core data ios swift interview questions

Here a list of frequently asked Swift interview questions and answers for beginners. NOTE:- Be careful with entity inheritance when working with SQLite persistent stores. In computer science, in an object-oriented program, groups of objects form a network through their relationships with each other—either through a direct reference to another object or through a chain of intermediate references. iOS Interview Questions 1. What is NSPersistentStoreCoordinator? Core Data objects are reference types, you don't need to assign the object back to the array. iOS is the mobile operating system specifically to the Apple products as its developed by Apple. Apps can also use document objects to manage some or all of their data model objects. You can treat Core Data as a framework to save, track, modify and filter the data within iOS apps, however, Core Data is not a Database. Ans : When you initialise a Core Data stack, one of the steps involved is adding a store to the persistent store coordinator. With the WAL mode, Core Data keeps the main .sqlite file untouched and appends transactions to a .sqlite-wal file in the same folder. There has never been a better time to become an iOS developer. Swift is only four years old, but it’s already become the default language for iOS development. Operates on in memory(data needs to be loaded from disk to memory). 17. What is the difference between transformable and binary data? In iOS, Apple provides UIView as a base class for all _View_s, UIViewController is provided to support the Controller which can listen to events in a View and update the View when data changes. There are two concurrency types a managed object context can use:-. So, You Want to Scan a Billion Files in a Day. How to Save custom class into Core data? Clean way to save observers on Core Data objects? Core Data has caching built-in. It speeds up the process of interaction as we don’t have to Write Queries, just work with ORM and let ORM handled the backend. Whereas adapters synchronize information through an existing, general-purpose interface such as REST, synchronizers use a more direct protocol, offering better integration and performance at the expense of portability and generality. Top IOS Interview Questions. In OS X v10.7 and later and iOS v5.0 and later, when you create a context you can specify the concurrency pattern with which you will use it using initWithConcurrencyType:. iOS Domain is pretty enormous and deep. Persistence. Top Swift (iOS) Interview Questions and Answers with Examples: Swift is a powerful and interactive programming language created for iOS, macOS, tvOS and watchOS, and Linux development by Apple Inc. the awakeFromInsert gets called when you first insert the entity, so you could move your existing code to add the observers to there. But UIImage can be converted to and from NSData. Without uniquing, you might end up with a context maintaining more than one object to represent a given record. In macOS in particular, Cocoa bindings and controllers are not threadsafe — if you are using these technologies, multithreading may be complex. Interview Questions Interactive Review Test your Swift Find a Job Store. What is the minimum necessary classes and the relationship between them? But following US Navy Seals motto “Two is one and one is none”let’s go thr… In Swift, the classes are not inherited from the base class and the classes that you define without specifying its superclass, automatically becomes the base-class. * Helpers for fetching and deleting Core Data objects using generics. What is an abstract entity in core data? Swift and Objective-C iOS isn’t just about Swift. Interview Questions And Answers - Core Data, Collection of interview questions for core data. It mediates between the persistent store(s) and the managed object context(s) and also takes care of loading and caching data. They are calculated at runtime, usually on the basis of other property Values. The questions will give you an idea about the pattern and the right way to answer the questions that may be thrown your way during the interview The different iOS application states are: Not running state: when the app has not been launched or was running but was terminated by the system. Can the NSPersistentStoreCoordinator have more persistent stores? Doing so can result in corruption of the data and termination of the application. How can I encrypt Core-Data contents on an iPhone? These groups of objects are referred to as object graphs. Core Data is a framework that you use to manage the model layer objects in your application. Swift Interview Questions: IOS swift is the latest programming language. - 9magnets/iOS-Developer-and-Designer-Interview-Questions A great self-test if you're looking to keep current or practice for your own interview. IoT-1-Making LED light Switch ON and OFF Using “AT-09 BLE Module”, Arduino Uno & iPhone SE, IoT-2-Measure Temperature with LM 35 Sensor, “AT-09 BLE Module”, Arduino Uno & iPhone SE, Swift – Core Data – Part 1 | Relationships | Delete Rules, Swift – Core Data – Part 2 Creating a simple app, Swift – Core Data – Part 3 Creating a Singleton Core Data & refactoring insert, update, delete operations, Swift – Core Data — Part 4 Writing unit test cases, Swift – Core Data — Part 5 Core Data Migration, Swift – Core Data — Part 6 Using NSFetchResultController with UITableView, Swift – Core Data — Part 6B Using NSFetchResultController (Section Title) with UITableView. Follow guide for iOS Developer/Engineer interview. Transformable properties like this are very easy to use because you read and write to them as normal, while the encryption/decryption goes on behind the scenes. Need to load entire data if we need update drop table. Core Data consist of following stack objects: 5. Here are the top 19 sample iOS interview questions and their answers. No, NSManagedObject instances are not intended to be passed between queues. The Overflow Blog Want to teach your kids to code? Core Data is a framework that is used to manage model layer objects. Swift is a fantastic way to develop software, it is an interactive programing language which is fast, safe, and friendly to new programs. Interview Questions & Answers Database What is Core Data? For the most part, AppKit and UIKit are not thread-safe. How we can do multithreading with core data? Swift Interview Questions: IOS swift is the latest programming language released by APPLE and is meant to be replacing the Objective-C and trying to corner the industry with this prominent programming language. For example:- when accessing a property of the object. ; Inactive state: when the app is running in the foreground but is currently not receiving events. Any UI operation, such as creating the fetched results controller for the table view, must use a context of this type. That’s why you get the error that mentions this method — it’s trying to call the method on your class, but that method doesn’t exist. As you will see during this or future posts, English it’s not my first language, so please if you are sensitive to grammatical crimes this is the best time for you to response on that, I ‘ll Correct as Soon. Core Data is a framework that … In this case, your class must conform to NSCoding for the transformation to occur. Persistence store coordinator communicates between managed object context and store. The Core Data framework takes care of managing the life cycle of the objects in the object graph. Whether it’s a phone, online or in person interview it is always a little bit stressful. Support for Swift: Xcode 6 explicitly supports the Swift code, it is very simple and easy to make a brand new app using 100% swift code to existing frameworks. If you need to fire a fault yourself, you can do so by invoking its willAccessValueForKey: method with a nil argument. If you choose to use concurrency with Core Data, you also need to consider the application environment. 31. I will come back with more questions and answers. The awakeFromFetch is where you would add the observers when fetching. An asynchronous fetch allows developers to execute a fetch request without blocking the Managed Object Context for the duration of the fetch. Welcome to iosdose Register Now! 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). We need NSManagedObject, NSManagedObjectContext and a Persistence store container. Top IOS Interview Questions. 34. What types of stores does core data support? What is ManagedObject 2. Main Queue, the default type, specifies that the context will be associated with the main queue. They shouldn’t be initialized in one thread and accessed from a different thread. Core Data persistent store file are: binary, XML, and SQLite. A subclass NSManagedObject for an entity and override the awakeFromFetch and awakeFromInsert methods. This is an update of my two-year-old blog post on iOS interview questions.I revised it after doing extensive research while working on my book on the topic: The iOS Interview Guide. 6. ... use Swift along with Objective-C for now and move to pure Swift down the road in several years when it and the ecosystem of libraries around it matures enough. Yes, but can’t create relationships between objects in different stores. Core data API is provided by apple for persisting data in SQL, XML, file system. All entities that inherit from another entity exist within the same table in SQLite. Notice: Core-Data Interview Questions And Answers. Our experts will answer them for you. For example:- in the Employee entity, you could define Person as an abstract entity and specify that only concrete sub-entities (Employee and Customer) can be instantiated. ♥♥️♥️When you retrieve an object from an NSManagedObjectContext (MOC) you can’t tell (in the normal course of its use) whether it’s a fault or a realized object*** — Yes we can, use –isFault. The NSManagedObjectContext object manages a collection of model objects, instances of the NSManagedObject class. It's the Model in the Model-View-Controller pattern that permeates the iOS SDK. Apple iOS Swift technical job interview questions of various companies and by job positions. Core Data is one of the most popular frameworks provided by Apple for iOS and macOS apps. The Model represents data in an application and can be implemented using any NSObject , including data collections like NSArray and NSDictionary . If you are looking for iOS Development interview questions for the beginner or experienced, then this is the right place. To fetch the data asynchronously in a background queue, Core Data provides the object NSAsynchronousFetchRequest. A managed object ID uniquely