I am looking to use the Parse PFQueryTableViewController to display a list of items stored in cloud.
However, when there are no items, I am looking to show a default Message in the tableview via a customized tableview cell that says "No Item Found".
I am looking for inputs on how customize the PFQueryTableViewController to achieve this.
Thanks in advance
It's doable with some additional method overriding and a little trickery. I would add that (imo) we're straying into territory where the net benefit of the parse.com specialization of the iOS class is reduced.
// lie about the actual count
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
if (self.objects.count) return [super tableView:tableView numberOfRowsInSection:section];
return 1;
}
// answer a dummy object when there are none
- (PFObject *)objectAtIndexPath:(NSIndexPath *)indexPath {
if (self.objects.count) return [super objectAtIndexPath:indexPath];
return [PFObject objectWithClassName:[self parseClassName]];
}
// change how we behave for the dummy object
- (PFUI_NULLABLE PFTableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath object:(PFUI_NULLABLE PFObject *)object {
// check for your dummy object (it will be the only one with no id
// return a special cell in that case
if (!object.objectId) {
// create and return the special custom cell here
// if you're unsure about this, [see this SO answer][1]
} else {
PFTableViewCell *cell;
// the regular cellForRowAtIndexPath behavior goes here
return cell;
}
}
In terms of cost-benefit of the specialized subclass, I feel the same way even about UITableViewController. The most control (and not that much extra work) can be had with a regular UIViewController containing a table view.
Related
I have a layout in which I will have 2 UITableViews with custom cells. The second UITableView must be inside the first.
My question is: how to delegate second UITableView?
Can I delegate both to my ViewController? In that case it will use the same methods and I have to find out which UITableView is managed right now.
Or I have to delegate it inside custom UITableViewCell of the first UITableView?
Any recommendations are appreciated.
EDIT: I don't know how to implement solutions here, because I have Storyboard. Inside my current UIViewController I set delegate and dataSource of the first UITableView to my View Controller.
My problem is that I don't know how to set the same properties of the second Table View (which will be inside UITableViewCell). I can not set them to UITableViewCell (IB does not allow that).
Where and how to set then in the IB?
A far better solution would be to abstract the DataSource and Delegate implementations away from your view controller so that they can be personalised per tableview as required (please note that the code is taken from the objc.io article Lighter View Controllers.
E.g.
#implementation ArrayDataSource
- (id)itemAtIndexPath:(NSIndexPath*)indexPath {
return items[(NSUInteger)indexPath.row];
}
- (NSInteger)tableView:(UITableView*)tableView
numberOfRowsInSection:(NSInteger)section {
return items.count;
}
- (UITableViewCell*)tableView:(UITableView*)tableView
cellForRowAtIndexPath:(NSIndexPath*)indexPath {
id cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier
forIndexPath:indexPath];
id item = [self itemAtIndexPath:indexPath];
configureCellBlock(cell,item);
return cell;
}
#end
Then you could utilise it as follows:
void (^configureCell)(PhotoCell*, Photo*) = ^(PhotoCell* cell, Photo* photo) {
cell.label.text = photo.name;
};
photosArrayDataSource = [[ArrayDataSource alloc] initWithItems:photos
cellIdentifier:PhotoCellIdentifier
configureCellBlock:configureCell];
self.tableView.dataSource = photosArrayDataSource;
The same process could be followed with the UITableViewDelegate implementations to provide you with a very clean, separated and de-coupled code base. Your requirement for two tableviews will then be intrinsically easier to implement.
My answer is
For identifying two table view data source and delegate method is,better to set tag for the table views.
Set this below coding in your tableview delegates method.
if(tableView.tag==0)
{
}
else
{
}
Also you can vary this by assigning different name to these table view.
if(tableView==FirstTableView)
{
}
else
{
}
You just check table condition for every delegate method
Use this code to register custom cell.
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
if(tableView == self.yourFirstTable)
{
CustomCell *cell=[tableView dequeueReusableCellWithIdentifier:#"cellModifier"];
// your code
}
else
{
// second table cell code
}
return cell;
}
-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
if(tableView == self.yourFirstTable)
{
// first tableView number of row return
}
else
{
// second table number of row return
}
}
And create prototype cell in TableView
And Set CellReusableId like this way
I have a UITableView called UserProductViewController and this table view used for two purpose "create and edit" some data. When user click "edit button" open this UserProductViewController edit mode and populate some data within cell from another method. I don't want to store all server-side values in property instead I was use Lazy instantiation cell. This approach sometimes makes trouble. To be clear here is my code this approach correct or not ? Could you please guide me correct way to do this?
Implementation Interface
#interface UserProductViewController()
#property(strong, nonatomic) MyCustomTableViewCell *myCustomCell;
#end
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
...
if(indexPath.row == 2) return self.myCustomCell;
...
}
- (MyCustomTableViewCell *)myCustomCell {
if(!_myCustomCell) {
_myCustomCell = [self.tabView dequeueReusableCellWithIdentifier:#"CustomIdentifier" forIndexPath:[self customIndexPath]];
}
return _myCustomCell;
}
- (NSIndexPath *)customIndexPath {
// 2 correspond to cellForRowAtIndexPath indexPath value.
return [NSIndexPath indexPathForRow:2 inSection:0];
}
Server side method I'm using that cell as a property like this:
- (void) getUserValues {
....
