I've got some (I think) pretty basic code for creating cell content from a data source, and everything works fine when the display loads. However, when I start scrolling around to view other text (up or down) the code fails with 'GDB: Program received signal: "EXEC_BAD_ACCESS"'. Here's the code that fills out the display for the various sections; each section has similar code:
id cell = (UITableViewCell *)[tableView
dequeueReusableCellWithIdentifier:CellIdentifier
];
titledCell = [[[TitledCell alloc]
initWithFrame:CGRectZero
reuseIdentifier:CellIdentifier
] autorelease
];
switch (tableSection) {
case TABLE_SECTION_1:
if (cell == nil) {
dataKey = #"a key from data source";
dataFromSource = [viewData objectForKey:dataKey];
titledCell.title.text = dataKey;
titledCell.contents.text = dataFromSource;
cell = titledCell;
break;
}
case TABLE_SECTION_2:
...
}
return cell;
As I was following the code, I noticed that the code skips the cell creation when scrolling the cell back into view, because cell != nil. If it skips, that means that cell contains the same contents as the first time it was created, right? Why is giving me trouble?
I usually get EXEC_BAD_ACCESS when I forget to retain something. If you've got an autorelased object, it may work the first time through but not work the second time.
Run the program with debugging and use Xcode to figure out what line it's crashing on. That will be more helpful than anything else.
I think the EXEC_BAD_ACCESS might caused by the:
titledCell.title.text = dataKey;
titledCell might get dealloced and when accessing the property there'll be a EXEC_BAD_ACCESS exception.
You can turn on the NSZombieEnabled env virable in: Group & Files -> Extutables -> Your App -> Get Info -> Arguments
Can't be 100% sure with the code sample you've given but a good guess would be the break statement is within the if block. So it should look like:
switch( tableSection ) {
case TABLE_SECTION_1:
if( cell == nil ) {
dataKey = #"a key from data source";
dataFromSource = [ viewData objectForKey:dataKey ];
titledCell.title.text = dataKey;
titledCell.contents.text = dataFromSource;
cell = titledCell;
}
break;
case TABLE_SECTION_2:
...
}
Unfortunately, changes have made this question academic, so I can't really tell if any of the answers given are correct. The current code looks a little closer to this:
id cell = (UITableViewCell *)[tableView
dequeueReusableCellWithIdentifier:CellIdentifier
];
if (cell == nil) {
titledCell = [[[TitledCell alloc]
initWithFrame:CGRectZero
reuseIdentifier:CellIdentifier
] autorelease
];
switch (tableSection) {
case TABLE_SECTION_1:
dataKey = #"a key from data source";
dataFromSource = [viewData objectForKey:dataKey];
titledCell.title.text = dataKey;
titledCell.contents.text = dataFromSource;
cell = titledCell;
break;
case TABLE_SECTION_2:
...
}
return cell;
...so that most of the code is now in the "if (cell == nil)" block (which makes more sense), and it works fine. I wish I understood what was wrong, but thanks for your Answers anyway!
Related
I'm trying to covert Speakrbox code in Objective-C.
I have already converted most of the code but I have a little problem with this one:
private func updateCallDurationForVisibleCells() {
/*
Modify all the visible cells directly, since -[UITableView reloadData] resets a lot
of things on the table view like selection & editing states
*/
let visibleCells = tableView.visibleCells as! [CallSummaryTableViewCell]
guard let indexPathsForVisibleRows = tableView.indexPathsForVisibleRows else { return }
for index in 0..<visibleCells.count {
let cell = visibleCells[index]
let indexPath = indexPathsForVisibleRows[index]
guard let call = call(at: indexPath) else { return }
cell.durationLabel?.text = durationLabelText(forCall: call)
}
}
I tried to convert it, and here is what I have:
-(void) updateCallDurationForVisibleCells :(id)sender {
/*
Modify all the visible cells directly, since -[UITableView reloadData] resets a lot
of things on the table view like selection & editing states
*/
_visibleCells = _tableview.visibleCells;
if(_indexPathsForVisibleRows == _tableview.indexPathsForVisibleRows) { return ; }
int index;
for (index=0; index<_visibleCells.count; index ++)
{
UICollectionViewCell *cell = _visibleCells[index];
NSIndexPath *indexPath = _indexPathsForVisibleRows[index];
UITableViewCell* call;
if((call = [self.tableView cellForRowAtIndexPath:indexPath]))
{ return ; }
}
}
Could any one please help me to convert this Swift code into Objective-C? The code doesn't compile for the reason that I didn't know how to convert this line of code:
cell.durationLabel?.text = durationLabelText(forCall: call)
Also, I don't know if I did it in the right way, especially the conversion of guard let.
