I have the following header file
#interface Menu : UITableViewController;
and the following m file
#import "Menu.h"
#implementation Menu
+ (void)initialize {
// TODO here I want to add cells to my table view
}
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)newIndexPath{
[tableView deselectRowAtIndexPath:newIndexPath animated:YES];
//my logic goes here
}
#end
I want to be able to add cells to my tableview in initialize method, how can I do that ??
To add cells to you table, you must implement the delegate and data source methods.
- tableView:cellForRowAtIndexPath: Will create and return a cell for the specified index path, which itself is basically a section and row number.
- tableView:numberOfRowsInSection: Specifies the number of cells to be in the table.
You can see the documentation here.
There is a good tutorial here.
Related
i am new to iOS, this may seem like a basic question. I have been working through this tutorial and I have no idea how the tableview is connected to the code. The sample project can be downloaded here.
I was my understanding that you need to extend UITableViewDelegate, UITableViewDataSource in the code, then in the storyboard you can drag from the tableview to them.
But what is perplexing is that the sample project does not extend UITableViewDelegate, UITableViewDataSource at all, therefore, how is the tableview in the story board connected to the code ?
Datasource is used to supply data and delegate is used to supply behaviour. UITableView asks your datasource every time it needs data to display. It provides a lot of flexibility for how you choose to represent your underlying data model. You simply define specific methods to use in order to get table information, and iOS can call them when it needs to know something like the number of rows in a section, or the content of a particular row.
You will probably implement your own delegate mechanism in the future. It is a great design pattern which handles interaction/data transfer between objects.
Because, the basic class adopts from UITableViewController
#interface WTTableViewController : UITableViewController
In your storyboard you just ctrl-drag from tableview to viewController and choose delegate and dataSource.
https://developer.apple.com/library/ios/documentation/UIKit/Reference/UITableViewDataSource_Protocol/ you should refer this it will help u alot
If you working with TableViewController, UITableViewDelegate and UITableViewDataSource are connected to table automatically. In case you are working with ViewControler which contains TableView, you have to add UITableViewDelegate and UITableViewDataSource like this: #interface myViewController : UIViewController <UITableViewDelegate, UITableViewDataSource>. In new versions of Xcode you can drag delegate and data source to table, and if you want to set delegate programmatically, you can add this two lines of codes:
[tableView setDelegate:self];
[tableView setDataSource:self];
or, equally:
tableview.delegate = self;
tableview.dataSource = self;
In viewcontroller.h file e
declare the delegate and datasource method.
UIViewController<UITableViewDataSource,UITableViewDelegate>
then
connect the delegate and datasource method with viewController so
in viewController.m file
- (void)viewDidLoad {
tableview.delegate=self;
tableview.dataSource=self;
}
In Objective-C/iOS you often implement things by having classes conform to protocols rather than subclassing classes. WTTableViewController conforms to the protocols
UITableViewDataSource: https://developer.apple.com/library/ios/documentation/UIKit/Reference/UITableViewDataSource_Protocol/
and
UITableViewDelegate: https://developer.apple.com/library/ios/documentation/UIKit/Reference/UITableViewDelegate_Protocol/
In MainStoryboard.storyboard you can see in the inspector to the right that the TableViewController has a custom class of WTTableViewController
The relevant methods in WTTableViewController.m:
#pragma mark - Table view data source
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return 2;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return 0;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"WeatherCell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];
// Configure the cell...
return cell;
}
#pragma mark - Table view delegate
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
// Navigation logic may go here. Create and push another view controller.
}
Here's some general info about protocols: https://developer.apple.com/library/ios/documentation/Cocoa/Conceptual/ProgrammingWithObjectiveC/WorkingwithProtocols/WorkingwithProtocols.html
I suggest reading a beginners book or tutorial on iOS to pick up the overall design principles otherwise many things can be quite confusing.
using Objective-C
I have a table with cell that can be swiped (as example use this post with some changes in logic). Currently i can swipe cell and after flipping table it's "state" will be reset to "closed". I want to implement some "memory" mechanism for storing last state of each cell.
How I try to do it - in cell class create protocol, where implement 2 methods for getting current indexPath of cell and adding it to the NSMutableSet, and before presenting it, controller check if this cell already in collection - set required state.
I use separate .xib files for both viewController with tableView and tableViewCell.
Code - cell.h class file:
#protocol PEDoctorsViewTableViewCellDelegate
#optional
//buttonAction
- (void)buttonDeleteAction;
//method for closing cell with swipe
- (void)cellDidSwipedIn: (UITableViewCell*)cell;
//method for opening cell with swipe
- (void)cellDidSwipedOut:(UITableViewCell *)cell;
#end
#interface PEDoctorsViewTableViewCell : UITableViewCell <PEDoctorsViewTableViewCellDelegate>
#property (strong, nonatomic) id <PEDoctorsViewTableViewCellDelegate> delegate;
//method for protocol PEDoctorsViewTableViewCellDelegate
- (void)setCellSwiped;
#end
cell.m file
...
