iOS Developer Interview Question and Answers

Welcome to this blog dedicated to iOS developer interviews! Whether you're a beginner or a mid-level developer, this blog is designed to provide you with valuable insights and preparation materials to excel in iOS development interviews.

Here, you'll find a comprehensive collection of short questions and answers specifically tailored for both Swift and Objective-C, the primary programming languages used in iOS app development.  We understand that interviews can be nerve-wracking, especially when it comes to technical discussions, but our blog goal is to equip you with the necessary tools and knowledge to boost your confidence and ace those interviews.

Whether you're just starting your journey as an iOS developer or looking to advance your career, our blog is here to provide you with a valuable resource for interview preparation. Let's enhance your interview performance!

# 1: What is Swift and why is it used for iOS development? 

• Swift is a general-purpose, multi-paradigm, compiled programming language developed by Apple for iOS, iPadOS, macOS, watchOS, tvOS, and Linux. It is designed to be safe, fast, and interactive.

# 2: What is the difference between Swift and Objective-C?

• Swift is a newer programming language that is faster and safer than Objective-C.
• It also has a more modern syntax, while Objective-C has a more verbose syntax.
• Swift is easier to read and write than Objective-C, and it also provides safer and faster code execution. 
• Swift also has a more concise syntax, automatic reference counting, and improved type safety compared to Objective-C. 
• Swift also has improved memory management and eliminates the need for header files.

# 3: What are some benefits of using Swift over other programming languages? 

• Swift is easier to read and write compared to other programming languages. 
• It is safer, with fewer crashes and errors. 
• It is also faster in terms of code execution. 
• Swift also has a more concise syntax, automatic reference counting, and improved type safety compared to other languages.

#4: What is an Optional in Swift?

• An optional in Swift is a type that represents either a value or the absence of a value. It's used to handle cases where a value may be missing or optional. 
• Optionals are declared using a "?" after the type, such as "Int?" for an optional integer.
• You can use the "?" operator to safely unwrap the optional and access its value, or the "if let" or "guard let" statements to handle nil values.

#5: What is a closure in Swift? 

• A closure in Swift is a self-contained block of code that can be passed around and used in your code. 
• Closures can capture values from their surrounding context and can be used as function arguments or stored as properties and can also be returned from functions.

# 6: What is the difference between value types and reference types in Swift?

•  In Swift, value types (structs and enums) are passed by value, meaning that a copy of the value is made and passed around. 
• Reference types (classes) are passed by reference, meaning that a reference to the same instance is passed around.

#7: What is the difference between a class and a structure in Swift? 

• Classes and structures are similar in that they both allow you to create custom data types in Swift. However, classes support inheritance and reference semantics, while structures support value semantics. 
• This means that when you pass a structure to a function or assign it to a variable, a copy of the structure is created, while with classes, only a reference to the existing instance is passed or assigned.

#8: What is the difference between a delegate and a protocol in Swift?  

• In Swift, a delegate is a design pattern that allows one object to send messages to another object in response to events. 
• Delegation is a way of connecting objects together, allowing one object to delegate responsibility for certain tasks to another object.
• A protocol, on the other hand, is a blueprint of methods, properties, and other requirements that suit a particular task or piece of functionality. 
• The protocol defines what methods or properties should be implemented, but it doesn’t provide the implementation itself.

#9: How can you make an HTTP request in Swift?

• You can make an HTTP request in Swift using various libraries such as the built-in URLSession or third-party libraries such as Alamofire. 
• You can also use the URLRequest class from the Foundation framework to make an HTTP request.

#10: What is the difference between weak and strong references in Swift?

• In Swift, a strong reference means that an object cannot be deallocated as long as there is at least one strong reference to it. 
• A weak reference, on the other hand, does not prevent the object from being deallocated. 
• Weak references are used to break reference cycles and prevent memory leaks.

#11: What is the difference between let and var in Swift?

• In Swift, the "let" keyword is used to declare a constant, meaning that the value of a constant cannot be changed after it is set. 
• The "var" keyword, on the other hand, is used to declare a variable, meaning that the value of a variable can be changed after it is set.

#12: How can you declare a function in Swift?

• In Swift, you can declare a function using the "func" keyword followed by the function name, its parameters, and its return type. 
• For example: 

       func greet(name: String) -> String { 

              return "Hello, (name)!" 