you will find here Call and durationLabelText functions that I have used in pdateCallDurationForVisibleCells function:
private func call(at indexPath: IndexPath) -> SpeakerboxCall? {
return callManager?.calls[indexPath.row]
}//swift
private func durationLabelText(forCall call: SpeakerboxCall) -> String? {
return call.hasConnected ? callDurationFormatter.format(timeInterval: call.duration) : nil
}//Swift
Here's a fixed up version of your Objective-C code. Please note that when you see var or let in Swift, you are creating a local variable. Do not create a bunch a needless instance variables or properties in the Objective-C code when you should just use local variables.
- (void)updateCallDurationForVisibleCells {
/*
Modify all the visible cells directly, since -[UITableView reloadData] resets a lot
of things on the table view like selection & editing states
*/
NSArray *indexPathsForVisibleRows = self.tableView.indexPathsForVisibleRows;
if(!indexPathsForVisibleRows) { return ; }
NSArray *visibleCells = self.tableview.visibleCells;
for (NSInteger index = 0; index < _visibleCells.count; index++) {
CallSummaryTableViewCell *cell = visibleCells[index];
NSIndexPath *indexPath = indexPathsForVisibleRows[index];
SomeDataType *call = [self call:indexPath];
if (!call) { return; }
cell.durationLabel.text = [self durationLabelText:call];
}
}
There is some information missing which means this conversion may not be 100% correct.
You haven't shown the Objective-C signature of the call: method so I can't be sure how to call it properly and I don't know what data type to use for the call variable. Replace SomeDataType with the proper type.
You haven't shown the Objective-C signature of the durationLabelText: method so I can't be 100% sure about the proper way to call it.
If you post those details in your question I can be sure this answer is updated properly.
Edit: Thanks to users like #rmaddy, newbies like me get to learn how to write answers.Adding the final full code part.
Skip to the final part of the answer to get the working code.
In case you want to know where you went wrong, read the full answer.
There are multiple things that are possibly not right here, let me address what I know:
The guard statement is used for graceful exit. I'm no Java expert, but consider this to be like Exceptions in JAVA. The Obj-C code for your first guard would be:
if (nil == _tableview.indexPathsForVisibleRows){
return
}
This also means that there's no necessity for the _indexPathsForVisibleRows variable.
I'd recommend this article to understand guard better:
https://ericcerney.com/swift-guard-statement/
With respect to your second guard, please pay attention to detail.
call(at: indexPath) is not the same as cellForRowAtIndexPath.
call(at: indexPath) is a class function that returns a datatype, say CallType. cellForRowAtIndexPath is a UITableView function, that returns a cell.
The cell in the below line is more likely to be of type CallSummaryTableViewCell
UICollectionViewCell *cell = _visibleCells[index];
Regarding durationLabelText(), it seems to be a class function in the swift file whose declaration would be something like:
//Assume the type of "call" is CallType
private func durationLabelText(forCall call : CallType) -> String{
//your code here
}
The Objective-C equivalent would be:
-(NSString*) durationLabelTextForCall: (id<CallType>) call{
//your code here
}
The Objective-C call would be:
cell.durationLabel.text = [self durationLabelTextForCall: call]
So, the final code would be like this:
-(NSString*) durationLabelTextForCall: (id<CallType>) call{
//your code here
}
-(id<CallType>) callAtIndexPath:(NSIndexPath) indexPath{
//your code here
}
- (void)updateCallDurationForVisibleCells {
/*
Modify all the visible cells directly, since -[UITableView reloadData] resets a lot
of things on the table view like selection & editing states
*/
if (nil == _tableview.indexPathsForVisibleRows){
return
}
NSArray *visibleCells = self.tableview.visibleCells;
for (index=0; index<visibleCells.count; index ++)
{
CallSummaryTableViewCell *cell = visibleCells[index];
NSIndexPath *indexPath = _tableview.indexPathsForVisibleRows[index];
id<CallType> call = [self callAtIndexPath:indexPath];
if (nil == call){
return
}
cell.durationLabel.text = [self durationLabelTextForCall: call]
}
}
I'm trying to implement a system that changes a label based on the state of an NSPopUpButton.
