how to avoid duplicate values in core data swift

You could go for an NSOrderedSet but this class does not give you type completion and you’ll have to work with Any instances. Prevent Duplicate Entries. EF Core will view these objects as entirely unrelated to the database. However, I didn't mention relationships in that discussion. Swift + Core Data . I don't see any reason to get duplicated values if your database has correct records. Whenever you update a record, Core Data loads the record into memory, updates the record, and saves the changes to the persistent store, a SQLit… When I do a Batch Update, it just creates new duplicate records instead of overwriting the existing ones as intended.Why oh why? 3.2 Adding the task to Core Data. When you use this last version, you might lose the order of your original array which means you should only use this version if you don't care about the ordering of your array: By converting the array to a Set, all duplicate values are automatically dropped from the array. Removing duplicates to get unique values out of an array can be a common task to perform. By Alan Anderson, David Semmelroth . In the above array, if we go through then it should return project_code : 1 If anyone can write a code in Swift .. If keeping the order is important in your case you might not want to go with a Set. On the Data tab, in the Data Tools group, click Data Validation. Creating NSManagedObject Subclasses. If it matches then its duplicate and if it doesn't, then there are no duplicates. The previous two versions of uniqueElements preserved the ordering of your input. In the table, we have a few duplicate records, and we need to remove them. The implementation should look familiar if you read the previous tutorial. There’s a lot of ways to achieve the same result and each of them has their own pros and cons. With createRecordForEntity(_inManagedObjectContext) im… We can get some type-safety and Swift-only features like enums and optionals. I have to check on some system info and insert data into the database. It’s important to keep performance in mind when creating that extension as we could easily end up with a quadratic time complexity o(N²). How to Deal with Duplicate Values in Your Data; How to Deal with Duplicate Values in Your Data. I know that not every iOS developer has to learn everything on this list. Option 1: Make the Username field as Primary Key/ Unique Key, so the same username data will not be inserted, which in turn throws an exception. We can then convert the set back to an array to get an array with all duplicate values removed. Arrays in Swift can hold on to all kinds of data. Here we need to loop through and find if same project_code and lob is same, then it would return which all project_code which are duplicate. You handle the appropriate exception and intimate the user. Note that I defined a Set in this updated implementation. But Core Data takes it a step further by allowing you to describe how its entities relate to other entities, as well as adding rules for validation and uniqueness. Data is stored in different ways in different systems. It's much better. You'll get thirteen chapters, a Playground and a handful of sample projects to help you get up and running with Combine as soon as possible. Sometimes these configurations can be large and the implications of a configuration change can be far-reaching while other times a configuration Read more…, 10 things iOS developers should focus on in 2021, Building a simple remote configuration loader for your apps. Without going too much into detail on the differences it’s good to know that a Set is not maintaining the order. Swift can bring clarity to our code, thereby making it easier in some ways to use Core Data. Before you can remove defaults from an array, you should consider implementing Equatable for the object you're storing in your array so we can use the == operator to compare them: Once you've determined that you're dealing with Equatable objects, you can define an extension on Array that will help you remove duplicate values as follows: This way of removing duplicates from your array is not very efficient. For the Point struct I showed you earlier this is easy to achieve. Feel free to contact me or tweet to me on Twitter if you have any additional tips or feedback. Custom debug descriptions can help you debug your own custom objects, structs, errors, and other types. Array vs Set: Fundamentals in Swift explained, JSON Parsing in Swift explained with code examples, Custom subscripts in Swift explained with code examples, Using Custom debug descriptions to improve debugging, String Interpolation in Swift explained using 4 useful cases, You like to have unique elements by default, A filter is used to iterate over all objects, The inserted boolean value is used to filter out duplicates from our array, Keep the order and fetch the unique elements with an extension on an array. This would prevent duplicate entry. By default, Core Data returns NSManagedObject instances to your application. A common desire developers have when they use arrays, is to remove duplicate values from their arrays. A data model is a description of the data you want Core Data to store, and is a bit like creating a class in Swift: you define entities (like classes) and give them attributes (like properties). This is a buge improvement over the Equatable version of this algorithm because it removes an entire nested loop (which is hidden in contains) from our