How to add tolerance to Timers in Swift?

March 8, 2019March 8, 2019 ~ Renukha ~ Leave a comment

Tolerance indicates the amount of time after the scheduled fire date, the timer may get fired. The timer may get fired at any time between the scheduled fire date and scheduled fire date + tolerance. Providing a tolerance value will enhance the system responsiveness and increased power savings. Adding tolerance to Swift timers neither cause timer to fire early nor it will allow timer to drift.The system may also add additional delay to timers even if tolerance property is set.

//Timer Tolerance in Swift


timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(self.printMessage), userInfo: timerContext, repeats: true)
timer.tolerance = 2

//Timer Tolerance in Swift

timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(self.printMessage), userInfo: timerContext, repeats: true)

timer.tolerance = 2

Example code snippet using Swift playground.

How to use userInfo parameter in Swift Timers?

March 8, 2019March 8, 2019 ~ Renukha ~ Leave a comment

userInfo parameter in Timers can be used to send additional information about the context in which the timer is used. The information sent is in the form of dictionary as key-value pair and it can be extracted in the selector method that gets executed once the timer gets fired.

//userInfo parameter in Timer


 let timerContext = ["blog" : "Nutcrackerz", "timer" : "Non-repeating"]
 timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(self.printMessage), userInfo: timerContext, repeats: false)

//userInfo parameter in Timer

let timerContext = ["blog" : "Nutcrackerz", "timer" : "Non-repeating"]

timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(self.printMessage), userInfo: timerContext, repeats: false)

Example code snippet from Playground :

Non-repeating timer in Swift

March 8, 2019March 8, 2019 ~ Renukha ~ Leave a comment

Creating a non-repeating timer is simple with the following code:

//Non-repeating Timer in Swift


let timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(self.printMessage), userInfo: nil, repeats: false)

//Non-repeating Timer in Swift

let timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(self.printMessage), userInfo: nil, repeats: false)

timerInterval denotes the number of seconds between the firings of timer.
target denotes the object to which send a message specified by selector.
selector denotes the message to sent to the target after the timer gets fired.
UserInfo can be used to send additional information about timer event in a dictionary format.
repeats denotes whether a timer is repeating or non-repeating. If it is set to true, the timer reschedules itself after getting fired automatically until it is manually invalidated and if it is set to false, the timer fires once and gets invalidated automatically.

Repeating Timer in Swift

March 8, 2019March 8, 2019 ~ Renukha ~ Leave a comment

Creating a repeating timer is simple with the following code.

//Repeating timer in Swift


let timer = Timer.scheduledTimer(timeInterval: 0.5, target: self, selector: #selector(self.printMessage), userInfo: nil, repeats: true)

//Repeating timer in Swift

let timer = Timer.scheduledTimer(timeInterval: 0.5, target: self, selector: #selector(self.printMessage), userInfo: nil, repeats: true)

timerInterval denotes the number of seconds between the firings of timer.
target denotes the object to which send a message specified by selector.
selector denotes the message to sent to the target after the timer gets fired.
UserInfo can be used to send additional information about timer event in a dictionary format.
repeats denotes whether a timer is repeating or non-repeating. If it is set to true, the timer reschedules itself after getting fired automatically until it is manually invalidated and if it is set to false, the timer fires once and gets invalidated automatically.

Timer Class in Swift

March 8, 2019March 8, 2019 ~ Renukha ~ Leave a comment

Swift provides a Timer class which provides a timer that fires after certain time has elapsed sending a specified message to the target object. Timer is not a real time mechanism. They work in conjunction with runloops. The actual time at which the timer fires can be significantly later. Timers can be repeating and non-repeating.

//Repeating Timer in Swift

let timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(self.printMessage), userInfo: nil, repeats: true)

//Repeating Timer in Swift

let timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(self.printMessage), userInfo: nil, repeats: true)

//Non-repeating timer in Swift


let timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(self.printMessage), userInfo: nil, repeats: false)

//Non-repeating timer in Swift

let timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(self.printMessage), userInfo: nil, repeats: false)

How to programatically create a activity indicator in iOS using Swift?

