Quick Answer: What Is Strong In Swift?

What is strong reference in Swift?

Strong Reference Cycle.

In essence, strong references are used to describe the relationship between objects.

When an object has a strong reference to another object, this creates a retain cycle that prevents the object that is being referenced from being deallocated and increases the retain count to 1..

What is strong and weak in IOS?

strong is the default. An object remains “alive” as long as there is a strong pointer to it. weak specifies a reference that does not keep the referenced object alive. A weak reference is set to nil when there are no strong references to the object.

What is ARC in Swift?

Swift uses Automatic Reference Counting (ARC) to track and manage your app’s memory usage. … ARC automatically frees up the memory used by class instances when those instances are no longer needed.

Why we use lazy in Swift?

Lazy properties are also useful when the initial value for a property requires complex or computationally expensive setup that shouldn’t be performed unless or until it’s needed. The example below uses a lazy stored property to avoid unnecessary initialization of a complex class.

What is the difference between weak and unowned?

The first difference you need to know about is that an unowned reference is always expected to have a value. … When that happens, the reference is set to nil . Because a weak reference can be set to nil , it is always declared as an optional. That is the second difference between weak and unowned references.

What is atomic and Nonatomic in iOS?

Atomic means only one thread accesses the variable (static type). Atomic is thread-safe, but it is slow. Nonatomic means multiple threads access the variable (dynamic type). Nonatomic is thread-unsafe, but it is fast.

What is strong and weak in Swift?

April 21, 2018. A strong reference means that you want to “own” the object you are referencing with this property/variable. In contrast, with a weak reference you signify that you don’t want to have control over the object’s lifetime.

What are strong and weak references?

Strong References: This is the default type/class of Reference Object. Any object which has an active strong reference are not eligible for garbage collection. … Weak References: Weak Reference Objects are not the default type/class of Reference Object and they should be explicitly specified while using them.

What is unowned self in Swift?

The most common place you’ll see unowned variables is with closures that declare [unowned self] – this means “I want to reference self inside this closure but I don’t want to own it.” Why unowned rather than weak ? Both would work, but let’s face it: if self is nil inside a closure, something has gone wrong!

What is a lazy VAR in Swift?

Swift has a mechanism built right into the language that enables just-in-time calculation of expensive work, and it is called a lazy variable. These variables are created using a function you specify only when that variable is first requested.

What is computed property in Swift?

Swift offers us two kinds of property: a stored property is one that saves a value for use later, and a computed property is one that runs some code in order to calculate the value. … The computed property returns a string based on joining the four stored properties into a sentence.

What is memory leak iOS?

A memory leak in iOS is when an amount of allocated space in memory cannot be deallocated due to retain cycles. Since Swift uses Automatic Reference Counting (ARC), a retain cycle occurs when two or more objects hold strong references to each other.

How many references can there be to a single object?

Three: the original reference, and one reference each for a formal and an acutal parameter. d. There can be any number of references, held in any number of variables and parameters (as long as they are of the correct type.)

What is weak var Swift?

A weak reference is just a pointer to an object that doesn’t protect the object from being deallocated by ARC. … In Swift, all weak references are non-constant Optionals (think var vs. let ) because the reference can and will be mutated to nil when there is no longer anything holding a strong reference to it.

Why delegates are weak in Swift?

With using lazy keyword we are not initializing delegate which means there is no memory leak right now. Let’s break that. Object will be created and there will be memory leak. … Therefore, if the object conforming to the protocol needs to be stored in a weak property then the protocol must be a class-only protocol.

Why is IBOutlet weak?

In Mac development an IBOutlet is usually a weak reference: if you have a subclass of NSViewController only the top-level view will be retained and when you dealloc the controller all its subviews and outlets are freed automatically. UiViewController use Key Value Coding to set the outlets using strong references.

What is a weak reference Java?

A Weak reference is a reference that does not protect a referenced object from collection by GC. i.e. garbage collects when no Strong or Soft refs. A Phantom reference is a reference to an object is phantomly referenced after it has been finalized, but before its allocated memory has been reclaimed.

What is a Java reference?

A reference is an address that indicates where an object’s variables and methods are stored. You aren’t actually using objects when you assign an object to a variable or pass an object to a method as an argument. You aren’t even using copies of the objects. Instead, you’re using references to those objects.

What is closure in Swift?

Closures are self-contained blocks of functionality that can be passed around and used in your code. Closures in Swift are similar to blocks in C and Objective-C and to lambdas in other programming languages. … Nested functions are closures that have a name and can capture values from their enclosing function.

Why is delegate weak in iOS?

For delegation patters in iOS, the delegated object is the parent, because there is no need for the delegate caller to exist without the delegated object. … When you define a delegate object as property, it’s used a weak reference in the object it is defined in(lets say A, i.e. the delegate object is a property of A).

What is retain count in Swift?

Retain Count represents number of owners for a particular object. It is zero till object does not have any owners. Increase in one ownership claim will cause retain count to increase by 1 and decrease will cause it to decrement by 1. Example: – Class A object is created using alloc/init and retain count is 1.