index of the section having the given title and section title index.
- (NSInteger)tableView:(UITableView *)tableView sectionForSectionIndexTitle:(NSString *)title atIndex:(NSInteger)index {
if (tableView == self.searchDisplayController.searchResultsTableView || self.searchBar.text.length > 0)
{
return 0;
}
else
{
//direct - firsttime match
if([self.realMIndexArray containsObject:title]) {
NSInteger count = 0;
for(NSString *character in self.realMIndexArray)
{
if([character isEqualToString:title]){
return count;
}
count ++;
}
}
else {
//take next higher letter from alphabet and check if its contained in the "available letters list"
//if not, select last entry of list
for(int i = [self.indexArray indexOfObject:title] + 1; i < [self.indexArray count]; i++) {
NSString* character = [self.indexArray objectAtIndex:i];
if([self.realMIndexArray containsObject:character]) {
return [self.realMIndexArray indexOfObject:character];
}
}
return [self.realMIndexArray count] - 1;
}
return 0;// in case of some eror donot crash d application
}
}
realMIndexArray count == letters really existing in list
indexArray = list of all letters in alphbeth.
hope this helps someone (took me a little bit of time to figure it out)
Any clue why this is so happening
Yes. When you tap (you do not click on an iPhone) on a table's index, the underlying table view will want to jump to that section, and the cells in that section. In order to do that, it has to ask the data source for those cells so it can render them on the screen.
what is the significance of
sectionForSectionIndexTitle method
then.
The documentation for tableView:sectionForSectionIndexTitle:atIndex: (which is an optional method in the UITableViewDataSource protocol) says:
Asks the data source to return the
index of the section having the given
title and section title index.
and
You implement this method only for
table views with a section index
list—which can only be table views
created in the plain style
(UITableViewStylePlain).
Does this apply for your UITableView? In other words, are you using a grouped table view style?
Update
I have posted my solution to this problem as an answer below. It takes a different approach from my first revision.
Original Question
I previously asked a question on SO that I thought solved my issues:
How to deal with non-visible rows during row deletion. (UITableViews)
However, I now have similar problems again when removing sections from a UITableView.
(they resurfaced when I varied the number of sections/rows in the table).
Before I lose you because of the shear length of my post, let me state the problem clearly, and you can read as much as you require to provide an answer.
Problem:
If batch deleting rows AND sections from a UITableView, the application crashes, sometimes. It depends on the configuration of the table and the combination of rows and sections I choose to remove.
The log says I crashed because it says I have not updated the datasource and the table properly:
Invalid update: invalid number of rows in section 5. The number of rows contained in an existing section after the update (2) must be equal to the number of rows contained in that section before the update (1), plus or minus the number of rows inserted or deleted from that section (0 inserted, 0 deleted).
Now quickly, before you write the obvious answer, I assure you I have indeed added and deleted the rows and sections properly from the dataSource. The explanation is lengthy, but you will find it below, following the method.
So with that, if you are still interested…
Method that handles removal of sections and rows:
- (void)createFilteredTableGroups{
//index set to hold sections to remove for deletion animation
NSMutableIndexSet *sectionsToDelete = [NSMutableIndexSet indexSet];
[sectionsToDelete removeIndex:0];
//array to track cells for deletion animation
NSMutableArray *cellsToDelete = [NSMutableArray array];
//array to track controllers to delete from presentation model
NSMutableArray *controllersToDelete = [NSMutableArray array];
//for each section
for(NSUInteger i=0; i<[tableGroups count];i++){
NSMutableArray *section = [tableGroups objectAtIndex:i];
//controllers to remove
NSMutableIndexSet *controllersToDeleteInCurrentSection = [NSMutableIndexSet indexSet];
[controllersToDeleteInCurrentSection removeIndex:0];
NSUInteger indexOfController = 0;
//for each cell controller
for(ScheduleCellController *cellController in section){
//bool indicating whether the cell controller's cell should be removed
NSString *shouldDisplayString = (NSString*)[[cellController model] objectForKey:#"filteredDataSet"];
BOOL shouldDisplay = [shouldDisplayString boolValue];
//if it should be removed
if(!shouldDisplay){
NSIndexPath *cellPath = [self indexPathOfCellWithCellController:cellController];
//if cell is on screen, mark for animated deletion
if(cellPath!=nil)
[cellsToDelete addObject:cellPath];
//marking controller for deleting from presentation model
[controllersToDeleteInCurrentSection addIndex:indexOfController];