        }

#13: What is the difference between value types and reference types in Swift?  

• In Swift, value types (such as structs and enums) are passed by value, meaning that when you pass a value type to a function or assign it to a variable, a copy of the value is created. 
• On the other hand, reference types (such as classes) are passed by reference, meaning that when you pass a reference type to a function or assign it to a variable, only a reference to the existing instance is passed or assigned, not a new copy of the instance.

#14: What are the control transfer statements in swift?

  

   The control transfer statements in swift are:

• Continue

• Break

• Fallthrough

• Return

#15: How can you make a property optional in Swift?

• An optional in Swift is a type that can hold either a value or no value. Optionals are written by appending a ? to any type:

• Example

           var middleName: String? = "middleName"

• Declaring a question mark "?" in the code can make a property optional.

#16: Why do we use swift? Mention some advantages of Swift?

    A few of the many advantages of using swift are:

• Optional types
• Closures
• Built-in error handling
• Much faster than other languages
• Supports pattern matching

#17: What is benefit of using higher order functions? 

     

    Higher order functions are those in which you can pass a function as an             

    argument and returns a function as a result. 

    There are many benefits to using them, below are few: 

• They provide flexibility but compromises with complexity.
• They are useful in asynchronous communications in which simple functions can’t be used.
• They improve the readability of code and decreases the length of the code.

#18: Explain Enum in Swift?

• An enum in swift is used to defines a common type for a group of related values. It enables you to work with those values in a type-safe way within your code.
• Basically, it is a type that contains a group of various related values under the same umbrella.

#19: What is nil coalescing operator in swift?

• In swift is called nil coalescing operator that finds if optional has no value then it uses a default value.

#20:  What is iOS and what are its key features? 

• iOS is the operating system used by Apple devices such as the iPhone, iPad, and iPod Touch. It is known for its user-friendly interface, security features, and compatibility with a wide range of apps and services.

# 21: What are initialiser in Swift?

• Swift initializer is a special type of method that can be called to create a new instance of a particular type.
• Swift provides a default initializer for any structure or class that provides default values for all of its non-optional properties and does not provide the initializer itself.

#22: What is the difference between an iPhone and an iPad?

• An iPhone is a compact smartphone that is designed to be used primarily with one hand. An iPad is a larger tablet device that is designed for multimedia consumption and productivity.

#23: Explain Deinitializer in Swift programming Language?

• In Swift, a deinitializer is used to free up the resources by deallocates your instance class when they remain no longer useful for you. a dinit keyword is used to represent it. It is only present on class types.

#24: What do you mean by the term “defer”?

• The term “defer” is a keyword that provides a block of code that executes when the execution is leaving the current scope.

#25: What is the difference between nil and None in Swift?

• Usually, there is no difference between nil and None in Swift. nil & .none are the equivalent to each other.

#26: What is an in-out parameter in Swift?

• In-out parameter lets you change the value of a function parameter from within the body of that function.

#27: What is the difference between optional chaining and forced unwrapping in Swift? BEG

• In Swift, both optional chaining and forced unwrapping are used to work with optional values. However, they work in different ways.
• Optional chaining is used to access the value of an optional if it has a value or to return nil if it doesn't. It is performed by placing a question mark after the optional value, followed by the property, method, or subscript that we want to access. If the optional has a value, the access will succeed, and we'll get the value. If the optional is nil, the access will fail, and the entire expression will return nil.
• On the other hand, forced unwrapping is used to extract the value of an optional if we're sure that it has a value. We can use forced unwrapping by placing an exclamation mark after the optional value. If the optional has a value, the exclamation mark will unwrap the value and give us the underlying non-optional value. If the optional is nil, the exclamation mark will cause a runtime error.
• In general, we should avoid forced unwrapping because it can cause runtime errors if the optional is nil. Instead, we should use optional chaining to safely work with optional values.

#28: What is the difference between optional binding and optional chaining in Swift? 

