Tag: garbage collection

Does copy increase retain count?

No, a copied object will have a retain count of 1

, just like a newly initialized object. I highly recommend you read the Memory Management Guide if you wish to learn more. If you’re new to iOS development, the iOS App Programming Guide should be read first, and is a great use of your time.

What is a difference between copy and retain?

Retain increases the retain count of an object by 1 and takes ownership of an object. Whereas copy will copy the data present in the memory location and will assign it to the variable

so in the case of copy you are first copying the data from a location assign it to the variable which increases the retain count.

What is retain count?

The retainCount is

the number of ownership claims there are outstanding on the object

. You take ownership of an object if you create it using a method whose name begins with “alloc” or “new” or contains “copy” (for example, alloc, newObject, or mutableCopy), or if you send it a retain message.

What is retain count in Swift?

How to check reference count Swift?

You can always check the reference count of a variable by

using the CFGetRetainCount function

. Note: Reference counting is done only to manage memory for reference types (e.g., classes and closures).

What is difference between assign and retain?

Assign creates a reference from one object to another without increasing the source’s retain count. Retain creates a reference from one object to another and increases the retain count of the source object.

What is the difference between Copy and Link?

“Copy” will create a new product with the same info as the original, in the new category and independent of the original product. “Link” will create a reference from the new category to the original product, so you can make future changes once (in the master category) and have it up to date in all places.

How do I remove Viewcontroller from memory?

You can’t remove a view controller from within itself (i.e. viewDidDisappear) – what you need to do is to

remove all references to it

, at which point ARC will deallocate it.

What is a retain cycle?

What are retain cycles and memory leaks? 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

.

What is retain in iOS?

You send an object a retain message when you want to prevent it from being deallocated until you have finished using it

. An object is deallocated automatically when its reference count reaches 0 . retain messages increment the reference count, and release messages decrement it.

How do you find the retain count in an ARC?

You will need to

click on the info descriptor (the ‘i’ next to Allocation in the left pane) and click on “Record Reference Counts”

. You can then profile your app and do a search for the specific class you’re looking to inspect.

How do you avoid reference cycle?

To break the strong reference cycle between an Account instance and a Plan instance, we

declare the account property of the Plan class as weak

. Remember that this has a few consequences. We need to declare the account property as a variable property and it needs to be of an optional type.

What is strong weak and unowned in Swift?

Swift provides two ways to resolve strong reference cycles when you work with properties of class type: weak references and unowned references. Weak and unowned references

enable one instance in a reference cycle to refer to the other instance without keeping a strong hold on it

.

Is ARC a garbage collection?

ARC differs from tracing garbage collection in that there is no background process that deallocates the objects asynchronously at runtime

. Unlike tracing garbage collection, ARC does not handle reference cycles automatically.

Is reference counting garbage collection?

Garbage collection

As a collection algorithm, reference counting tracks, for each object, a count of the number of references to it held by other objects

. If an object’s reference count reaches zero, the object has become inaccessible, and can be destroyed.

What is the difference between frames and bounds?

Frame is used by the view’s parent view to place it inside the parent view. Bounds is used by the view itself to place it’s own content

(like a scroll view does while scrolling).

What is atomic and nonatomic?

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 atomic and Nonatomic in Swift?

Is a hard link just a copy?

Are hard links copies?

This content has not changed. This hard link is

duplicate copy of the original file

, a shortcut to the file. Editing it will make changes to the file. The hard link acts like the copy.

Where do copied links go?

Add a copied URL

After you copy a URL, it saves to

your device’s clipboard

. To add or paste the URL: Touch and hold the text field. Tap Paste.

What is memory leak in IOS?

As per Apple, a memory leak is:

Memory that was allocated at some point, but was never released and is no longer referenced by your app

. Since there are no references to it, there’s now no way to release it and the memory can’t be used again.

How do I remove Viewcontroller?

What is Viewdidload in Swift?

A Boolean value indicating whether the view is currently loaded into memory

. Creates the view that the controller manages. Loads the view controller’s view if it’s not loaded yet.

What is capture list in closures?

Capture lists:

The list of values that you want to remain unchanged at the time the closure is created

. Capturing values: If you use external values inside your closure, Swift stores them alongside the closure. This way they persist even when the external part of the code no longer exists.

What is weak self in closure?

In Swift, [weak self]

prevents closures from causing memory leaks in your application

. This is because when you use [weak self], you tell the compiler to create a weak reference to self. In other words, the ARC can release self from memory when necessary.

What is the difference between weak and unowned?

What is weak and strong property 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. Follow this answer to receive notifications.

What is Nsobject in iOS?

What is lazy property in Swift?

What is strong in Swift?

In Swift, a strong reference is

the default, for variables, properties, constants, passing into functions (depending on what you do with it), and for closures

. With ARC, an instance is only deallocated when its retain count is zero. A strong reference increases the retain count by 1, a weak reference does not.

How can you avoid strong reference cycles in a closure?

Why is ARC compile time?

ARC is a compiler feature that provides automatic memory management of Objective-C objects. Instead of you having to remember when to use retain, release, and autorelease,

ARC evaluates the lifetime requirements of your objects and automatically inserts appropriate memory management calls for you at compile time

.

What is a weak VAR in Swift?

Weak References in Swift

Weak References are one solution to retain cycles in Swift.

A weak reference does not increment or decrement the reference count of an object

. Since weak references do not increment the reference count of an object, a weak reference can be nil .

Is Swift garbage collected?

Swift uses a simple garbage collection mechanism

. It’s called ARC (Automatic Reference Counting). This approach is based on tracking the strong references count to an object held by other objects.

What is a memory leak in programming?

In computer science, a memory leak is

a type of resource leak that occurs when a computer program incorrectly manages memory allocations in such a way that memory which is no longer needed is not released

. A memory leak may also happen when an object is stored in memory but cannot be accessed by the running code.