Continuing from Part 1
Welcome back to our series on frequently asked questions in iOS interviews! In the first part of this series, we covered a range of easy questions that are frequently asked in iOS interviews. In this second and final part, we will delve into more advanced topics such as networking, security, and app performance optimization. Whether you are a seasoned iOS developer looking to brush up on your skills or a newcomer to the field looking to prepare for your first job interview, this article is sure to have something for you. So let’s dive in and continue our journey towards acing that iOS interview!
Questions & Answers
Question: Difference between frame vs bounds in iOS
Answer: a view’s frame specifies it’s position and size inside of it’s parent view’s coordinate system. While a view’s bounds specifies it’s position and size inside of it’s own coordinate system.
Question: Static vs Dynamic Method Dispatch
Answer: Method dispatch refers to the operation a program uses to determine which method’s implementation should be executed when a method is called. Static dispatch is determined at compile time, while dynamic dispatch is determined at runtime. Structs are statically dispatched, while classes are dynamically dispatched.
Question: What are closures?
Answer: self contained blocks of code-functionality that can be passed around and used in your code. They are essentially headless or anonymous functions without the func keyword, that are capable of causing retain cycles due to their ability to capture strong references to objects.
Question: What’s a retain cycle?
Answer: a retain cycle is a situation where two or more objects hold strong references to each other, creating a cycle of ownership that prevents the objects from being deallocated from memory. This can lead to a leak of memory resources, as the objects will continue to occupy space in memory even when they are no longer needed. It is important to be mindful of the relationships between objects and to use weak references appropriately. In Swift, the weak or unowned keyword can be used to indicate that a reference should not contribute to the reference count of an object, thereby preventing retain cycles.
Question: What’s Escaping vs non-escaping?
Answer: One important aspect of working with closures in Swift is the concept of escaping versus non-escaping closures. An escaping closure is a closure that is called after the function it was passed to returns, while a non-escaping closure is called within the function it was passed to.
The difference between escaping and non-escaping closures is important because it affects how the closure is stored and used. Non-escaping closures are easier to work with because they are executed immediately and do not need to be stored for later execution. Escaping closures, on the other hand, are stored and executed at a later time, which means they need to be captured and retained in memory until they are called. A good example of escaping closure is usually call back network request to perform some sort of asynchronous task.
Question: What’s a singleton?
Answer: Singletons are objects that should only ever be created once, then shared everywhere they need to be used. They are a common design pattern in iOS development and even Apple’s platform code: FileManager, UserDefaults, UIApplication etc all use Singleton Design pattern.
Question: What is Dependency Injection?
Answer: Dependency injection is a fancy name for a simple thing: when we create an object in our app, we want to provide it with all the necessary data it needs to work. Dependency Injection is a software design pattern in which an object receives other instances that it depends on. It’s a commonly used technique that allows reusing code, insert mocked data, and simplify testing.
Question: What is the difference between a synchronous and an asynchronous operation in iOS?
Answer: A synchronous operation is one that is executed in a blocking manner, meaning that the calling thread will wait for the operation to complete before continuing. An asynchronous operation, on the other hand, is executed in a non-blocking manner, allowing the calling thread to continue without waiting for the operation to complete. In iOS development, asynchronous operations are often used to perform long-running tasks, such as downloading data from the internet, without blocking the main thread and affecting the user experience.
Question: What is the difference between a delegate and a data source in iOS?
Answer: A delegate is an object that acts on behalf of another object, handling specific events or tasks. A data source, on the other hand, is an object that provides data to another object, typically for display in a user interface. In iOS development, delegate and data source patterns are often used to decouple the implementation of a class from the behavior or data that it needs. For example, a table view might use a delegate to handle user interactions, such as selection or scrolling, and a data source to provide the data for the table view to display.
Question: What is the Model-View-Controller (MVC) design pattern, and how is it used in iOS development?
Answer: The MVC design pattern is a way of organizing code in a software application. It divides the application into three main components: the model, the view, and the controller. The model represents the data and business logic of the application, the view represents the user interface, and the controller acts as a mediator between the model and the view, controlling the flow of data between them. This design pattern is commonly used in iOS development to create a clear separation of concerns and make it easier to develop, maintain, and test the application.
Question: What is delegation in iOS, and how is it used?
Answer: Delegation is a design pattern in which one object (the delegate) acts on behalf of another object (the sender) by handling specific tasks or events. This pattern is commonly used in iOS development to allow one object to communicate with or control another object without having to know the details of its internal implementation. For example, a view controller might use delegation to handle the events generated by a text field, without having to know how the text field is implemented.
Conclusion
In this article, we have covered a range of advanced topics that are commonly asked in iOS interviews, from memory management to design patterns and a host of other topics. We hope that this article has provided you with the knowledge and confidence you need to ace your iOS interview and succeed in your career as an iOS developer.
Remember, it is always a good idea to prepare for your interview by reviewing the basics and staying up-to-date with the latest developments in the iOS ecosystem. Whether you are a seasoned developer or a newcomer to the field, there is always more to learn and improve upon. With the right mindset and a willingness to continually learn and grow, you will be well on your way to success in the exciting world of iOS development. ✌️