I have a view which shows a list of entries in a UITableView. The data for the list is an NSArray. When the user is on this view, there is an asynchronous call to a webservice to retrieve the latest entries. When I have downloaded the latest entries, I update the NSArray and then I send off a notification to the notification center. The UITableView is listening to this event and will try to reload the table.
But with this approach I get an error which is on the lines of "The object was mutated during reading".
After going through similar questions here on SO, I see the suggested approach is to remove objects and add objects at individual indexes and ask the table view to reload the data.
Is there a way to replace the array completely and ask the table view to reload the data ?
UITableView's reloadData method should do the trick.
From Apple's documentation:
Call this method to reload all the data that is used to construct the
table, including cells, section headers and footers, index arrays, and
so on. For efficiency, the table view redisplays only those rows that
are visible. It adjusts offsets if the table shrinks as a result of
the reload. The table view's delegate or data source calls this
method when it wants the table view to completely reload its data. It
should not be called in the methods that insert or delete rows,
especially within an animation block implemented with calls to
beginUpdates and endUpdates
https://developer.apple.com/library/prerelease/ios/documentation/UIKit/Reference/UITableView_Class/index.html#//apple_ref/occ/instm/UITableView/reloadData
if you have Updated NSArray Object
Then you can use directly following method of UITableView
[tableView reloadData]
Related
I am using a FetchedResultsController to fetch the data for my UITableView. The data is created via actions performed on another tab (so my table may have 5 items but if I switched tabs and go back to my table, it may have more than 5 items that it should display). My table can potentially contain many rows. Right now I am using [myFetchedResultsController performFetch] in my viewDidLoad.It appears that when I create data in my other tab, when I switch back to my table tab, that new data is put into my table automatically without me perfomring [myFetchedResultsController performFetch] again. Here are my questions:
1) Does a fetchedResultsController automatically monitor the manajedObjectContext for changes and fetches the new objects if they come into existence? (This appears to be what is happening but I just want to make sure. Perhaps I have some code that is helping me do this that I forgot I put in somewhere)
2) Does the fetch performed by [myFetchedResultsController performFetch] fetch all of the objects at that time, or does it fetch only what it can fit in the view of the table and it fetches the rest later as it needs it (as you scroll in the table)? I ask because since my table can potentially have a lot of rows, it seems inefficient to fetch all the data at once if only ~12 of them will be displayed on the table at once.
EDIT: I just realized that in my FetchedResultsController delegate methods, I have
- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller
{
[self.tableView reloadData];
}
Am I correct in saying that a fetchedResultsController monitors for change, but will not apply it to the table unless the table is reloaded as I have done? If so, then I have another question about UITableView. Does reloading the table only reload the rows in view and then the other rows are updated as you scroll? Again I ask because if my data is very large, it seems inefficient to reload the entire table if it will reload all rows at once.
Yes, if you add a delegate
You should set the fetch request batch size when you configure the FRC because it can only load an appropriate number of items for the screen if you tell it how many that is.
You apply the changes, the FRC just collects and supplies the data. The delegate method tells you about a change. Reloading affects the whole table in terms of row count but only shows the visible rows (assuming the batch size is set appropriately).
I want to create one application that read many data from json and show them in tableview.
I want to create one button that when to click on it this page for a second time to be refresh and take data from json (check json again and if this json changed tableview also changed)
I dont know how create this function that refresh this page and run code at first.
please tell me about it.
[self.tableView reloadData]
to load more data from webserver in to table
Put a button in header of section. I think that is the best place. In target method of that button call json and download all data. then call [self.tableView reloadData]. It will call all table methods like number of row , sections, cellForRow.
Why don't you use the Default RefreshControl provided in iPhoneSDK.
A UIRefreshControl object provides a standard control that can be used to initiate the refreshing of a table view’s contents. You link a refresh control to a table through an associated table view controller object. The table view controller handles the work of adding the control to the table’s visual appearance and managing the display of that control in response to appropriate user gestures.
Check this to learn about its implementation : Working with UIRefreshControl
You can place a UIToolBar above the tableview. In that you can have a barbutton, to which you could give an action to fetch the data again. Once the data fetch is done, call
[self.tableview reloadData];
I've a UITableViewDataSource which maintains sections of data items which will be presented by an UITableView instance. The table view is editable, allowing insertion and deletion of rows and sections, and all changes on the view should be written back to the data source. After reading through the Apple documents, I can deal with insertion and deletion on rows by sending message tableView:commitEditingStyle:forRowAtIndexPath: to the data source.
But, however, I can't figure out what is the standard way to feedback the changes on sections to the data source. Please kindly help.
The delegate method tableView:commitEditingStyle:forRowAtIndexPath: is called by the table view to tell you what the user has done (what they have added / removed). It is then the responsibility of your code to make the appropriate changes to your Model and reload the table view.
The simplest way to reload is to call reloadData, and you also have more specific options for reloading / inserting / removing individual rows or sections - this is all from a UI perspective and the table view requires that you have updated your Model before you call any of these methods or the table view will throw an exception.
I want to edit UITableView by calling EditTable method on a button click of some other class. In other words, I want to delete rows from UITableview from some other viewcontroller without navigating to that UITableView.
Please tell me the way to achieve this or any sample code for it.
If you want to delete rows from a tableview you just need to delete the corresponding rows from the datasource. When the table is next shown it should know how to reload it's data so the changes in the datasource are applied to the table.
Edit
You shouldn't rely on sending messages to view controllers that are deeper in the stack because they may have been unloaded already.
In my application, I have a UITableView with a few rows (let's call it TV1), now, at the bottom of these rows is a row that drills down into another (TV2). This new TV2 asks you which type of data you would like to add to the first view. Then, when the user selects which kind, they're brought to another view, in which they fill in some fields, the data is saved, and they're sent back to TV1, however, the data they entered, isn't loaded and I'm not really sure how to do this. Any ideas?
Maybe you did this already, but how about using [TV1 reloadData];? This forces the entire table to reload, yet there are also more specific methods for reloading just the cells that have been altered. See also the documentation: UITableView
Reload your table view by calling [self.tableView reloadData] in the viewcontroller's viewWillAppear: method. It will be called when the user switches back to your view. Right before it is actually put on screen.