}
indexOfController++;
}
//if removing all items in section, add section to removed in animation
if([controllersToDeleteInCurrentSection count]==[section count])
[sectionsToDelete addIndex:i];
[controllersToDelete addObject:controllersToDeleteInCurrentSection];
}
//copy the unfiltered data so we can remove the data that we want to filter out
NSMutableArray *newHeaders = [tableHeaders mutableCopy];
NSMutableArray *newTableGroups = [[allTableGroups mutableCopy] autorelease];
//removing controllers
int i = 0;
for(NSMutableArray *section in newTableGroups){
NSIndexSet *indexesToDelete = [controllersToDelete objectAtIndex:i];
[section removeObjectsAtIndexes:indexesToDelete];
i++;
}
//removing empty sections and cooresponding headers
[newHeaders removeObjectsAtIndexes:sectionsToDelete];
[newTableGroups removeObjectsAtIndexes:sectionsToDelete];
//update headers
[tableHeaders release];
tableHeaders = newHeaders;
//storing filtered table groups
self.filteredTableGroups = newTableGroups;
//filtering animation and presentation model update
[self.tableView beginUpdates];
tableGroups = self.filteredTableGroups;
[self.tableView deleteSections:sectionsToDelete withRowAnimation:UITableViewRowAnimationTop];
[self.tableView deleteRowsAtIndexPaths:cellsToDelete withRowAnimation:UITableViewRowAnimationTop];
[self.tableView endUpdates];
//marking table as filtered
self.tableIsFiltered = YES;
}
My guess:
The problem seems to be this: If you look above where I list the number of cells in each section, you will see that section 5 appears to increase by 1. However, this is not true. The original section 5 has actually been deleted and another section has taken its place (specifically, it is old section 10).
So why does the table view seem not to realize this? It should KNOW that I removed the old section and should not expect a new section that is now located at the old section's index to be bound by the deleted section's number of rows.
Hopefully this makes sense, it is a little complicate to write this out.
(note this code worked before with a different number of rows/sections. this particular configuration seems to give it issues)
I’ve run into this problem before. You are trying to delete all rows from a section and then, in addition, that now empty section. However, it is sufficient (and proper) to remove that section only. All rows within it will be removed as well. Here is some sample code from my project that handles deletion of one row. It needs to determine whether it should remove only this row from a section or delete the entire section if it is the last remaining row in that section:
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
if (editingStyle == UITableViewCellEditingStyleDelete)
{
// modelForSection is a custom model object that holds items for this section.
[modelForSection removeItem:[self itemForRowAtIndexPath:indexPath]];
[tableView beginUpdates];
// Either delete some rows within a section (leaving at least one) or the entire section.
if ([modelForSection.items count] > 0)
{
// Section is not yet empty, so delete only the current row.
[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath]
withRowAnimation:UITableViewRowAnimationFade];
}
else
{
// Section is now completely empty, so delete the entire section.
[tableView deleteSections:[NSIndexSet indexSetWithIndex:indexPath.section]
withRowAnimation:UITableViewRowAnimationFade];
}
[tableView endUpdates];
}
}
I notice that you're deleting the sections from the table first, and then deleting rows.
I know there's a complicated discussion of batch insertion and deletion for UITableViews in the Table View Programming Guide, but it doesn't specifically cover this.
I think what's happening is that deleting the sections is causing the row deletions to refer to the wrong row.
i.e. you want to delete section #2 and row #1 from section #4... but after you've deleted section #2, the old section #4 is now the third section, so you when you delete with the old NSIndexPath of (4, 1) you're deleting some random different row that may not exist.
So I think the fix might be as simple as swapping those two lines of code, so you're deleting the rows first, then the sections.
So finally here is my solution to this issue.
This method can be applied to tables of any size, any number of sections (as far as I can tell)
As before I have modified Matt Gallagher's tableview Code which places cell-specific logic in a separate cell controller. However, you can easily adapt this method to a different model
I have added the following (relevant) ivars to Matt's code:
NSArray *allTableGroups; //always has a copy of every cell controller, even if filtered
NSArray *filteredTableGroups; //always has a copy of the filtered table groups
Matt's original ivar:
NSArray *allTableGroups
…always points to one of the above arrays.
This can probably be refactored and improved significantly, but I haven't had the need. Also, if you use Core Data, NSFetchedResultsController makes this easier.