//add some code for handling reuse of cells
//fixing issue with not remembeering of cell's state
//close all cells during flipping tableView
- (void)prepareForReuse{
[super prepareForReuse];
//close all cells before showing
self.viewDoctorsNameView.frame = CGRectMake(0, 0, self.viewDoctorsNameView.frame.size.width, self.viewDoctorsNameView.frame.size.height);
}
And viewController with tableView class.m
#pragma mark - PEDoctorsViewTableViewCellDelegate
- (void)cellDidSwipedOut:(UITableViewCell *)cell{
NSIndexPath * currentOpenedCellIndexPath = [self.tableView indexPathForCell:cell];
[self.currentlySwipedAndOpenesCells addObject:currentOpenedCellIndexPath];
}
- (void)cellDidSwipedIn:(UITableViewCell *)cell{
[self.currentlySwipedAndOpenesCells removeObject:[self.tableView indexPathForCell:cell]];
}
- (void)buttonDeleteAction {
NSLog(#"delete action");
}
and check in - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath method like
if ([self.currentlySwipedAndOpenesCells containsObject:[self.tableView indexPathForCell:cell]]){
[cell setCellSwiped];
}
also this class have
//place to store set of opened cells
#property (strong, nonatomic) NSMutableSet * currentlySwipedAndOpenesCells;
initialized in - (void)viewDidLoad.
As result - i got all cells with reset position.
I try to change code in - (void)prepareForReuse method - position of cell changes according to my changes in method - this part works fine.
Try to check delegate method - all fire in exactly required moment.
Try to add some NSLog method before adding object in NSMuatbaleSet and before cell will be recreated (think maybe data lost) - result - during adding object in to set - all looks like OK:
During recreating - looks like OK too :
but not changes in table shown. I try to check what object are captured during saving -
and after small flip for starting recreating process got next:
as I understand - same cell now a new object. Also try to add some BOOL property to cell for controlling and comparing it's state - result the same - each time new cell.
Any idea what i'm doing wrong?
I would like to call a method when a UITableViewCell is selected/tapped. I could do it easily with a static table view, but it requires a UITableViewController which is not good for me in this case, therefore I'm using a normal vc.
I have 10 specified methods like this:
- (void) methodOne {
NSLog(#"Do something");
}
- (void) methodTwo {
NSLog(#"Do something");
}
....
And I would like to call the methodOne when the first cell was tapped, call the methodTwo when the second cell was tapped and so on..
As a first step I set the numberOfRowsInSection to return 10 cells, but have no idea how could I connect the selected cells with the methods. Is there any quick way to do it? It would be a dirty solution to create 10 custom cells and set the every method manually for the custom cells, and there is no free place for it.
You can create an array of NSStrings with method names in the order they should be called from their corresponding UITableViewCells.
NSArray *selStringsArr = #[#"firstMethod", #"secondMethod", #"thirdMethod];
Then create a selector in tableView:didSelectRowAtIndexPath: from the strings array and call it using performSelector:.
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
NSString *selString = selStringsArr[indexPath.row];
SEL selector = NSSelectorFromString(selString);
if ([self respondsToSelector:#selector(selector)]) {
[self performSelector:#selector(selector)];
}
}
Of course, there are some limitations to using performSelector: which you can read here.
You can use this method for whenever any cell is tapped on the table view
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
NSInteger selectedRow = indexPath.row; //this is the number row that was selected
switch (selectedRow)
{
case 0:
[self methodOne];
break;
default:
break;
}
}
Use selectedRow to identify which row number was selected. If the first row was selected, selectedRow will be 0.
Don't forget to set the table view's delegate to your view controller. The view controller also has to conform to the UITableViewDelegate protocol.
#interface YourViewController : UIViewController <UITableViewDelegate, UITableViewDataSource>
As long as the table view has a data source and a delegate, it doesn't matter what kind of view controller it is on. All a UITableViewController really is is a UIViewController that already has a table view on it and is that table view's delegate and data source.
I try to display objects of an array in a tableview.
This is a single screen app, I'm using storyboard.
When running - the tableview appears as an empty grid. the data of the objects is not displayed. what may cause this?
Having 2 required methods numberOfRowsInSection and cellForRowAtIndexPath I suspect the last one.
The .h file contains this row:
#interface MYViewController : UIViewController <UITableViewDataSource, UITableViewDelegate>
I set the delegate & datasource via the code as you suggested. still empty grid.