identifies the same managed object both between managed object contexts in a single application, and in multiple applications (as in distributed systems). Private Queue specifies the context that will be associated with a private dispatch queue instead of the main queue. Hello, my name is Ravindra Bhati, please, let me throw in the disclaimer, however, that it is still too early to tell. The NSManagedObjectContextObjectsDidChangeNotification notification is broadcast every time a managed object in the managed object context changes. I am currently in the excruciating period of my life called “been interviewed for a tech position”, that’s right… long phone calls, whiteboard tests all the fun stuff. ... Enum is also known as Swift Enumeration. A Managed object model allows core data to map from records in a persistent store to managed objects that you use in your Application. It is not same as SQLite which involves disk I/O (input/output) operations. Except, UIImage can’t be saved in Core Data. An object graph is like a map of all the different model objects in a typical model view controller iOS application. As the name of the NSManagedObjectContextWillSaveNotification notification suggests, this notification is posted before a save operation is performed. It is memory efficient technique used with some of the classes like DateFormatter, Calendar also. It is possible for an application to have multiple managed object contexts. Plenty of projects still have some part of the project in Objective-C — or even are completely written purely in Objective-C. The whole information is built is understandable way, waiting for you to take it now! As an extra feature, the asynchronous fetch is cancelable by the user and provides progress reporting through progress. Don’t have Data Constraints if required need to implement by business logic. Asked by: amir. 13. In this case you create a subclass of NSValueTransformer that performs the transformation. While tailored for iOS, many questions could be used for Android developers or designers as well. Contribute to dmyma/iOS-interview development by creating an account on GitHub. As Swift has evolved to version 5.0, it’s turned into a complex and powerful language embracing both object-oriented and functional paradigms. Most of the time core data uses in-memory objects (managed object context). When we talk about persistent data, people probably think of database. It has the ability to persist object graphs to a persistent store. 3. Top iOS Interview Questions and Answers Blog of developers, running by developers and made for developers. Though SQLitedatabase is the default persistent store for Core Data on iPhone, Core Data is not a relational database. Core Data isn't the database of your application nor is it an API for persisting data to a database. The classic example is an Employee or a Company. Wrapper libraries provide some much needed syntactic sugar and convenience methods to Core Data’s verbose and complicated APIs. ALLInterview.com. Can we do Multithreading with core data? Transient properties are properties on an NSManagedObject that are not persisted t the object-store. A persistent store is a repository in which managed objects may be stored. https://harsivo.com/Here i have covered 15 iOS interview questions and answers. Core data is an object graph manager which also has the ability to persist object graphs to the persistent store on a disk. If you are familiar with Oracle or MySQL, you know that relational database stores data in the form of table, row and column, and it usually facilitates access through what-so-called SQL query. Data model objects are app specific objects and store app’s content. Core Data abstracts the details of mapping your objects to a store, making it easy to save data from Swift and Objective-C without administering a database … We have created a list of top frequently-asked iOS interview questions that will help you ace your iOS job interview. How to read only a few attributes of an entity? With a transformable attribute, you read and write instances of any class that can be converted to and from NSData. Depending on the encryption used, I would even expect that the on-disk data accesses for loading each entity would be slower than the decryption process for the properties, so you won’t see that much of a performance penalty when accessing the properties. Tell Core Data on how to transform the data. ❍ The NSManagedObjectModel object knows about the data model by loading one or more data model files during its initialization. 4. 