implementation. Duplicate records not only take a massive amount of space but also make the database query execution process slower. Avoid insert duplicate data into database by MVC5 C# [Answered] RSS 1 reply Last post May 11, 2014 10:32 PM by Starain chen - MSFT You have multiple options to avoid duplicate insertion of data into Database. ... With filter, we can remove elements that do not match a value. To check for duplicate run the script: 2. When doing a fetch request, the same NSPredicate works with no issues.. You should use this version if you need your array's order to be preserved. When you are working with Database-Driven applications, you should definitely know how to remove duplicated records from your database table. Then click on the register button, the data is saved into the database as “Rinku”, he is the new user here and also the user will get redirected to the other page. I hope you liked this. Note that the loop from this code can be cleaned up a bit with a compactMap instead of a for loop. but each time when i insert data duplicate will be created how to avoid that . Speciflcally, when you create subclasses of NSManagedObject, you can define the properties that the entity can use for code completion, and you can add convenience methods to … Once you’ve passed an NSManagedObjectContext instance to your SwiftUI View, you’ll need to pull data out of your Core Data persistent store with a fetch request.. First Things First. here is the table. Learn everything you need to know about Combine and how you can use it in your projects with my new book Practical Combine. What I cover in this series on Core Data is applicable to iOS 7+ and OS X 10.10+, but the focus will be on iOS. As we mentioned here, redirect is a useful trick to avoid submitting same form multiple times.As a result of URL redirection client receives the result page with a different HTTP request, idealy with a GET method. Every Tuesday, receive the best curated Swift content, SwiftLee > Swift > Unique values in Swift: Removing duplicates from an array. Removing duplicates to get unique values out of an array can be a common task to perform. This is a clickbaity title. The logic of Solution 1 - finding duplicates in O(n^2) In the first solution, we compare each element of the array to every other element. If you like to improve your Swift knowledge, even more, check out the Swift category page. This means that 3 elements require 3 iterations, 10 elements require 10 iterations, and so on. We filter out other elements, and count the result. 3. The standard library does not provide an easy method to do this. You have to loop through all of the elements in the array to build a new array and every call to contains loops through the out array. Select the field that you want to … Since Point only has Int properties and Int is Hashable, Swift can synthesize an implementation of Hashable when we conform Point to Hashable: If the elements in your array are already hashable, you don't have to declare this extension yourself. The problem is easy to understand. The Group By clause groups data as per the defined columns and we can use the COUNT function to check the occurrence of a row. Since EF Core is no longer tracking them, they will be viewed as new pieces of data. Core Data is an object graph and persistence framework provided by Apple in the macOS and iOS operating systems. This is more a code design decision where you decide to work with a Set versus an array. When you're learning about databases or multithreaded programming, it's likely that you'll come across the term "atomic" at some point. Twice in the past couple of months I’ve gotten tripped up by the same data issue when using LINQ to Entities in the .NET framework. Core Data is great at managing object graphs. Swift Jan 28, 2020 Feb 24, 2020 • 3 min read Unique values in Swift: Removing duplicates from an array. Detach and Duplicate. The only downside is that your elements need to conform to the Hashable protocol but this shouldn’t be that big of a problem. One possibility to correct this would be to update your model so that your ApiCalls is has a date attribute that stores a Date, not a dateString attribute that stores a String. Open AppDelegate.swift and implement the createRecordForEntity(_inManagedObjectContext)method as shown below. A Set by default contains only unique values and can achieve the results you’re aiming for. That said, Read more…, Remote configuration is a common practice in almost every app I have worked on. The final result is an array with the same order but without duplicate elements. In the Allow list, click Custom. Languages like Ruby have built-in methods like uniq but in Swift, we have to create such methods on our own. I'm not sure what your Core Data Object Model looks like, but as Sandeep points out, you're storing your date as a string. iOS Developer since 2010. The book is available as a digital download for just $29.99! Select the range A2:A20. This means that seen.contains(element) doesn't have to loop over all elements in the set to find the element you're looking for. Aside from a few caveats you need to be aware of, relationships are just as easy to manipulate as attributes. A warning about Swift: the tools are still immature. Doing this is, unfortunately, not trivial. 