NSFetchedResultsController predicate to eliminate duplicates of several properties

The name of the pictureThe name of the pictureThe name of the pictureClash Royale CLAN TAG#URR8PPP



NSFetchedResultsController predicate to eliminate duplicates of several properties



I am using an NSFetchedResultsController in my UITableViewController.



Is it possible to specify a predicate that will not retrieve items which have duplicate fields in x number of fields that I specify.



For example, I want to search all results for items but if the itemName AND itemDescription AND itemQuantity are the same, I want only one of these items.




1 Answer
1



When the page loads do a single run through the data and keep a list of objectID that are duplicate. For duplicate object set the row height of the cell to be 0. So they are technically still there, but you can't see it. This make dealing with the NSFetchedResultsControllerDelegate calls easy because no indexPaths have changed



If the dataset is always selected in the same way and an object that is a duplicate is always a duplicate you can set an 'isDuplicate' in the object and filter it out in the predicate. Or you can not store at all in the first place. If objects are displayed in different sets and in different way and sometime should be displayed and sometime not be displayed this is not a good solution



If you are sorting by the same criteria that make an object duplicate (that is duplicates always appear right next to a non-duplicate) and you are NOT using sections, then you can use sectionKeyPath. SectionKeyPath groups items together into sections. Group the duplicate and non duplicate together and then display every section as a single row (use the first item in each section). The indexPaths of the fetchedResultsController will not match the indexPaths of the tableview so you have to careful to convert them.



Instead of accessing the objects from a fetchedResultsController do a fetch and and filter the array. Then use the array to display the objects. The downside is that you don't get updates on when objects change. This can be especially problematic is objects are deleted, as accessing a managedObject that's entity was delete can lead to a crash.



I recommend option 1






By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.

-

Popular posts from this blog

Firebase Auth - with Email and Password - Check user already registered

Image
Clash Royale CLAN TAG #URR8PPP Firebase Auth - with Email and Password - Check user already registered I want to check when a user attempts to signup with createUserWithEmailAndPassword() in Firebase user Authentication method, this user is already registered with my app. createUserWithEmailAndPassword() 8 Answers 8 To detect whether a user with that email address already exists, you can detect when the call to createUserWithEmailAndPassword () fails with auth/email-already-in-use . I see that @Srinivasan just posted an answer for this. createUserWithEmailAndPassword () auth/email-already-in-use Alternatively, you can detect that an email address is already used by calling fetchSignInMethodsForEmail() (previous called fetchProvidersForEmail() ). fetchSignInMethodsForEmail() fetchProvidersForEmail() When the user trying to create an user with same email address, the task response will be "Response: The email address is already in use by another account." mFirebas
Read more

Dynamically update html content plain JS

Image
Clash Royale CLAN TAG #URR8PPP Dynamically update html content plain JS So I have a script bound in my index.html, which literally has to fetch an array of jsons from an api, then dynamically update my page when get response. But as a result I'm getting an as the only update of my page. here is my script fetch(url) .then((resp) => resp.json()) .then((resp) => resp.results.forEach(item => fetch(item.url) .then((response)=> response.json()) .then((response) => pokeArr.push(response)) .catch(console.log) ) ).catch(console.log) const filler = () => if(!pokeArr) return 0 pokeArr.map((i,j)=> return `<tr>$i.name</tr>` ) const pokeindex = () => document.getElementById('a').appendChild(document.createElement(filler())) pokeindex() When I'm consoling it, I can see in the console all the responses I get, so I'm at least doing the fetching part right. What's parberakan ? What's pokeArr ? – T.J. Crowder Aug 8 at 12
Read more

How to determine optimal route across keyboard

Image
Clash Royale CLAN TAG #URR8PPP How to determine optimal route across keyboard I'm trying to automate the typing process in a video game. Players are given an on-screen QWERTY keyboard layout that they can navigate with the control stick (up, down, left, right) in order to select a letter to type. I was wondering if there was a module for Python (or some other resource I could explore) that would help my program find a path across the keyboard as it types each letter in a given message. In other words, if the first letter typed was "A" and the next letter was "B", the module would know that the program should move 1 space down on the keyboard and 4 spaces to the right. Currently, I have the program resetting to the "G" key after each letter is typed (allowing me to use fixed-directions as the program parses each character in the desired message). As you can imagine, this is quite inefficient and defeats the purpose of automating the typing in the fir
Read more