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. The remainder of this how-to assumes that you’ve already got a way to initialize the Core Data stack. 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. 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. The only downside is that your elements need to conform to the Hashable protocol but this shouldn’t be that big of a problem. Data is stored in different ways in different systems. So it’s no surprise that when collecting and consolidating data from various sources, it’s possible that duplicates pop up. Duplicate data means the pair of project_code and lob value should be same. However, Core Data does have a few weak spots, updating large numbers of records being one of them. Since EF Core is no longer tracking them, they will be viewed as new pieces of data. This is a clickbaity title. Writing a new blog post every week related to Swift, iOS and Xcode. Before we start diving into extensions to remove the duplicates from an array it’s good to look into Sets in Swift. I have to check on some system info and insert data into the database. The browser address bar shows a different URL instead the original form URL. You could go for an NSOrderedSet but this class does not give you type completion and you’ll have to work with Any instances. 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. This can be used to detect duplicate elements. If the web page contains some text box and a button to submit the textbox data to the database. Unique values in Swift: Removing duplicates from an array. There is one more way of implementing uniqueElements() for an array of Hashable elements that is even more efficient. When doing a fetch request, the same NSPredicate works with no issues.. How do i avoid getting duplicate results in Entity framework [Answered] RSS. In the previous article, we learned about NSManagedObject and how easy it is to create, read, update, and delete records using Core Data. Creating NSManagedObject Subclasses. dot net perls. Duplicate records not only take a massive amount of space but also make the database query execution process slower. ... A state property is going to store the value in taskName and allow the view to watch and update when the value changes. Feel free to contact me or tweet to me on Twitter if you have any additional tips or feedback. 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. That said, Read more…, Remote configuration is a common practice in almost every app I have worked on. I don't see any reason to get duplicated values if your database has correct records. In the above array, if we go through then it should return project_code : 1 If anyone can write a code in Swift .. 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. Don't perform … Usually you'll hear the term in the context of an operation. 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). It seems like my NSPredicate isn't working when updating Core Data records. I hope you liked this. The implementation should look familiar if you read the previous tutorial. 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. 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. 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. Note that I defined a Set in this updated implementation. 4. You can read more about the differences between a Set and an Array in my blog post Array vs Set: Fundamentals in Swift explained. Let’s go over them and see which methods work best for your use-case. In the Allow list, click Custom. We can get some type-safety and Swift-only features like enums and optionals. For example, an atomic Read more…, I know. 2. iOS Developer since 2010. Custom debug descriptions can help you debug your own custom objects, structs, errors, and other types. This means that 3 elements require 3 iterations, 10 elements require 10 iterations, and so on. This is more a code design decision where you decide to work with a Set versus an array. Removing duplicates to get unique values out of an array can be a common task to perform. By default, Core Data returns NSManagedObject instances to your application. Select the field that you want to … 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. How can I avoid duplicate data in Firebase / Cloud Firestore. A Set enforces uniqueness and allows us to look up elements in constant time. The Hashable protocol is used to determine whether an element is equal to an existing object and therefore required to get the unique values. You should use this version if you need your array's order to be preserved. In short, this means that the more elements you have, the more the performance will decrease. 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. It was introduced in Mac OS X 10.4 Tiger and iOS with iPhone SDK 3.0. The following piece of code relies on the Hashable protocol to match elements and has a linear time complexity of o(N). 2.3 Add Core Data to ContentView.swift. There’s a lot of ways to achieve the same result and each of them has their own pros and cons. 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. 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. 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 is also known as a brute force algorithm to find duplicate objects from Java array. Swift can bring clarity to our code, thereby making it easier in some ways to use Core Data. 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. 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. Every Tuesday, receive the best curated Swift content, SwiftLee > Swift > Unique values in Swift: Removing duplicates from an array. If you don't care about order and your elements are Hashable I would recommend to use the Set approach I showed last. 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). If keeping the order is important in your case you might not want to go with a Set. You handle the appropriate exception and intimate the user. 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. Prevent Duplicate Entries. Objects that you store in an array are not guaranteed to be comparable. I say some cases because the more optimal solution requires that the element in your array conforms to Hashable. One: create a select or select count(*) with the same parameters and check if there are any results > 0 returned. When you like to get the unique elements of a collection you can go for a Set or an extension on an Array. here is the table. How to Deal with Duplicate Values in Your Data; How to Deal with Duplicate Values in Your Data. Subscribe now and directly get access to discount on Swift Books and Video Courses! Avoid Duplicate record insert on page refresh using ASP.NET. How to apply UNIQUE constraints to … The book is available as a digital download for just $29.99! If you like to improve your Swift knowledge, even more, check out the Swift category page. 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. Without going too much into detail on the differences it’s good to know that a Set is not maintaining the order. If you are using any AJAX to populate your view, you might have to clear your view before showing new records. 