So far I've tried to do what's displayed in the code below, but whenever I run it, the code just jumps into the else clause, throwing an alert
- (IBAction)itemChanged:(id)sender {
if([typePopUp.stringValue isEqualToString: #"Price per character"]) {
_currency = [currencyField stringValue];
[additionalLabel setStringValue: _currency];
}
else if([typePopUp.stringValue isEqualToString: #"Percent saved"]) {
_currency = additionalLabel.stringValue = #"%";
}
else alert(#"Error", #"Please select a calculation type!");
}
So does anyone here know what to do to fix this?
#hamstergene is on the right track, but is comparing the title of the menu item rather than, say, the tag, which is wrong for the following reasons:
It means you cannot internationalize the app.
It introduces the possibility of spelling mistakes.
It's an inefficient comparison; comparing every character in a string takes way longer than comparing a single integer value.
Having said all that, NSPopUpButton makes it difficult to insert tags into the menu items, so you need to use the index of the selected item:
Assume you create the menu items using:
[typePopUp removeAllItems];
[typePopUp addItemsWithTitles: [NSArray arrayWithObjects: #"Choose one...", #"Price per character", #"Percent saved", nil]];
Then create an enum that matches the order of the titles in the array:
typedef enum {
ItemChooseOne,
ItemPricePerCharacter,
ItemPercentSaved
} ItemIndexes;
And then compare the selected item index, as follows:
- (IBAction)itemChanged:(id)sender {
NSInteger index = [(NSPopUpButton *)sender indexOfSelectedItem];
switch (index) {
case ItemChooseOne:
// something here
break;
case ItemPricePerCharacter:
_currency = [currencyField stringValue];
[additionalLabel setStringValue: _currency];
break;
case ItemPercentSaved:
_currency = #"%"; // See NOTE, below
additionalLabel.stringValue = #"%";
break;
default:
alert(#"Error", #"Please select a calculation type!");
}
}
NOTE the following line was incorrect in your code:
_currency = additionalLabel.stringValue = #"%";
Multiple assignment works because the result of x = y is y. This is not the case when a setter is involved. The corrected code is above.
EDIT This answer was heavily edited following more info from the OP.
To query the title of currently selected item in NSPopUpButton:
NSMenuItem* selectedItem = [typePopUp selectedItem];
NSString* selectedItemTitle = [selectedItem title];
if ([selectedItemTitle isEqualTo: ... ]) { ... }
Note that comparing UI strings is a very bad idea. A slightest change in UI will immediately break your code, and you are preventing future localization. You should assign numeric or object values to each item using -[NSMenuItem setTag:] or -[NSMenuItem setRepresentedObject:] and use them to identify items instead.
I integrated GrabKit in my iPhone-App, which is a Library to Grab Photos from social Networks. Now I have the following situation/problem:
I have a UITableViewController - AlbumListViewController.
Then there's a UITableViewCell - AlbumCellViewController.
When you tap on one of these cells - albums with photos
There's a UITableViewController - PhotoListViewController
and a UITableViewCell - PhotoCellViewController.
Everything here works just finde, I can browse albums, choose one, browse the photos in it and then when I choose one of the single photos, there is a PushViewController to my SetPhotoViewController, which displays the selected image in Fullscreen.
Now when I want to use the back-Button of my navigation bar in the SetPhotoViewController, the crashes with the following message:
*** Assertion failure in -[UISectionRowData refreshWithSection:tableView:tableViewRowData:], /SourceCache/UIKit_Sim/UIKit-2372/UITableViewRowData.m:400
2012-10-22 22:49:32.814 Amis[1820:c07] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Failed to allocate data stores for 1073741821 rows in section 1. Consider using fewer rows'
*** First throw call stack:
(0x23de012 0x1b63e7e 0x23dde78 0x15f9f35 0xc8f83b 0xc923c4 0xb56fa2 0xb5692c 0x1690f 0x1cd653f 0x1ce8014 0x1cd87d5 0x2384af5 0x2383f44 0x2383e1b 0x2a9a7e3 0x2a9a668 0xaab65c 0x42fd 0x2b75)
libc++abi.dylib: terminate called throwing an exception
DataSource and Delegate of my two UITableViewControllers are both set to File's Owner.