November 4, 2018November 4, 2018 ~ Renukha ~ Leave a comment

The following code creates a activity indicator programatically.

//Programatically creating activity indicator
import UIKit
class ViewController: UIViewController {
    
 let activityIndicator = UIActivityIndicatorView(style: .whiteLarge)
 var timer = Timer()
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        startLoadingSpinner()
        timer = Timer.scheduledTimer(timeInterval: 10, target: self, selector: #selector(stopLoadingSpinner), userInfo: nil, repeats: false)
    }
    func startLoadingSpinner(){
        activityIndicator.frame = self.view.frame
        activityIndicator.center = self.view.center
        activityIndicator.backgroundColor = .blue
        activityIndicator.alpha = 0.8
        activityIndicator.color = .white
        activityIndicator.isHidden = false
        activityIndicator.startAnimating()
        activityIndicator.hidesWhenStopped = true
        self.view.addSubview(activityIndicator)
    }
    @objc func stopLoadingSpinner() {
        self.activityIndicator.stopAnimating()
    }
 }

//Programatically creating activity indicator

import UIKit

class ViewController: UIViewController {

let activityIndicator = UIActivityIndicatorView(style: .whiteLarge)

var timer = Timer()

override func viewDidLoad() {

super.viewDidLoad()

// Do any additional setup after loading the view, typically from a nib.

startLoadingSpinner()

timer = Timer.scheduledTimer(timeInterval: 10, target: self, selector: #selector(stopLoadingSpinner), userInfo: nil, repeats: false)

}

func startLoadingSpinner(){

activityIndicator.frame = self.view.frame

activityIndicator.center = self.view.center

activityIndicator.backgroundColor = .blue

activityIndicator.alpha = 0.8

activityIndicator.color = .white

activityIndicator.isHidden = false

activityIndicator.startAnimating()

activityIndicator.hidesWhenStopped = true

self.view.addSubview(activityIndicator)

}

@objc func stopLoadingSpinner() {

self.activityIndicator.stopAnimating()

}

What do you mean by a literal value ?

November 4, 2018November 4, 2018 ~ Renukha ~ Leave a comment

A literal value is a value that appears directly in the source code. When we specify a literal value for a constant or variable, Swift compiler can automatically detect the type of constant or variable.

//Examples for literal values

var name: String = "Sujatha"
var counter: Int = 0
var height: Double = 125.67

//Examples for literal values

var name: String = "Sujatha"

var counter: Int = 0

var height: Double = 125.67

How to automatically return focus to the cell at last focused indexpath in collectionView?

November 4, 2018November 4, 2018 ~ Renukha ~ Leave a comment

remembersLastFocusedIndexPath

The above boolean property when set to true allows as to return focus to the last collection view cell which was focused before the focus left the collection view. When focus returns to the collection view, the last focused collection view cell will automatically gain focus. By default, this property is set to false.

//Automatically return focus to collectionView cell

var collectionView = UICollectionView()
collectionView.remembersLastFocusedIndexPath = true

//Automatically return focus to collectionView cell

var collectionView = UICollectionView()

collectionView.remembersLastFocusedIndexPath = true

How to automatically return focus to the cell at last focused indexpath in tableView?

November 4, 2018November 4, 2018 ~ Renukha ~ Leave a comment

remembersLastFocusedIndexPath

The above boolean property when set to true allows the focus to return to the tableview cell which was focused before the focus left the tableview. When the focus returns to the tableview, the last focused indexpath of the tableview cell will automatically gain focus. By default, this property is set to false.

//Automatically set focus to last focused cell

var tableView = UITableView()
tableView.remembersLastFocusedIndexPath = true

//Automatically set focus to last focused cell

var tableView = UITableView()

tableView.remembersLastFocusedIndexPath = true

Swift: How ARC works?

September 17, 2018November 4, 2018 ~ Renukha ~ Leave a comment

Whenever we create a new class instance, ARC allocates a chunk of memory to store information about that Class instance. The information stored includes the type of the instance and stored properties associated with that instance. When the instance is no longer needed, ARC frees up the memory so that it can be used for other purposes. ARC keeps track of all the variables, constants and properties which refer to that particular class instance. ARC will not deallocate an instance as long as any one active reference to that instance exists.