This is my implementation:
-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { return [listRecipes.recipeArray count]; }
-(UITableViewCell )tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString cellIdentifier = #"ListCellIdentifier"; MYCustomListCell* listCell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier]; NSString* dataString = listRecipes.recipeArray[indexPath.row]; listCell.listName.text = dataString; listCell.imageView.image = [UIImage imageNamed:dataString]; return listCell; }
I try to display data from an array in MVC .
If the array is local - the data is displayed
Can you please advise what to do?
Thank you in advanced.
Always remember to hook up your table's delegate and datasources.
Being a UIElement on a UIViewController that conforms to these two protocols is not enough for Xcode to assume that that UIViewController should be the delegate and/or datasource for the table.
Right click on your tableview, drag from delegate & datasource to your UIViewController.
You can also set these programmatically via:
self.table.datasource = self;
self.table.delegate = self;
And if you're still having trouble after this, you'll have to show us how you're implementing the datasource protocol methods.
Check if your initialisation of tableview delegate and datasource would be before the recipeArray is initialised. In this case you will have to tableView.reload() after the items are added to recipeArray .
I have one parent class with one tableview.
That class is the delegate and datasource of that tableview as well.
Now I subclassed (derived) that class and made a child class.
I have one tableview in child class too.
Then I defined delegate and datasource functions in that child class, but it overrides parent class tableview data source/delegate methods.
But I want both of them to be separate.
However my Requirement is as Follows :
I want to retain a search bar and side button, on the top of all the viewControllers that search bar includes , a recent searches terms table underneath that.
So i thought of defining parent class for that and subclass other viewControllers from that class.
Am i doing it the right way ?
I assume you are talking about a view controller class. If I understood you right, then you are about to mess it up. Delegation is a way to avoid subclassing. Of course you can subclass the delegate - no problem. But you want a table view in the super class that owns a table in its view. And you want a subclass that has another table in its view plus the table that the superclass owns.
That is not impossible. But from your subclass' point of view, your subclass owns two table views. Even that is possible. Your view controller is the delegate of two tables (regardless of where in the view hierarchy they are declared and instanciated). When you now override the delegate and data source methods theny your subclass must either:
Determine which table it is dealing with/being called from. And then serve both tables appropriately.
Determine wich table it is dealing with/being called from. And then serve "its own" table appropriately and calls [super sameMehtod:withSamePamaters] to ensure that the superclas can still provide the data and server as delegate.
Which of both is smarter depends on the context and what you are about to achieve in detail.
A way of determinnig which table's delegate was called can be done by tagging the table views (do not use 0 as tag) or by comparing the tableView parameter of the delegate method with the corresponding properties (IBOutlets in this case). (In other cases you can compare the sender parameter with the IBOutlets. But tagging is probably easier to understand when reading the code later.)
Let's look at an example of the UITableViewDataSourceDelegat:
Your superclass implements:
#interface MySuperTableViewController:UITableViewController <UITableViewDelegate>
// There will be something in here.
// But it inherits self.tableView from UITableViewController anyway. We leave it with that.
#end
#implementation MySuperTableViewController
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
// This method creates or re-uses a cell object and sets its properties accordingly.
}
#end
And your subclass:
#interface MySubTableViewController : MySuperTableViewController // no need to declare the delegate here, it is inherited anyway
#property (weak, nonatomic) IBOutlet UITableView *mySecondTableView; // self.table will be used by the superclass already.
#end
#implementation MySubTableViewController
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
if (tableView == self.table) { // This call refers to the one talbe that is managed by super
return [super tableView:tableView cellForRowAtIndexPath:indexPath];
}
// This method now creates or re-uses a cell object and sets its properties accordingly.
// You may want to check wether tableView == self.mySecondTableView etc.
}
#end
(This comes from scratch, not syntax checked etc. Do not expect this to run properly right away :)
BUT ... please re-consider your class structure. I am afraid you are getting lost in some rather unlogical class hierarchy. There is nothing wrong with having two talbes managed by a common view controller even without this subclassing-thing. And there is nothing wrong with using multiple tables in a view where each of the tables has its own delegate (can be a view controller). Since iOS 5 (or was it introduces with 6) we can use the UIContainerView for that purpose and nicely build it up in IB/storyboard.
try this,
ViewController.h
IBOutlet UITableView *firstTable;
IBOutlet UITableView *secondTable;
ViewController.m
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
// Return the number of sections.
if (tableView == firstTable) {
return 1;
}
else if(tableView == secondTable)
{
return 1;
}
return 0;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
// Return the number of rows in the section.
if (tableView == firstTable) {
return [arrItems count];
} else if(tableView == secondTable)
{
return [arrData count];
}
return 0;
}
etc etc ....