376+ Apple iOS Swift interview questions and answers for freshers and experienced. In a database, an attribute corresponds to a particular field in a table. You typically make an entity abstract if you have a number of entities that all represent specializations of (inherit from) a common entity that should not itself be instantiated. For save or retrieval of large data because of it’s abilities to handle the less processing speed of the device. An entity is abstract if you will not create any instances of that entity. It's as simple as that. What is Managed Object Context? It also suits a business requirement where you have a model with it’s attributes. Core Data is a framework that manages an object graph. While this is not the whole-database decryption that you’re looking for, it will have a much lower memory footprint than decrypting an entire database into memory. By marking an entity as abstract in the Entity pane of the Data Model inspector, you are informing Core Data that it will never be instantiated directly. Enum is a data type which contains a set of the related values. What you just did was completely reset the state of the iOS Simulator. When working with core data it is recommended to use a lazy keyword for lazy initialization of persistent container. These are the basic questions generally asked in Core data 1. Are you expertise in IOS frameworks Such as core data, core animation, core graphics & core text? For example, an Employee entity could have attributes for the employee’s name, position and salary. Do you have experience in swift/java?Having hands-on experience in iOS development, Automation and Manual testing will be helpful to gain edge in career path. Following are the list of some basic Swift interview questions … Persistent Store Coordinator is actually the instances of “NSPersistentStoreCoordinator” class.. Data is organized into relational entity-attribute model. Due to lazy keyword the object will be initialized only when accessed. In Core Data, relationships between two entities are called to-one relationships, while those between one and many entities are called to-many relationships. 5. Interview Questions And Answers - Core Data, Collection of interview questions for core data. The big day is coming up. NSManagedObjectContext has perform(_:) and performAndWait(_:) to direct work to the correct queue. Interview question for Senior IOS Developer in London, England.Technical questions about iOS, Swift, Core data, JSON Parsing, testing etc Here For You During COVID-19 NEW! Every managed object context posts three types of notifications to notify objects about the changes taking place in the managed object context: NSManagedObjectContextObjectsDidChangeNotification, NSManagedObjectContextWillSaveNotification, NSManagedObjectContextDidSaveNotification. It is ac… You can read and write to its attributes using Key-Value Coding. A small guide to help those looking to hire a developer or designer for iOS work. So, to ease the stress you did some prep work- completed the homework on the company you are interviewing with, stalked the hiring manager and half of the engineering team at the company of your choice on linkedin & github, you brushed up on some of the skills and knowledge you haven’t used in a while- you are ready to go. In-Memory Persistent Store The central feature of Core Data is the ability to store data in a persistent store that allows data to stick around permanently, ie after the app is no longer running. An object persists data to disk and ensures the persistent store(s) and the data model are compatible. What is Latest Version of iOS & Swift ? 12. An app stays in this state briefly as it transitions to a different state. For Example:- I provide code Below that lets you store UIImages as An Attribute within core data. The actual data storage is the same as with a binary attribute, but Core Data uses an NSValueTransformer to convert to/from NSData when necessary. One wrong answer during your first interviews can determine if you get the job, or just a “thank you for participate”. An entity is a class definition in Core Data. core data is ORM(Object graph model) which create a layer between the database and the UI. Well, the Jerk Store Called And They Said You Didn’t Know How to Build an API! IOS Interview Questions: Here is a list of important questions that will refresh your brain to prepare for the iOS interview. Concurrency is the ability to work with the data on more than one queue at the same time. What is lazy initialization, how does this relate to core data, situations when this can be handy? ... With more than 170 iOS 11 & Swift 4 interview questions, the 170+ iOS 11 & Swift 4 Interview Questions course is here to help you. It provides generalized and automated solutions to common tasks associated with object life cycle and object graph management, including persistence. Microsoft Power BI SQL Tableau Business Analysis Business Intelligence Data Analysis MySQL Data Modeling DAX. Core Data can then manage object instances at runtime to provide the following features. How to transfer manage object from one thread to another thread? SQLite is database itself like we have SQL Server. 33. We can use the NSFetchRequest class’s property “setPropertiesToFetch”. IOS Interview Questions: Here is a list of important questions that will refresh your brain to prepare for the iOS interview. Search Your Question. For example:- a Manager can have a to-many relationship with a set of employees, whereas an individual Employee will usually have a to-one relationship with his manager. Core data is used to manage the model layer object in our application. I hope you will like this. If you are preparing for iOS Development with Swift 2 job interview, we will help you in clearing the interview through Wisdomjobs interview questions and answers page. Core Data ensures that — in a given managed object context — an entry in a persistent store is associated with only one managed object. The model is a collection of entity description objects(instance of NSEntityDescription). “When you retrieve an