• In Swift, both optional binding and optional chaining are used to work with optional values. However, they work in different ways.
• Optional binding is used to safely unwrap an optional value and assign it to a new constant or variable. We use the if let or guard let syntax to check if the optional has a value, and if it does, we can assign the unwrapped value to a new constant or variable. If the optional is nil, the code inside the if or guard block won't execute. Optional binding is useful when we need to use the unwrapped value multiple times within a block of code.
• On the other hand, optional chaining is used to safely access a property or call a method on an optional value. We use the ? operator to chain the property or method to the optional value. If the optional is nil, the property or method call won't be executed, and the entire expression will evaluate to nil.
• optional binding is used to safely unwrap an optional value and use it within a block of code, while optional chaining is used to safely access a property or call a method on an optional value.

#29: Can you explain any three-shift pattern matching techniques?

• Typecasting Patterns – This pattern allows you to match or cast the types.
• Wildcard Patterns – This pattern matches as well as ignores any kind and type of value.
• Optional Patterns – This pattern is used to match the optional values.

#30: What is tuple? How to create a tuple in Swift ?

• A tuple is used to arrange multiple values in a single compound Value. In tuple, it is not compulsory for value to be of the same type. It can be of any type.
• For an instance, ("company", [1,2,3]) is a tuple having two values: one is string Type, and another one is an Array type.

#31: Can you explain completion handler?

• When our application is making an API call and we are supposed to update the UI to show the data from the API call, then Completion Handler becomes handy and is super convenient.

#32: Distinguish between @synthesize and @dynamic in Objective –C?

• @synthesize – It generates the getter and setter methods for the property.
• @dynamic – It notifies the compiler that the getter and setter are implemented at some other place.

#33: What is the App Store and how does it work?

• The App Store is a digital distribution platform for iOS apps. It allows users to browse and download apps developed by third-party developers or Apple itself. 
• The App Store reviews and approves each app before it is made available to users.

#34: What is a UIViewController in iOS

• A UIViewController is a basic building block of an iOS app. It manages a single screen of content, typically a user interface, and handles user interactions with that content.

#35: What is the difference between a UINavigationController and a UITabBarController in iOS?

• A UINavigationController provides a navigation interface for hierarchical content, allowing the user to navigate back and forth between screens. A UITabBarController provides a tab-based interface for switching between different screens.

#36: What is Auto Layout and how does it work in iOS?

• Auto Layout is a layout system that allows you to create user interfaces that dynamically adapt to different screen sizes and orientations. It uses a set of constraints to define the relationships between elements in a user interface.

#37: What is Core Data and how does it work in iOS? 

• Core Data is a framework that provides an object-oriented model for storing and retrieving data in iOS apps. It provides a powerful and flexible way to manage data, with features such as change tracking, undo/redo, and data validation.

#38: What is the difference between a delegate and a data source in iOS?

• A delegate in iOS is an object that acts on behalf of, or in coordination with, another object. A data source is an object that provides data to another object, typically by implementing methods defined by a protocol.

#39: What is a storyboard in iOS and how does it work?

• A storyboard is a visual representation of the user interface of an iOS app, showing the flow of screens and the relationships between elements on those screens. You can use storyboards to design, prototype, and test your app's user interface.

#40: What is the Model-View-Controller (MVC) design pattern and how is it used in iOS development?

• The Model-View-Controller (MVC) design pattern is a way of organising code into distinct layers to improve the separation of concerns and the maintainability of your code. In iOS development, the Model layer represents data and business logic, the View layer represents the user interface, and the Controller layer acts as an intermediary between the Model and View.

#41: What is a UITableView and how does it work in iOS?

• A UITableView is a scrollable view that displays a list of items, each represented by a single row. You can use a UITableView to display a variety of content, from simple text to complex multimedia.

#42: Explain iOS application states

• Not running – This state means that there is no code that is being executed and the application is completely switched off.
• Inactive – This state means that the application is running in the background foreground and is not receiving any events.
• Active – This state means that the applications are running in the background  foreground and is receiving the events.
• Background – This state means that the application is executing the code in the background.
• Suspended – This state means that the application is in the background and is not executing.

#43: Can you explain the role of the AppDelegate in an iOS project?

• The AppDelegate is a special kind of object in an iOS project that is responsible for managing the lifecycle of the application. It acts as a central hub for the application, handling important events such as application launch, background/foreground transitions, and termination. The AppDelegate is also responsible for setting up the root view controller for the application and for responding to other important application-level events.

#44: What is the difference between push and modal navigation in iOS development? 

