Use Realm data to fill the UITableView (table)? - objective-c

Question

My solution which doesn't work - I get data with realm store it as array and reuse this array in cellForRowAtIndexPath:.
The problem is I should get data in the background thread but fill the table in main thread.
Note: I have already read that if I get the realm data in current thread then I can use them in this thread only. Otherwise I should create ThreadSafeReference for each realm object I need and reuse it in main thread. But I can't understand how to do it - the example is written with such way that they create an object before dispatch_async and use it inside this object (like passing a variable into the code block).
In my case I have a separate array which I should store and reuse in cellForRowAtIndexPath (which is not code block) and called multiple times. I also can't call dispatch_async with a thread I need inside it because the cell may become invalid.
How to solve this issue? Should I cache Realm objects manually? I accept both Swift and Objective-C languages

Answer 1

The following code should work for you:
// ViewController.h
#import <UIKit/UIKit.h>
#import "MyObject.h" // subclass of RLMObject
#interface MyViewController : UIViewController <UITableViewDelegate, UITableViewDataSource>
#property (weak, nonatomic) IBOutlet UITableView *myTableView;
#property RLMResults<MyObject *> *objectsList;
#end
And the implementation:
// ViewController.m
#import "MyViewController.h"
#implementation MyViewController {
- (void)viewDidLoad {
_objectsList = [MyObject allObjects]; // optionally sort, query, etc.
}
- (void)viewDidAppear {
[super viewDidAppear];
// Do any other setup
}
#pragma mark - UITableViewDataSource
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
return _objectsList.count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
// Setup the cell with the object's information. It's up to you how
// to do it. Register a custom subclass of UITableViewCell, for example.
MyObject *thisCellObject = [objectsList objectAtIndex:indexPath.row];
UITableViewCell *cell = [self.myTableView dequeueReusableCellWithIdentifier:#"customIdentifier"];
// Title should be a property on your MyObject class
cell.textLabel.text = thisCellObject.title;
}
#pragma mark - UITableViewDelegate
// Implement the Delegate methods as you want it...
}
No need to invoke the Realm Objects from other threads of using Dispatch. The only case you'll get those "incorrect thread" errors would be if you pass a reference from you view controller to other class, like a background networking client or something similar.
Anyway those cases are avoidable too. If your objects got an ID, let's say from an API, you pass the ID to the other class, maybe the background sync client, and from that client perform a query for the object, like [MyObject objectsWhere:#"objectID == %#", idString];. The object is being called from the background process that will use it and therefore it's not going to fail.