// getting server-side result
// completion block
self.myCustomCell.titleLabel = result.title;
}
Other question is what would happen if I don't want to use tableview dequeue system ?
I'm really new to Objective-C here so what I'm asking may be trivial to most of you but any guidance will help.
Here's a picture of my storyboad.
My current objective is to allow for the user to enter in the number of sets (NSInteger *numReps) and then press the "Log Reps" button and have the table initialize with numReps cells that look like the prototype cell.
Now where I'm at a loss for the implementation. I've never done this kind of thing before so I'm not exactly sure what the best way to go about it is. I have thought of making a custom class for the UITableView table that would take info from the view after the Log Reps button is pushed. I'm not entirely sure how this would need to be implemented. Or can I simply add the table to the properties of the view controller and setup the table within the view controller? That was my initial idea and seems ideal so that I would have everything in one place.
Pleas advise. I am new to all of this and come from a C++ background so I'm still learning a lot of the notation.
Try this:
-(IBAction)btnLogClicked {
int iSet = 4 //Number of row in table
UITableView *tblView= [[UITab;eView alloc]initWithFrame:CGRectMake(0,50,320,100)];
tblView.delegate = self;
tblView.dataSource = self;
[self.view addSubView:tblView];
}
Table View Data Source and Delegate Methods
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return iSet;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}
// Display what you want to display in each cell
return cell;
}
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
[tableView deselectRowAtIndexPath:indexPath animated:YES];
}
It's not clear what you want to present in your prototype cells, but you need an array (or probably an array of dictionaries) to populate the cells. The number of rows is determined by the number of entires (the count) of that array. So, if you take the number entered by the user, and add that many object to your array, then call reloadData on the table, you will get the number of rows that you want. What those object are that you add to the array, depends on what you're trying to show there.
you could start reading: Table View Programming Guide for iOS
But I can answer you:
You can add the UITableView to the UIViewController, but you need set your UIViewController like the TableView's delegate and dataSource. Your ViewController need to implement the protocol: UITableViewDataSource
The method that you are looking for is: tableView:numberOfRowsInSection:
But I really recommend you that read the Apple Reference.
I have three UITableView's and they all need access to essentially the same data. The only difference is how each table view formats the data. What is the best way to implement this? I was thinking that if each table view had a tag of some sort, I could reference that from my data source when sending back the UITableViewCell's.
Each of the datasource calls passes in the UITableView that is requesting the information. Comparing this tableview to your three, you can determine which one it is and format the data differently. I would probably implement separate methods for each tableview and, pass the datasource method to the appropriate method. The other method would then create the customized cell creation and setup. eg for cellForRowAtIndexPath:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
if (tableView == [self tableView1])
return [self tableView1:tableView cellForRowAtIndexPath:indexPath];
if (tableView == [self tableView2])
return [self tableView2:tableView cellForRowAtIndexPath:indexPath];
if (tableView == [self tableView3])
return [self tableView3:tableView cellForRowAtIndexPath:indexPath];
Assert0(NO, #"UITableView not recognized!");
return nil;
}
- (UITableViewCell *)tableView2:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
// Do normal cell creation for tableView1 here
}
I don't know if there's any gotchas off-hand for running multiple UITableViews off of the same datasource, so tread lightly.
look into singleton design pattern - here is an example on how to implement for iOS.
The code below is creating a search for many strings. Initially there are 5 rows, when you reach row five, it adds another row. Instead of just directly editing the row, i load a filter controller (another view controller that as you type it completes words for you). When the user finishes finding a word he clicks it and comes back to this view controller. Now i want to fill the cell that was originally tapped with the text from the filter.
I tried asking earlier and didn't get any concrete answers.