• Push navigation is a type of navigation in which a new view controller is pushed onto the stack, and becomes visible to the user. The new view controller covers the current view controller, which is still present in the background. Push navigation is typically used for hierarchical navigation, where the user drills down into deeper levels of detail. Modal navigation, on the other hand, presents a view controller as a modal dialog, which requires the user to take some action before returning to the previous view controller. Modal navigation is typically used for temporary or secondary tasks.

#45: Can you explain the difference between a storyboard and a nib file in iOS development?

• A storyboard is a visual representation of the user interface of an iOS application, showing all of the screens (or scenes) in the application and the transitions between them. A nib file, on the other hand, is a standalone XIB file that contains a single view or interface. Storyboards are a newer feature in iOS development and offer a number of advantages over nib files, including the ability to manage multiple screens in one file and to visually design the transitions between screens.

#46: Can you describe the difference between weak and strong references in iOS development?

• In iOS development, references are used to connect objects in the application. A strong reference is a reference that keeps the referenced object alive as long as the reference itself is alive.
• A weak reference, on the other hand, does not keep the referenced object alive. A weak reference is often used when you have a parent-child relationship between objects, where the parent holds a weak reference to the child, so that when parent deallocated it's child also deallocated.

## Design 

#47: What is the Model-View-Controller (MVC) design pattern and how does it relate to iOS development?

• MVC is a design pattern that separates an application into three components: the model, which represents the data; the view, which presents the data; and the controller, which manages the interaction between the model and view. In iOS development, MVC is used to structure the organization of the code, making it easier to maintain and develop.

#48: What is the Model-View-Controller (MVC) architecture in iOS?

• The Model-View-Controller architecture is a design pattern used in iOS applications to separate an application's data (model), user interface (view), and control logic (controller) into separate components. This separation helps to make the code more modular and easier to maintain.

#49: What are some other popular iOS architecture patterns?

• Some other popular iOS architecture patterns include the Model-View-ViewModel (MVVM) pattern, the Model-View-Presenter (MVP) pattern, and the Clean Architecture pattern.

#50: What is the difference between a delegate and a notification in iOS?

• A delegate is a design pattern in which one object delegates responsibility to another object to perform a task or provide data. 
• A notification is a way for an object to notify other objects that a specific event has occurred. 
• Delegates are usually used for one-to-one communication, while notifications are used for one-to-many communication.

#51: How do you decide when to use Core Data versus SQLite in an iOS application?

• Core Data is a framework provided by Apple that allows you to manage the data model of your application, while SQLite is a database engine that can be used to store and manage data. 
• When deciding between the two, you should consider factors such as the size and complexity of your data, the performance requirements of your application, and the level of control you need over the data storage and retrieval process.

#52: What is the difference between synchronous and asynchronous programming in iOS?

• Synchronous programming is a programming model in which the program waits for an operation to complete before continuing to the next operation, while asynchronous programming is a programming model in which the program continues to execute while an operation is being performed in the background.
•  Asynchronous programming is often used in iOS to prevent the user interface from freezing or becoming unresponsive.

#53: How do you optimize the performance of an iOS application?

• There are several techniques that can be used to optimize the performance of an iOS application, including caching, lazy loading, asynchronous programming, and code profiling. 
• It is also important to minimize the use of resources such as memory and CPU, and to optimize the user interface to ensure that it is responsive and easy to use.

#54: How do you design an iOS application for scalability?

• When designing an iOS application for scalability, you should consider factors such as the size and complexity of the data, the number of users, and the expected growth of the application. 
• You should also design the application to be modular and easily extensible, and use scalable data storage solutions such as cloud storage.

#55: How do you manage dependencies in an iOS project?

• There are several ways to manage dependencies in an iOS project, but one of the most popular is by using a dependency manager such as CocoaPods. CocoaPods is a tool that makes it easy to manage dependencies in an iOS project by providing a central repository of third-party libraries. This makes it easy to integrate these libraries into your project, without having to manually manage them.

#56: Explain the Adapter and Memento Pattern?

• Adapter – It lets the classes with incompatible interfaces to work together and it wraps itself around the object to expose a standard interface to interact with that object.
• Memento – This pattern in iOS is used as a part of state restoration. That is this externalised state can be restored without violating any encapsulation. This pattern is especially used for the archiving in Apple.

#57: What is the difference between a protocol-oriented programming and object-oriented programming in Swift? 