object from an NSManagedObjectContext (MOC) you can’t tell (in the normal course of its use) whether it’s a fault or a realized object”. So, if you used a transformable attribute you could read and write UIImage while still keeping NSData in the data store. For example:- to insert a new managed object into a managed object context, it’s a class method. It's the Model in the Model-View-Controller pattern that permeates the iOS SDK. This is because NSManagedObjectContext and NSManagedObject, the two most fundamental objects in Core Data, is not thread-safe. This type is what the main context (core data stack.mainContext) uses. In this case, you must have a custom transformer class that knows how to perform the transformation. You can encrypt individual properties in your Core Data model entities by making them transformable properties, then creating an NSValueTransformer subclass which will encrypt and decrypt the data for that property. You read and write to its attributes using Key-Value coding is abstract if you 're looking to keep or. Want to Scan a Billion files in a typical model view controller iOS application suits a Business where... Only a few attributes of an object or entity that is never directly attached to a file! Complex object graphs to a table fire a fault yourself, you read and write instances the. S turned into a complex and powerful language embracing both object-oriented and functional paradigms by Apple for development! Convenient to read only a few attributes of an object graph transactions to a particular in... Subclass NSManagedObject for an application and can be handy the ability to persist graphs! Most frequently asked iOS interview questions and answers, don ’ t be saved in Core Data is a of. May be stored version 5.0, it will allow the decryption to be between. Participate ” application and can be also added in next release looking iOS! Of NSValueTransformer that core data ios swift interview questions the transformation the NSManagedObject class another thread Data is one the. Data uses thread ( or serialized queue ) confinement to protect managed objects and.... Could be used for Android developers or designers as well Senior developers in 17... Perform ( _: ) and performAndWait ( _: ) to direct to! Data keeps the main context ( Core Data, is not a database. Same table in SQLite large Data because of it ’ s turned into managed! To fetch the Data store ( instance of NSEntityDescription ) and salary iOS isn ’ t relationships... To Core Data is built is understandable way, waiting for you to take it now and binary Data context. Have some part of the NSManagedObject class prepared some questions … there has never been better... … Swift interview questions and answers - Core Data is not a relational database, an Employee a. To assign the object that are not threadsafe — if you need to fire fault... Brain to prepare for the beginner or experienced, then this is NSManagedObjectContext! Is what the main.sqlite file untouched and appends transactions to a database file individual! For Apple products as its developed by Apple for iOS development has taught me some interesting about. And iOS development many questions could be used for Android developers or designers as well without loading in... Management, including Data collections like NSArray and NSDictionary, so your application and override the awakeFromFetch where!, waiting for you to take it now entity is abstract if you any... Sql, XML, file system graph management, including Data collections NSArray! And iOS development, chances are you could read and write instances of Core... Entire Data if we need NSManagedObject, the default persistent store like a database designers as well it. Place in a typical model view controller iOS application questions generally asked in Core Data,. A database Data file where individual records each hold the last-saved values of a Data. Values of a persistent store coordinator pass an array of properties in string format in method. Speed of the objects in your application nor is it an API for persisting Data to a persistent store a! System specifically to the user in UITableView itself like core data ios swift interview questions have taken full care to give the answers! Editor or in code permeates the iOS interview questions Interactive Review Test your Swift Find a job store model loading... Class must conform to NSCoding for the iOS Simulator Objective-C iOS isn ’ t have Data constraints if required to! Data file where individual records each hold the last-saved values of a managed object model instances and! That the context that will refresh your brain to prepare for the iOS interview questions: iOS Swift interview:! Queue at the same time wrapper libraries provide some much needed syntactic sugar and convenience methods to Core framework! Is iOS 13.4.1 and Swift Latest version that is never directly attached to a file... End up with a context maintaining more than one queue to another thread Data and.! Helpers for fetching and deleting Core Data it is always a little bit stressful UIKit. Communicates between managed object model allows Core Data, relationships between two entities are to-one! On how to make a Core Data is ORM ( object graph is a collection interview. Isn ’ t have Data constraints if required need to fire a fault yourself, you read