I am running into a problem where when i scroll (after adding a new row), it starts filling in those rows with info already in the table, (as opposed to staying blank)
Please help me where i am going wrong
//global indexpath to remember which cell tapped
NSIndexPath *globalPath;
#interface SearchViewController ()
#end
#implementation SearchViewController
//Load implementation once per launch
- (void)viewDidLoad
{
[super viewDidLoad];
[self linkInputTableToDelegate];
_temporaryResultsArray =[[NSMutableArray alloc]init];
_flurryArray=[[NSMutableArray alloc]init];
_numberOfSections=6;
}
-(void)viewWillAppear:(BOOL)animated{
[super viewWillAppear:NO];
[InputTable reloadData];
textFromUserDefaults=[[[HelperMethods alloc]init]getObjectUserDefault:#"textFiltered"];
[self addTextToFlurryArrayForFlurryAndSavedLists:_textFromUserDefaults];
}
-(void)viewDidDisappear:(BOOL)animated{
}
- (IBAction)searchButtonPressed:(UIButton *)sender {
self.tabBarController.selectedIndex = 1;
}
//Makes the input table respond to delegate table view methods
-(void)linkInputTableToDelegate{
_inputTable.dataSource=self;
_inputTable.delegate=self;
}
-(void)performSearch:(NSString*)text{
//do search
}
#pragma mark - Table view data source
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
int numberOfRows=_numberOfSections;
//Rows for iPhone 4
if ([[UIScreen mainScreen]bounds].size.height==480) {
numberOfRows=numberOfRows;
//Rows for iPhone 5
}else if ([[UIScreen mainScreen]bounds].size.height==568){
numberOfRows=numberOfRows+1;
}
return numberOfRows;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
//In reality groups are created with 1 row inside, this is to allow spacing between the rows
return 1;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *kCellID = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:kCellID];
if (!cell) {
cell = [[UITableViewCell alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:kCellID];
}
//Is the cell the same as the one clicked when going to ingredient filter
BOOL cellIndexPathSameAsSelected=[self isCellIndexSameAsPreviousClicked:indexPath];
cell.textLabel.textColor=[UIColor blackColor];
if (cellIndexPathSameAsSelected && _textFromUserDefaults!=nil) {
if (![cell.textLabel.text isEqualToString:_textFromUserDefaults]) {
cell.textLabel.text=_textFromUserDefaults;
[self performTextSearch:_textFromUserDefaults];
}
}
return cell;
}
//Compares the previous clicked cell with the cell now selected
-(BOOL)isCellIndexSameAsPreviousClicked: (NSIndexPath*)cellPath{
if (cellPath.row == globalPath.row && globalPath.section==cellPath.section) {
return YES;
}
else{
return NO;
}
}
- (void)updateTableViewWithExtraRow :(NSIndexPath*)rowSelected{
NSLog(#"number of sections =%i",_numberOfSections);
if (rowSelected.section == _numberOfSections) {
_numberOfSections ++;
}
}
#pragma mark - Table view delegate
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
NSString *cellText = [tableView cellForRowAtIndexPath:indexPath].textLabel.text;
[[[HelperMethods alloc]init]saveObjectToUserDefaults:cellText :#"textFiltered"];
globalPath = indexPath;
[self updateTableViewWithExtraRow:indexPath];
}
-(void)addTextToFlurryArrayForFlurryAndSavedLists:(NSString*)text{
if ([_flurryArray count]==0 &&[text length]>0) {
[_flurryArray addObject:text];
}
for (int i=0;i<[_flurryArray count];i++) {
NSString *textInArray=[_flurryArray objectAtIndex:i];
if (![textInArray isEqualToString:text]) {
[_flurryArray addObject:text];
}
}
NSLog(#"Total number of saved items = %i",[_flurryArray count]);
}
// Dispose of any resources that can be recreated.
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
}
I have a couple of reactions looking at the code:
A couple of observations about the proper use of the UITableViewDataSource methods, specifically numberOfRowsInSection, numberOfSectionsInTableView, and cellForRowAtIndexPath:
These really should be driven by some model data structure (e.g. a NSMutableArray) and nothing else;
These methods should be stateless. They should not relying on the value of some NSString instance variable, like _textFromUserDefaults) but rather always look up the value in the NSMutableArray model structure on the basis of the value of the indexPath parameter. You simply cannot make any assumptions about when cellForRowAtIndexPath will be called. This may well account for your duplicate values.
None of these should be doing anything besides responding to the UITableView inquiry. For example, your cellForRowAtIndexPath is invoking performTextSearch. It really shouldn't do anything except return the cell.
Your cellForRowAtIndexPath currently has conditional logic and only updates the cell if certain conditions holds. Because cells are reused, you really want to make sure that you initialize the cells regardless. You can't be assured that the cell is blank when you get it, nor that the previous contents are the previous values for that indexPath. Because cells are reused, it could be for an entirely different row. This could also account for your duplicative entries.
Regarding the interaction of the master view controller and the details view controller, there are more elegant ways than passing data back and forth via NSUserDefaults. For example when you initiate the details view controller, you could just pass it the information it needs. And when it's done, it should call a method in the master view controller to update the data in the master view. To do that, the master view controller should conform to some protocol of your own creation. If you see the example I shared via chat, you can see what that might look like. Anyway, by having some delegate method in the master view controller that the detail view controller calls when it's done, that eliminates the rather fragile technique of using viewDidAppear to control the updating of the master table view.
You might want to contemplate employing "edit" (which allows you to delete, possibly also edit a particular row) and "add" buttons like the standard "master-detail" template that Xcode provides. There are a number of standard conventions here that might be better than having an array of blank cells that you can then tap on. Clearly, your user experience is entirely up to you, but you can always contemplate whether there are existing, familiar conventions that you might employ.
Rob's feedback is good. In broader terms, you can't rely on the cells in a UITableView to hold onto their data. For efficiency, it will be creating, using, and destroying cells at will, and using cellForRowAtIndexPath to figure out what they should look like. Instead of testing what's in a cell, you need to have your own set of data which describe the value of each cell, and just set the value based on the indexPath. I'd recommend storing all your cell information in an NSMutableArray which contains NSStrings or something more complicated if necessary. It will be easy to set default values when you add cells to the array. Then cellForRowAtIndexPath can just access the array rather than attempting its own logic based on current cells.