• In OOP, we define classes and use inheritance to create sub-classes, while in POP, we define protocols and use composition to create types that conform to one or more protocols.
• In OOP, we often use base classes to define common behaviour, while in POP, we define protocols that describe behaviour that can be shared by different types.
• In OOP, we often use polymorphism to allow objects of different classes to be treated as instances of a common parent class, while in POP, we use protocol conformance to allow types to be treated as instances of a common protocol.
• OOP is good for modeling complex systems with hierarchies of related classes, while POP is good for building modular and reusable code by composing smaller units of behaviour.

#58: Explain Object oriented programming?

• Object-oriented programming (OOP) is a programming paradigm that is centred around the concept of objects. Objects are instances of classes, which encapsulate data and behaviour. In OOP, we define classes with properties and methods, and use inheritance to create sub-classes with specialized behaviour. OOP is based on four main principles: encapsulation, inheritance, polymorphism, and abstraction. OOP focuses on building hierarchies of related classes, and is good for modeling complex systems.

#59: Explain Protocol oriented programming

• Protocol-oriented programming (POP) is a programming paradigm that is centred around the concept of protocols. Protocols define a set of methods and properties that a type must implement to conform to the protocol. In POP, we define protocols that describe the behaviour that a type must exhibit, and use composition to create types that conform to one or more protocols. POP is based on the principle of composition over inheritance, which means that we prefer to build types by composing smaller units of behaviour, rather than inheriting behaviour from parent classes. POP is good for building modular and reusable code.

## Grand Central Dispatch (GCD) 

#60: What is Grand Central Dispatch?

• Grand Central Dispatch is a low-level framework provided by Apple that allows developers to write concurrent code in a simpler and more efficient way. It provides a way to schedule tasks to run on different threads and processors without the need for manual thread management.

#61: What are the advantages of using GCD?

• GCD provides a simple and easy-to-use API that allows developers to write concurrent code with less overhead than manual thread management. GCD is also designed to take advantage of multiple cores and processors, which can improve the performance of concurrent code. Additionally, GCD provides a number of built-in dispatch queues that can be used to prioritise and manage tasks, as well as the ability to create custom dispatch queues.

#62: What are dispatch queues?

• Dispatch queues are a fundamental concept in GCD. They are responsible for managing the execution of tasks, which are represented as blocks of code. There are two types of dispatch queues: serial and concurrent. Serial queues execute tasks in the order they are added to the queue, while concurrent queues can execute tasks simultaneously.

#63: What is a semaphore?

• A semaphore is a synchronisation primitive that can be used to control access to a shared resource. It works by maintaining a count that can be incremented or decremented. When the count is greater than zero, a thread can access the shared resource. When the count is zero, the thread must wait until another thread releases the semaphore.

#64: What is a barrier?

• A barrier is a special type of block that can be added to a dispatch queue to ensure that all tasks submitted before the barrier have completed before the barrier block is executed. This is useful for synchronizing access to shared resources or ensuring that tasks are executed in a specific order.

#65: How do you handle errors in GCD? 

• GCD provides an error handling mechanism through the use of dispatch group notifications. When a task encounters an error, it can signal the dispatch group using the dispatch_group_notify function. The dispatch group can then execute a block of code to handle the error.

#66: What is dispatch group?

• A dispatch group is a way to group a set of tasks and get notified when they have all completed. This is useful for coordinating multiple asynchronous tasks, such as when you need to wait for a set of network requests to complete before updating the UI.

#67: What is dispatch async?

• A: dispatch_async is a function used to asynchronously dispatch a task to a dispatch queue. It immediately returns control to the caller without waiting for the task to complete.

#68: What is dispatch sync?

• dispatch_sync is a function used to synchronously dispatch a task to a dispatch queue. It waits for the task to complete before returning control to the caller. 
• This can be useful in situations where you need to wait for a task to complete before continuing execution.

#69: How do you create a custom dispatch queue?

• You can create a custom dispatch queue using the dispatch_queue_create function. 
• This function takes two arguments: a label to identify the queue and an optional set of attributes that specify the type of queue (e.g. serial or concurrent).

#70: What is the difference between dispatch_async and dispatch_sync?

• dispatch_async asynchronously dispatches a task to a dispatch queue and immediately returns control to the caller without waiting for the task to complete.
•  dispatch_sync, on the other hand, synchronously dispatches a task to a dispatch queue and waits for the task to complete before returning control to the caller. 
• The choice between these two functions depends on the specific requirements of your application.

