Best iOS Interview Questions And Answers

Swift, a modern programming language, was announced by Apple Inc. in June 2014.

• Fast (static method dispatch)
• Safe (type safe)
• Friendly syntax (more concise than objective-c)

Some key features are unique and powerful: generics, tuples, closures, and type inference are optional.

Swift uses static typing, which can lead to a compiler error. Objective-C uses dynamic typing, which performs type checking at runtime. This means that the code can compile even if it contains errors that prevent the script from working properly.

A function that allows the compiler to automatically set the data type of a variable without setting the data type by looking at the value.

A type that can take any type. It is type safe, which means the compiler will complain at compile time. For example, if you pass a string as a generic type and use it as an integer, a compile-time error occurs. This is good because you can spot errors ahead of time.

In Objective-c, any object can be nil. In Swift, only Optionals can be null.

A protocol is an interface, that is, it contains abstract methods, constants, and variables. Protocols provide shared functionality between classes. You can implement multiple protocols.

In Swift, a constant is a constant and a variable is changed. Volatility is determined when a variable is initialized with a keyword, not a specific data class.

In Objective-C, mutability is limited to specific classes. For example, you must use the NSMutableArray type to be able to resize the array.

Subscripts are shortcuts for accessing member elements of a collection, list, or sequence.

AnyObject does not specify any type, so it will allow you to pass any type, which could lead to a runtime error (which is bad). When you use generics you need to specify the type, so it won't let you pass if you enter the wrong type at compile time (which is good).

Optional is a type that can store a nil value. When it stores a value, it wraps around the value. To enclose a value in an optional parameter, you need to expand it.

Structs are value types and classes are reference types.

Stack and heap of memory

The stack is a simple first-in-first-out (FIFO) memory structure. The stack is always used to store the following two things: the reference portion of local variables and parameters of the reference type, and local variables and method parameters with a value type.

Heap memory contains random non-lined objects stored in memory. The advantage is that it allows objects to be allocated or released in a random order. This will require you to use garbage collector functions to free memory.

The heap stores the following: the contents of reference type objects.

Standalone functions organized in blocks. They can be transferred and nested within each other. You can pass the closure as an argument to a function, or store it as a property of an object.

It is a pointer to any type in object-c. (Like any in Swift) Since it can store any type, there will be no compilation errors and you can convert it to another type later.

This is considered as inaction (no operation). It will simply execute the next instruction. This is not a bug and it will just return nil or 0.

NSArray is used when you don't want to resize or change the data stored in the array. In the NSMutable array, you can add, remove, or change the values ​​in the array.

Compile-time dynamic typing.

By the transition and delegation pattern.

If you use the optional "inout" keyword in a parameter, the original value passed in the parameter will be changed after the function is executed.

func swapTwoInts(_ a: inout Int, _ b: inout Int) {   let temporaryA = a
  a = b
  b = temporaryA
}

This is a framework provided by Apple that deals with multiple threads. It is used when you want to work on an asynchronous job. For example, if you want to fetch data from an API, you can use GCD to perform fetch tasks asynchronously.

With synchronous execution, one task does not start until another completes. When scheduling tasks asynchronously, tasks run concurrently.

weak var name: String?

It is a system in xCode that dynamically calculates the size and position of all views based on the constraints placed on those views.

The proprietary data storage provided by Apple provides persistent storage. It's easy to manage because you can use xcode to change the model name or attributes. It is native so it is very easy to update it.

UIView borders are location (x, y) and width (x, y), but UIView border refers to the supervisor that UIView contains.

A design pattern in programming where you can only use one instance per class. This instance is called a "shared instance".

These are solutions to programming problems like an OOP pattern implemented in the right situation.

• behavioral
• creational
• structural

“A delegate is an object that acts on behalf of or in coordination with another object when that object encounters an event in the program.” © Apple

Categories is an Objective-c term for fast expansion. Basically, you can extend the closure outside of the class. In objective-c you need to name the extension / category.