Now on to the method (I am trying to comment as much as I can):
- (void)createFilteredTableGroups{
//Checking for the usual suspects. all which may through an exception
if(model==nil)
return;
if(tableGroups==nil)
return;
if([tableGroups count]==0)
return;
//lets make a new array to work with
NSMutableArray *newTableGroups = [[allTableGroups mutableCopy] autorelease];
//telling the table what we are about to do
[self.tableView beginUpdates];
//array to track cells for deletion animation
NSMutableArray *indexesToRemove = [NSMutableArray array];
//loop through each section
for(NSMutableArray *eachSection in tableGroups){
//keeping track of the indexes to delete for each section
NSMutableIndexSet *indexesForSection = [NSMutableIndexSet indexSet];
[indexesForSection removeAllIndexes];
//increment though cell indexes
int rowIndex = 0;
//loop through each cellController in the section
for(ScheduleCellController *eachCellController in eachSection){
//Ah ha! A little magic. the cell controller must know if it should be displayed.
//This you must calculate in your business logic
if(![eachCellController shouldDisplay]){
//add non-displayed cell indexes
[indexesForSection addIndex:rowIndex];
}
rowIndex++;
}
//adding each array of section indexes, EVEN if it is empty (no indexes to delete)
[indexesToRemove addObject:indexesForSection];
}
//Now we remove cell controllers in newTableGroups and cells from the table
//Also, each subarray of newTableGroups is mutable as well
if([indexesToRemove count]>0){
int sectionIndex = 0;
for(NSMutableIndexSet *eachSectionIndexes in indexesToRemove){
//Now you know why we stuck the indexes into individual arrays, easy array method
[[newTableGroups objectAtIndex:sectionIndex] removeObjectsAtIndexes:eachSectionIndexes];
//tracking which cell indexPaths to remove for each section
NSMutableArray *indexPathsToRemove = [NSMutableArray array];
int numberOfIndexes = [eachSectionIndexes count];
//create array of indexPaths to remove
NSUInteger index = [eachSectionIndexes firstIndex];
for(int i = 0; i< numberOfIndexes; i++){
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:index inSection:sectionIndex];
[indexPathsToRemove addObject:indexPath];
index = [eachSectionIndexes indexGreaterThanIndex:index];
}
//delete the rows for this section
[self.tableView deleteRowsAtIndexPaths:indexPathsToRemove withRowAnimation:UITableViewRowAnimationTop];
//next section please
sectionIndex++;
}
}
//now we figure out if we need to remove any sections
NSMutableIndexSet *sectionsToRemove = [NSMutableIndexSet indexSet];
[sectionsToRemove removeAllIndexes];
int sectionsIndex = 0;
for(NSArray *eachSection in newTableGroups){
//checking for empty sections
if([eachSection count]==0)
[sectionsToRemove addIndex:sectionsIndex];
sectionsIndex++;
}
//updating the table groups
[newTableGroups removeObjectsAtIndexes:sectionsToRemove];
//removing the empty sections
[self.tableView deleteSections:sectionsToRemove withRowAnimation:UITableViewRowAnimationTop];
//updating filteredTableGroups to the newTableGroups we just created
self.filteredTableGroups = newTableGroups;
//pointing tableGroups at the filteredGroups
tableGroups = filteredTableGroups;
//invokes the animation
[self.tableView endUpdates];
}
I saw this same exact error as the result of prematurely releasing the background view of my custom tableview cell.
With NSZombieEnabled I got a an exception being thrown way down below an internal call to a function to prepare the cell for reuse. Without NSZombieEnabled, I was getting the Internal consistency error.
Incidentally when I fixed the retain/release issue on the background view of the cell, I was able to delete the last row of the section without having to delete the section explicitly.
Moral of the story: This error just means something bad is happening when you try to delete, and one of the things that happens when you delete is the cell gets prepared for reuse, so if you are doing anything custom with your tableview cells, look for a possible error there.
I suspect that you are forgetting to remove the object representing the section from your internal storage, so that the -numberOfSectionsInTableView: method is still returning 1 after all sections are deleted.
That's exactly what I was doing wrong when I had the same crash!
A much simpler way to address this is to update your data source, then call reloadSections
[self.tableView reloadSections:[NSIndexSet indexSetWithIndex:0] withRowAnimation:UITableViewRowAnimationFade];
This will reload a single section. Alternatively you could use indexSetWithIndexesInRange: to reload multiple sections simultaneously.
or just do this
- (void)tableView:(UITableView *)tv
commitEditingStyle:(UITableViewCellEditingStyle)editingStyle
forRowAtIndexPath:(NSIndexPath *)indexPath {
if(editingStyle == UITableViewCellEditingStyleDelete) {
//Delete the object from the table.
[directoriesOfFolder removeObjectAtIndex:indexPath.row];
[tv deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath]
withRowAnimation:UITableViewRowAnimationFade];
}
}
directories of folder being your Array! Thats is all above codes didnt work for me! This is less expensive to do and just makes sense!