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. We can then convert the set back to an array to get an array with all duplicate values removed. A common desire developers have when they use arrays, is to remove duplicate values from their arrays. It does come with one caveat though. Languages like Ruby have built-in methods like uniq but in Swift, we have to create such methods on our own. In addition, we can use functional paradigms in Swift that we can’t use in Objective-C. hi all, i have a database with some data in it. It allows data… In this series, I will work with Xcode 7.1 and Swift 2.1. We have to create an extension to allow us to filter out duplicate elements. 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. You have multiple options to avoid duplicate insertion of data into Database. Removing duplicates to get unique values out of an array can be a common task to perform. Once detached, you can add entities back to the database. Core Data is an object graph and persistence framework provided by Apple in the macOS and iOS operating systems. When you are working with Database-Driven applications, you should definitely know how to remove duplicated records from your database table. 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 … For a given set of data you can define duplicates in many different ways. In the table, we have a few duplicate records, and we need to remove them. Learn everything you need to know about Combine and how you can use it in your projects with my new book Practical Combine. Because sets don't enforce any ordering, you might lose the original order of your array. Would you describe yourself as knowledgable, but struggling when you have to come up with your own code? When I do a Batch Update, it just creates new duplicate records instead of overwriting the existing ones as intended.Why oh why? 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. Free Swift and iOS related content delivered to you weekly, including both top-writers and lesser-known bloggers from our community. Open AppDelegate.swift and implement the createRecordForEntity(_inManagedObjectContext)method as shown below. SQL delete duplicate Rows using Group By and having clause. Regular speaker and workshop host. 3. I hope this quick tip gave you some useful insights into arrays and how you can deduplicate them. 1. Even complex object graphs with many entities and relationships aren't much of a problem for Core Data. Swift Jan 28, 2020 Feb 24, 2020 • 3 min read Unique values in Swift: Removing duplicates from an array. Lead developer of the Collect by WeTransfer app. This means that it's not always possible to determine whether two objects are the same. When you're learning about databases or multithreaded programming, it's likely that you'll come across the term "atomic" at some point. Sets have the benefit of being more performant as well which makes them a good candidate to solve the uniqueness 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. If you have questions, feedback or alternative solutions don't hesitate to reach out on Twitter. A Set by default contains only unique values and can achieve the results you’re aiming for. Select the range A2:A20. To check for duplicate run the script: 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. The final result is an array with the same order but without duplicate elements. If you prefer Objective-C, then I recommend reading my earlier series on the Core Data framework. Doing this is, unfortunately, not trivial. I would recommend you have a primary key (or setup a unique constraint) in your table. By Alan Anderson, David Semmelroth . Arrays in Swift can hold on to all kinds of data. Swift Remove Duplicates From ArrayUse funcs, and the filter method, to remove duplicate elements from arrays. Consequently, a detached entity that is added and saved will result in a new entry in the database. 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 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. In this method, we use the SQL GROUP BY clause to identify the duplicate rows. ... With filter, we can remove elements that do not match a value. 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. Duplicate values happen when the same value or set of values appear in your data. On the Data tab, in the Data Tools group, click Data Validation. I know that not every iOS developer has to learn everything on this list. A warning about Swift: the tools are still immature. 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. If you want to follow along, you can download the source files at the bottom of this tutorial. Swift + Core Data . With createRecordForEntity(_inManagedObjectContext) im… 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. Core Data is great at managing object graphs. 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… but each time when i insert data duplicate will be created how to avoid that . Therefore, every developer should know how to delete duplicate records. 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. In fact, many types in the standard library already conform to the protocol, like Strings, integers, and Boolean values. Detach and Duplicate. 3.2 Adding the task to Core Data. The problem is easy to understand. It's much better. However, it is useful to define subclasses of NSManagedObject for each of the entities in your model. This would prevent duplicate entry. This example teaches you how to use data validation to prevent users from entering duplicate values. 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 } } We filter out other elements, and count the result. If it matches then its duplicate and if it doesn't, then there are no duplicates. 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. The previous two versions of uniqueElements preserved the ordering of your input. EF Core will view these objects as entirely unrelated to the database. 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. This isn't ideal and in some cases we can do better. Thanks in Advance. There are two ways. Aside from a few caveats you need to be aware of, relationships are just as easy to manipulate as attributes. Note that the loop from this code can be cleaned up a bit with a compactMap instead of a for loop. And yes, I know that this list is not relevant for everybody. 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. For the Point struct I showed you earlier this is easy to achieve. The standard library does not provide an easy method to do this. 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Related content delivered to you weekly, including both top-writers and lesser-known bloggers from our.... Use in Objective-C up elements in constant time always possible to determine whether an is! Feb 24, 2020 • 3 min read unique values in your case you might lose the form... Unique constraints to … avoid duplicate data means the pair of project_code and lob value should same. Have, the same order but without duplicate elements from arrays this updated implementation only unique values Swift! Working when updating Core data stack 1 if anyone can write a in! A state property is going to store the value in taskName and allow the view watch. Value should be same 's not always possible to determine whether an element is equal to existing..., we have to clear your view, you can use it in your case you might not to! Are not guaranteed to be aware of, relationships are just as easy to manipulate attributes! 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