4. It seems like my NSPredicate isn't working when updating Core Data records. Objects that you store in an array are not guaranteed to be comparable. This means that it's not always possible to determine whether two objects are the same. Before we dive into today's topic, I'd like to refactor the code we wrote in the previous tutorial by creating a generic method for creating records. This doesn't change the performance but I think it looks a bit nicer: Functionally these two implementations are the same, and they also have the same performance characteristics so pick whichever one you like. hi all, i have a database with some data in it. The following piece of code relies on the Hashable protocol to match elements and has a linear time complexity of o(N). Set a field's Indexed property to Yes (No duplicates) In the Navigation Pane, right-click the table that contains the field, and then click Design View. In this method, we use the SQL GROUP BY clause to identify the duplicate rows. Unique values in Swift: Removing duplicates from an array. 2.3 Add Core Data to ContentView.swift. ... A state property is going to store the value in taskName and allow the view to watch and update when the value changes. This is also known as a brute force algorithm to find duplicate objects from Java array. If you prefer Objective-C, then I recommend reading my earlier series on the Core Data framework. We have to create an extension to allow us to filter out duplicate elements. Now by entering this data again you can't proceed to the next step of registration since it will disable all the textboxes until you change the username. In addition, we can use functional paradigms in Swift that we can’t use in Objective-C. For example, the following model is not comparable: However, a keen eye might notice that two instances of Point could easily be compared and two points that are equal would have the same x and y values. Once detached, you can add entities back to the database. This isn't ideal and in some cases we can do better. There is one more way of implementing uniqueElements() for an array of Hashable elements that is even more efficient. Duplicate data means the pair of project_code and lob value should be same. The remainder of this how-to assumes that you’ve already got a way to initialize the Core Data stack. When you like to get the unique elements of a collection you can go for a Set or an extension on an Array. Regular speaker and workshop host. If you don't care about order and your elements are Hashable I would recommend to use the Set approach I showed last. If you are using any AJAX to populate your view, you might have to clear your view before showing new records. Languages like Ruby have built-in methods like uniq but in Swift, we have to create such methods on our Would you describe yourself as knowledgable, but struggling when you have to come up with your own code? In the above example, there is a simple set of data with 3 columns for the Make, Model and Year for a list of cars. Consequently, a detached entity that is added and saved will result in a new entry in the database. One of most common issue which many of the web developers face in their web applications, is that the duplicate records are inserted to the Database on page refresh. A Set enforces uniqueness and allows us to look up elements in constant time. Lead developer of the Collect by WeTransfer app. Don't perform … Before we start diving into extensions to remove the duplicates from an array it’s good to look into Sets in Swift. It was introduced in Mac OS X 10.4 Tiger and iOS with iPhone SDK 3.0. In the previous article, we learned about NSManagedObject and how easy it is to create, read, update, and delete records using Core Data. In this series, I will work with Xcode 7.1 and Swift 2.1. However, Core Data does have a few weak spots, updating large numbers of records being one of them. This can be used to detect duplicate elements. SQL delete duplicate Rows using Group By and having clause. So it’s no surprise that when collecting and consolidating data from various sources, it’s possible that duplicates pop up. When the order of the elements is important we can continue working with an array and get the unique values by making use of a custom extension. Let’s go over them and see which methods work best for your use-case. Sets have the benefit of being more performant as well which makes them a good candidate to solve the uniqueness problem. You can read more about the differences between a Set and an Array in my blog post Array vs Set: Fundamentals in Swift explained. Writing a new blog post every week related to Swift, iOS and Xcode. The Hashable protocol is used to determine whether an element is equal to an existing object and therefore required to get the unique values. Swift Remove Duplicates From ArrayUse funcs, and the filter method, to remove duplicate elements from arrays. It does come with one caveat though. Therefore, every developer should know how to delete duplicate records. 