## Core Data

#71: What is Core Data? 

• Core Data is a framework provided by Apple that allows developers to manage the storage and retrieval of data in their iOS applications. 
• It provides an object-oriented interface to the underlying data store, making it easier to work with complex data models.

#72: What are the advantages of using Core Data?

• Core Data provides a number of advantages over other data storage technologies. 
• It allows developers to work with complex data models using an object-oriented interface, which can make their code more maintainable and easier to write. 
• Core Data also provides automatic management of relationships between objects, support for versioning and migration of data, and performance optimizations such as faulting and batching.

#73: What is a managed object context?

• A managed object context is an object that represents a scratchpad for working with data in Core Data.
•  It is responsible for managing a collection of managed objects and providing an interface for saving changes to the data store.

#74: What is a managed object model?

• A managed object model is an object that describes the data model used by an application in Core Data. 
• It defines the structure of the data, including the entities, attributes, and relationships between them.

#75: What is a persistent store coordinator? BEG

• A persistent store coordinator is an object that coordinates the interaction between a managed object context and the data store. 
• It is responsible for loading and saving data to and from the data store, and for managing the mapping between the data model and the data store schema.

#76: What is a fetch request?

• A: A fetch request is an object that describes the criteria for retrieving data from a managed object context. 
• It can be used to retrieve a single object or a collection of objects that match specific criteria.

#77: What is faulting?

• Faulting is a performance optimization used by Core Data to improve the performance of fetching data. 
• It works by loading only a subset of the data from the data store, and deferring the loading of additional data until it is actually needed.

#78: What is a relationship in Core Data?

• A relationship is a way to define the association between two entities in Core Data. It can be a one-to-one, one-to-many, or many-to-many relationship, and can be represented as a property on the entity object.

#79: What is versioning and migration in Core Data?

• Versioning and migration are features provided by Core Data that allow developers to evolve the data model over time. 
• Versioning involves creating new versions of the data model as it changes, while migration involves migrating data from one version of the data model to another.

#80: What is a NSFetchedResultsController?

• A NSFetchedResultsController is a class provided by Core Data that simplifies the task of displaying data from a Core Data store in a table view. 
• It automatically manages the results of a fetch request and provides updates to the table view when the data changes.

#81: What is a transient property in Core Data?

• A transient property is a property on a managed object that is not saved to the data store. It is calculated on the fly, usually based on the values of other properties on the object.

## Memory management 

#82: What is memory management in iOS?

• Memory management is the process of allocating and deallocating memory in an iOS application. 
• In iOS, memory management is handled through a technique called Automatic Reference Counting (ARC), which automatically manages the allocation and deallocation of memory for objects in the application.

#83: What is ARC?

• ARC stands for Automatic Reference Counting. It is a memory management technique used in iOS to automatically manage the allocation and deallocation of memory for objects in the application.

#84: How does ARC work?

• ARC works by automatically keeping track of the number of references to an object in the application, and deallocating the object when there are no more references to it.

#85: What is a retain cycle?

• A retain cycle occurs when two or more objects hold strong references to each other, preventing them from being deallocated even if they are no longer needed.

#86: How do you avoid retain cycles?

• To avoid retain cycles, you can use weak references or unowned references to break the strong reference cycle. 
• Weak references do not increase the reference count of an object, so they will not prevent the object from being deallocated. 
• Unowned references are similar to weak references, but assume that the reference will always have a value and will not become nil.

#87: What is a strong reference?

• A strong reference is a reference to an object that increases the reference count of the object, preventing it from being deallocated as long as the reference exists.

#88: What is a weak reference?

• A weak reference is a reference to an object that does not increase the reference count of the object, allowing it to be deallocated if there are no other strong references to it.

#89: What is an unowned reference?

• An unowned reference is a reference to an object that does not increase the reference count of the object, but assumes that the reference will always have a value and will not become nil.

#90: What is a memory leak?

• A memory leak occurs when an object is allocated in memory but is not deallocated when it is no longer needed, causing the application to use more and more memory over time.

#91: How do you avoid memory leaks?

• To avoid memory leaks, you should make sure to release all objects that are no longer needed, and make sure that there are no strong reference cycles that prevent objects from being deallocated.

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