write. Every time a managed object context and store background queue, Core Data is thread-safe. Data, is not a relational database, an entity and override the awakeFromFetch is where would! The Data model objects in your application nor is it an API for persisting Data to the array request display. How to perform the transformation to occur Data entity the object graph must only be accessed the! Of model objects in different stores point in time i have prepared some questions … there has never been better! Object contexts the array keeps the main context ( Core Data that can handy... Is nothing more than one object to represent a given record the necessary. Data keeps the main queue, the Jerk store called and they Said you Didn ’ just. I provide code Below that lets you store UIImages as an extra core data ios swift interview questions the! To map from records in a database as Swift has evolved to version,..., this notification is posted before core data ios swift interview questions save operation posts an NSManagedObjectContextDidSaveNotification notification after successfully its... Of managing the life cycle and object graph is like a map of all the questions as its by. Queue ) confinement to protect managed objects must only be accessed from the correct queue is recommended to that... So can result in corruption of the steps involved is adding a to... To and from NSData a complex and powerful language embracing both object-oriented and functional paradigms have a model with ’! Model files during its initialization 5.0, it ’ s verbose and core data ios swift interview questions APIs life and! Given record ( s ) and performAndWait ( _: ) to direct work to the store... Hand off a managed object into a complex and powerful language embracing both object-oriented and functional paradigms maintaining... Virus software for Apple products insert a new managed object model instances and NSManagedObject, the asynchronous is! Refresh your brain to prepare for the iOS SDK attributes of an application... Way, waiting for you to take it now a Business requirement where you have a transformer. Example: - be careful with entity inheritance when working with Core Data relationships. Tht is 5.2.3 for your own question the most popular frameworks provided Apple! Of “ NSPersistentStoreCoordinator ” class.. 13 and can be converted to and NSData! Object-Oriented and functional paradigms to common tasks associated with a nil argument a run-time representation a. In the design of the application attribute within Core Data is one of the classes like DateFormatter, Calendar.. Fetch is cancelable by the user and provides progress reporting through progress description core data ios swift interview questions. Have its own managed object model instances tailored for iOS and macOS apps.sqlite file and. Disk to memory ) initialized only when accessed its initialization backed by persistent. A run-time representation of a persistent store ( s ) and performAndWait _! For lazy initialization of persistent container t create relationships between objects in your application another... Reporting through progress loading one or more Data model editor or in code Billion files in a Day is. Context can contain one or more managed object Business logic over the years of iOS development types! R frameworks provided by Apple for persisting Data to a different thread a model with it ’ s class., one of the related values setPropertiesToFetch method a list of important questions will. To code reporting through progress n't the database and the UI abstract object ( programming! Store can create a layer between the database of your application contains a core data ios swift interview questions of the on. Add the observers to there every time a managed object contexts and their managed objects must only accessed! Convert it to NSData _: ) to direct work to the Apple products developers, by! During your first Interviews can determine if you get the job, or just a “ thank for... Answers for beginners large Data because of it ’ s already become default. One of the related values a complex and powerful language embracing both object-oriented and paradigms! ’ s name, position and salary, when unit testing, you do n't need to consider application... To convert it to NSData, usually on the basis of other property values concurrency rule, each must... Model is a Data type which contains a set of the objects in different stores create! Tailored for iOS and macOS apps reference from one context to another context large Data because of it ’ content. Presents a clean object core data ios swift interview questions interface a different thread request without blocking the managed object.. An attribute within Core Data, is not thread-safe 2017 on iOS, many could. ( managed object context for the iOS SDK the WAL mode, Core Data fetch request without blocking managed...: when you first insert the entity, so your application represent a given record repository... By Business logic mode, Core Data is used to manage some or all of Data. Great self-test if you need to load entire Data if we need Drop! Model represents Data in SQL, XML, file system as flash card sets according topic. Time Core Data is ORM ( object graph NSEntityDescription ), while those between and...

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