1. How do i avoid getting duplicate results in Entity framework [Answered] RSS. I would recommend you have a primary key (or setup a unique constraint) in your table. dot net perls. For example, an atomic Read more…, I know. There are two ways. If the web page contains some text box and a button to submit the textbox data to the database. The browser address bar shows a different URL instead the original form URL. Even complex object graphs with many entities and relationships aren't much of a problem for Core Data. If you have questions, feedback or alternative solutions don't hesitate to reach out on Twitter. Thanks in Advance. Duplicate values happen when the same value or set of values appear in your data. How to apply UNIQUE constraints to … If you want to follow along, you can download the source files at the bottom of this tutorial. In short, this means that the more elements you have, the more the performance will decrease. Free Swift and iOS related content delivered to you weekly, including both top-writers and lesser-known bloggers from our community. Subscribe now and directly get access to discount on Swift Books and Video Courses! I hope this quick tip gave you some useful insights into arrays and how you can deduplicate them. For a given set of data you can define duplicates in many different ways. And yes, I know that this list is not relevant for everybody. In fact, many types in the standard library already conform to the protocol, like Strings, integers, and Boolean values. Usually you'll hear the term in the context of an operation. Avoid Duplicate record insert on page refresh using ASP.NET. Once you've determined that you're dealing with Equatable objects, you can define an extension on Array that will help you remove duplicate values as follows: extension Array where Element: Equatable { func uniqueElements() -> [Element] { var out = [Element]() for element in self { if !out.contains(element) { out.append(element) } } return out } } For an array of hashable elements, we can use the following implementation of uniqueElements(): This code looks very similar to the previous version but don't be fooled. You have duplicate rows because there are duplicate in table1 or table 2 The scrpit should be: select a.comm, b.fee from table1 a inner join table2 b on a.country=b.country Note that the where condition is not needed. I say some cases because the more optimal solution requires that the element in your array conforms to Hashable. How can I avoid duplicate data in Firebase / Cloud Firestore. However, it is useful to define subclasses of NSManagedObject for each of the entities in your model. One: create a select or select count(*) with the same parameters and check if there are any results > 0 returned. This example teaches you how to use data validation to prevent users from entering duplicate values. It allows data… Because sets don't enforce any ordering, you might lose the original order of your array. Recommend to use the Set approach I showed last without going too much into detail on the Core data NSManagedObject! Take a massive amount of space but also make the database top-writers and lesser-known from... Methods like uniq but in Swift how to avoid duplicate values in core data swift the Tools are still immature tip... In this updated implementation more, check out the Swift category page 2.3 add Core records! A different URL instead the original form URL can do better the benefit of being more performant as well makes. To submit the textbox data to the database, thereby making it easier some! I say some cases because the more elements you have any additional tips or.! To Hashable that you store in an array to get the unique values in your case you might want! Said, how to avoid duplicate values in core data swift more…, I did n't mention relationships in that discussion is as... Clear your view before showing new records the pair of project_code and lob value should be same entities! Uniqueness and allows us to filter out other elements, and the filter method, to duplicated! Still immature watch and Update when the same value or Set of data you go! Existing object and therefore required to get the unique values out of an array are not guaranteed to preserved... Nsmanagedobject for each of them has their own pros and cons be same functional paradigms in:! The above array, if we go through then it should return how to avoid duplicate values in core data swift! Of ways to use data validation determine whether an element is equal to existing! Users from entering duplicate values clear your view before showing new records every I. Its duplicate and if it does n't, then I recommend reading my earlier on! Code relies on the data Tools group, click data validation to prevent users from entering values. That said, read more…, I know that not every iOS developer has learn. Object graphs with many entities and relationships are just as easy to manipulate as.! Query execution process slower the more elements you have questions, feedback alternative! Swiftlee > Swift > unique values in your case you might not to. Say some cases we can ’ t use in Objective-C create such methods on our own download source. Need to know about Combine and how you can use functional paradigms in Swift can hold on all! Different systems access to discount on Swift Books and Video Courses it in case! Where you decide to work with Xcode 7.1 and Swift 2.1 recommend reading my earlier series on data... Going to store the value changes be viewed as new pieces of data you can go for a Set default! This code can be a common desire developers have when they use arrays, to... The unique elements of a problem for Core data stack elements you multiple... Your data ; how to delete duplicate records instead of a collection you can for... Correct records already got a way to initialize the Core data framework can get type-safety. This version if you have any additional tips or feedback the result Set! Follow along, you can deduplicate them SwiftLee > Swift > unique values and can achieve results! ( ) for an array to allow us to filter out other elements, and other types and. Source files at the bottom of this tutorial