When I debug trough the code, I can't find any special things, all photos can be loaded, all the arrays are filled with data, there's nothing strange.
Here are the two functions of the PhotoListViewController which get called, as soon as I press the back button on my NavigationController:
(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell *cell = nil;
NSLog(#"%i", indexPath.row);
NSLog(#"%ii", indexPath.section);
// Extra Cell
if ( indexPath.section > _lastLoadedPageIndex ){
static NSString *extraCellIdentifier = #"ExtraCell";
cell = [tableView dequeueReusableCellWithIdentifier:extraCellIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:extraCellIdentifier];
}
cell.textLabel.text = #"load more";
cell.textLabel.font = [UIFont fontWithName:#"System" size:8];
} else {
static NSString *photoCellIdentifier = #"photoCell";
cell = [tableView dequeueReusableCellWithIdentifier:photoCellIdentifier];
if (cell == nil) {
cell = [[[NSBundle mainBundle] loadNibNamed:#"PhotoRowViewController" owner:self options:nil] objectAtIndex:0];
}
}
// setting of the cell is done in method [tableView:willDisplayCell:forRowAtIndexPath:]
return cell;
}
and..
- (void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath
{
// extra cell
if ( [cell.reuseIdentifier isEqualToString:#"ExtraCell"] ){
if ( state == GRKDemoPhotosListStateAllPhotosGrabbed ) {
cell.textLabel.text = [NSString stringWithFormat:#" %d photos", [[_album photos] count] ];
}else {
cell.textLabel.text = [NSString stringWithFormat:#"Loading page %d", _lastLoadedPageIndex+1];
[self fillAlbumWithMorePhotos];
}
} else // Photo cell
{
NSArray * photosAtIndexPath = [self photosForCellAtIndexPath:indexPath];
[(PhotoRowViewController*)cell setPhotos:photosAtIndexPath];
}
}
What am I missing?
Edit: The code of the numberOfRowsInSection-Method:
If I debug it, the first time res is equal 0, the second time the method gets called, res is equal 322121535.
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
// Return the number of rows in the section.
NSUInteger res = 0;
if ( state == GRKDemoPhotosListStateAllPhotosGrabbed && section == _lastLoadedPageIndex ) {
NSUInteger photosCount = [_album count];
// Number of cells with kNumberOfPhotosPerCell photos
NSUInteger numberOfCompleteCell = (photosCount - section*kNumberOfRowsPerSection*kNumberOfPhotosPerCell) / kNumberOfPhotosPerCell;
// The last cell can contain less than kNumberOfPhotosPerCell photos
NSUInteger thereIsALastCellWithLessThenFourPhotos = (photosCount % kNumberOfPhotosPerCell)?1:0;
// always add an extra cell
res = numberOfCompleteCell + thereIsALastCellWithLessThenFourPhotos +1 ;
} else if ( section > _lastLoadedPageIndex) {
// extra cell
res = 1;
} else res = kNumberOfRowsPerSection;
return res;
}
I'm the developer of GrabKit. Thanks for using it :)
Actually, the controllers in GrabKit are there for demonstration purpose only, they are not designed to be used "as is" in a project, and more specifically : The GRKDemoPhotosList controller was not made to have another controller pushed in the controllers hierarchy.
So what you need is just a little fix to make grabKit demo's controllers fit to your project :)
I guess the problem is the following :
_ in [GRKDemoPhotosList viewWillAppear], the method fillAlbumWithMorePhotos is called.
_ when you pop back from your controller to GRKDemoPhotosList, this method is called one more time, and it generates this bug.
Try to add a flag in the viewWillAppear method, to avoid calling fillAlbumWithMorePhotos twice, I guess it'll work fine.
Feel free to contact me by mail ( pierre.olivier.simonard at gmail.com ) or on twitter ( #pierrotsmnrd ) if you need more informations or help :)
I'm currently working on an app that populates a UITableView with items from a MPMediaItemCollection. I'm trying to add a UITableViewCellAccessoryCheckmark to the row that matches the title of the currently playing track.
I've done so by creating a mutable array of the track titles, which are also set for my cell's textLabel.text property. (for comparison purposes)
Note: This is all done in - (UITableViewCell *) tableView: (UITableView *) tableView cellForRowAtIndexPath: (NSIndexPath *) indexPath
MPMediaItem *mediaItem = (MPMediaItem *)[collectionMutableCopy objectAtIndex: row];
if (mediaItem) {
cell.textLabel.text = [mediaItem valueForProperty:MPMediaItemPropertyTitle];
}
[mutArray insertObject:cell.textLabel.text atIndex:indexPath.row];
To the best of my knowledge this all works fine except for the below. At this point, I am trying to get the index of the currently playing tracks title and add the UITableViewCellAccessoryCheckmark to that row.
if (indexPath.row == [mutArray indexOfObjectIdenticalTo:[mainViewController.musicPlayer.nowPlayingItem valueForProperty:MPMediaItemPropertyTitle]]) {
cell.accessoryType = UITableViewCellAccessoryCheckmark;
}
Getting to my question, I added all of the above (mostly irrelevant) code because I'm stumped on where I went wrong. When I log indexOfObjectIdenticalTo: it spits out "2147483647" every time, even though there are never more than 5 objects in the array. But why?
If anyone has any tips or pointers to help me fix this it would be greatly appreciated!
2147483647 just mean the object is not found.
From the documentation of -[NSArray indexOfObjectIdenticalTo:]:
Return Value
The lowest index whose corresponding array value is identical to anObject. If none of the objects in the array is identical to anObject, returns NSNotFound.
and NSNotFound is defined as:
enum {
NSNotFound = NSIntegerMax
};
and 2147483647 = 0x7fffffff is the maximum integer on 32-bit iOS.
Please note that even if two NSString have the same content, they may not be the identical object. Two objects are identical if they share the same location, e.g.
NSString* a = #"foo";
NSString* b = a;
NSString* c = [a copy];
assert([a isEqual:b]); // a and b are equal.
assert([a isEqual:c]); // a and c are equal.
assert(a == b); // a and b are identical.
assert(a != c); // a and c are *not* identical.
I believe you just want equality test instead of identity test, i.e.
if (indexPath.row == [mutArray indexOfObject:[....]]) {
Looking at the docs for NSArray
Return Value
The lowest index whose corresponding array value is identical to anObject. If none of the objects in the array is identical to anObject, returns NSNotFound.
So you should probably do a check
NSInteger index = [array indexOfObjectIdenticalTo:otherObject];
if (NSNotFound == index) {
// ... handle not being in array
} else {
// ... do your normal stuff
}
I'm trying to validate dynamically created text fields. The total number of textfields may vary.
The idea is to populate the empty fields with string like player 1, player 2 etc.. Here is what I try
-(IBAction)validateTextFields:sender
{
self.howManyPlayers = 3;
int emptyFieldCounter = 1;
NSMutableArray *playersNames = [NSMutableArray arrayWithCapacity:self.howManyPlayers];
while (self.howManyPlayers > 1)
{
self.howManyPlayers--;
UITextField *tmp = (UITextField *) [self.view viewWithTag:self.howManyPlayers];
if (tmp.text == nil)
{
[tmp setText:[NSString stringWithFormat:#"Player %d", emptyFieldCounter]];
emptyFieldCounter++;
}
[playersNames addObject:tmp.text];
}
}
The problems is that if I touch the button which invoke validateTextFields method. The first and the second textfield are populated with text Player 1 and Player 2, but the third field is not populated.
I notice also that if I type a text let's say in the second field touch the button then remove the text and again touch the button that field is not populated with text Player X.
How to make all that things to work correctly ?
change your code for two lines like this:
while (self.howManyPlayers >= 1) //edited line
{
UITextField *tmp = (UITextField *) [self.view viewWithTag:self.howManyPlayers];
if (tmp.text == nil)
{
[tmp setText:[NSString stringWithFormat:#"Player %d", emptyFieldCounter]];
emptyFieldCounter++;
}
[playersNames addObject:tmp.text];
self.howManyPlayers--; // moved line
}
I forgot ur second question, so edited my answer.
For that try with this. Change if (tmp.text == nil) with if (tmp.text == nil || [tmp.txt isEqualToString:#""])
The reason only two fields are populated is that you are only going through the while loop twice. It should be
while (self.howManyPlayers >= 1)
You should also move the decrement to the end of your while loop
while (self.howManyPlayers >= 1)
{
// other code here
self.howManyPlayers--;
}
For the second part of your question, I think when you delete the text from the control, it stops being nil and now becomes an empty string. So you need to check for an empty string as well as nil in your code.
if (tmp.text == nil || [tmp.txt isEqualToString:#""])