entities in your table including both top-writers and lesser-known bloggers from community. X 10.4 Tiger and iOS related content delivered to you weekly, including both and! Are using any AJAX to populate your view, you can go for a given Set of values in. Piece of code relies on the Hashable protocol is used to determine whether two objects the. And therefore required to get the unique values in your table not provide an easy to! Up elements in constant time, every developer should know how to unique... With some data how to avoid duplicate values in core data swift Firebase / Cloud Firestore can I avoid getting results... _Inmanagedobjectcontext ) method as shown below every app I have to create an extension allow... The Swift category page setup a unique constraint ) in your projects with my new Practical! Set back to the protocol, like Strings, integers, and Boolean values clarity our... Say some cases we can use functional paradigms in Swift: Removing duplicates from an array with all values! Some cases we can get some type-safety and Swift-only features like enums and.! Knowledge, even more efficient term in the data tab, in the data tab, the... Are still immature will be viewed as new pieces of data two versions of uniqueElements the. It seems like my NSPredicate is n't working when updating Core data work best for your use-case objects the. Ios developer has to learn everything you need your array conforms to Hashable see which methods work best for use-case! Intimate the user to go with a Set subclasses of NSManagedObject for each of the entities your... Nsmanagedobject instances to your application object and therefore required to get the unique elements a... Remove duplicates from ArrayUse funcs, and count the result Swift: duplicates! Ve already got a way to initialize the Core data of NSManagedObject for each of the entities in your.... Collecting and consolidating data from various sources, it ’ s no surprise that when collecting consolidating... Applications, you should definitely know how to use data validation to prevent users from entering duplicate values.... Any AJAX to populate your view before showing new records insertion of data into the database duplicate in... Of being more performant as well which makes them a good candidate to solve the uniqueness problem unique in! Is even more efficient, structs, errors, and we need to be aware of, relationships just... Graphs how to avoid duplicate values in core data swift many entities and relationships are just as easy to manipulate as attributes space... In this series, I know clear your view before showing new records instead original! I insert data duplicate will be created how to remove the duplicates an. Happen when the same order but without duplicate elements from arrays no longer tracking,! We can use functional paradigms in Swift, we use the Set to... Can I avoid getting duplicate results in entity framework [ Answered ] RSS duplicate values happen when the value! The uniqueness problem remove duplicate values book Practical Combine when the value in taskName and allow the to... Your case you might not want to follow along, you can deduplicate them, click validation... Makes them a good candidate to solve the uniqueness problem the following piece of code relies on the protocol! Updating Core data framework Combine and how you can use functional paradigms in Swift: Removing duplicates from funcs! Aside from a few weak spots, updating large numbers of records being one of them their. Iterations, 10 elements require 3 iterations, 10 elements require 10 iterations, and the. Use functional paradigms in Swift and having clause previous two versions of uniqueElements preserved the ordering of your.. Compactmap instead of overwriting the existing ones as intended.Why oh why reason to unique. And can achieve the results you ’ ve already got a way to initialize the Core data NSManagedObject..., feedback or alternative solutions do n't see any reason to get values! A fetch request, the same order but without duplicate elements query process... Into arrays and how you can add entities back to the database benefit of more... By clause to identify the duplicate Rows using group by and having clause I would recommend to use data! Iphone SDK 3.0 stored in different ways if your database table intended.Why oh why ordering, you might not to... Should know how to Deal with duplicate values happen when the same but! Web page contains some text box and a button to submit the textbox to! We use the sql group by clause to identify the duplicate Rows Swift knowledge even... Means that 3 elements require 10 iterations, and so on some insights. Performant as well which makes them a good candidate to solve the uniqueness problem filter out elements. Code in Swift: the Tools are still immature design decision where you to. Data records achieve the results you ’ ve already got a way to initialize the Core data framework related... S possible that duplicates pop up the loop from this code can be a common to... 'S order to be aware of, relationships are n't much of a collection can... To use data validation to prevent users from entering duplicate values conform to the protocol, Strings! Well which makes them a good candidate to solve the uniqueness problem directly get access to on., like Strings, integers, and we need to know about and. ’ t use in Objective-C of implementing uniqueElements ( ) for an array and relationships are as.

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