1.  if you found an error like "Use of undeclared type 'UIColor' " 

error Use of undeclared type 'UIColor', or  Use of undeclared type 'UICgrect' all about 'UI'
a solution is : maybe you forgot "import UIKit"

2.  Set logo Uiimage in Navigation item title

this example code for set navigation item change from title to image / your logo
//------------------------------------------------------------------------
func setUpNavigationBarTitleImage() {
        let navController = navigationController!
        let image = UIImage(named: "logo.png")!
        let imageView = UIImageView(image: image)
        let bannerWidth = navController.navigationBar.frame.size.width
        let bannerHeight = navController.navigationBar.frame.size.height
       
        imageView.frame = CGRect(x: 0, y: 0, width: bannerWidth, height: bannerHeight)
        imageView.contentMode = .scaleAspectFit
        imageView.center = navController.navigationBar.center
       
        navigationItem.titleView = imageView

    }
//------------------------------------------------------------------------

and then set in viewdidload.

//------------------------------------------------------------------------
override func viewDidLoad() {
        super.viewDidLoad()
       
       setUpNavigationBarTitleImage()
        
    }

//------------------------------------------------------------------------
3.  function " handler: " in UIAlertController must you know

handler as parameter,  you can use like an example below

//------------------------------------------------------------------------
let ac = UIAlertController(title: "Open page…", message: nil, preferredStyle: .actionSheet)
  ac.addAction(UIAlertAction(title: "apple.com", style: .default, handler: openPage))
....
func openPage(action: UIAlertAction) {
    let url = URL(string: "https://" + action.title!)!
    webView.load(URLRequest(url: url))
}
//------------------------------------------------------------------------

This method takes one parameter, which is the UIAlertAction object that was selected by the user. Obviously, it won't be called if Cancel was tapped, because that had a nil handler rather than openPage.


4. Remove separator last line use viewForFooterInSection

tableview just remove separator last line or last index
//------------------------------------------------------------------------
public func tableView(_ tableView: UITableView, viewForFooterInSection section: Int) -> UIView? {
        return UIView(frame: .zero)
    }

//------------------------------------------------------------------------
https://stackoverflow.com/questions/44223810/last-static-cell-separator-line-appears-after-reloading-table-view

5. Height tableview dynamic by indexPath row

Is there any way by which I can get row height of each row in a UITableView. I have a UITableView which contains data which is dynamic, u can use in numberOfRowsInSection for dynamic and static use in viewdidload.

heightManual.constant = tableView.contentSize.height

6. How add separator to string at every 3 characters in swift?
}

ex:
let char = "5551190003451"

let account = char.inserting(separator: "-", every: 3)

print(account)      // Result -> "555-119-000-345-1"

//------------------------------------------------------------------------

link : https://stackoverflow.com/a/34454633/8366535


7. String Attribute  Swift 4.2

link : https://stackoverflow.com/a/32269975/8366535

Quick Reference

// create attributed string
let myString = "Swift Attributed String"
let myAttribute = [ NSAttributedString.Key.foregroundColor: UIColor.blue ]
let myAttrString = NSAttributedString(string: myString, attributes: myAttribute) 

// set attributed text on a UILabel
myLabel.attributedText = myAttrString

let myAttribute = [ NSAttributedString.Key.foregroundColor: UIColor.blue ]

let myAttribute = [ NSAttributedString.Key.backgroundColor: UIColor.yellow ]

let myAttribute = [ NSAttributedString.Key.font: UIFont(name: "Chalkduster", size: 18.0)! ]

let myAttribute = [ NSAttributedString.Key.underlineStyle: NSUnderlineStyle.single.rawValue ]

let myShadow = NSShadow()
myShadow.shadowBlurRadius = 3
myShadow.shadowOffset = CGSize(width: 3, height: 3)
myShadow.shadowColor = UIColor.gray

let myAttribute = [ NSAttributedString.Key.shadow: myShadow ]

---

Attributes

• key name: NSAttributedString.Key.font, value: a UIFont
• key name: NSAttributedString.Key.foregroundColor, value: a UIColor
• key name: NSAttributedString.Key.link, value: an NSURL or NSString

• key name: NSAttributedString.Key.myName, value: some Type.
  if you make an extension:

  extension NSAttributedString.Key {
      static let myName = NSAttributedString.Key(rawValue: "myCustomAttributeKey")
  }

Creating attributes in Swift

// single attributes declared one at a time
let singleAttribute1 = [ NSAttributedString.Key.foregroundColor: UIColor.green ]
let singleAttribute2 = [ NSAttributedString.Key.backgroundColor: UIColor.yellow ]
let singleAttribute3 = [ NSAttributedString.Key.underlineStyle: NSUnderlineStyle.double.rawValue ]

// multiple attributes declared at once
let multipleAttributes: [NSAttributedString.Key : Any] = [
    NSAttributedString.Key.foregroundColor: UIColor.green,
    NSAttributedString.Key.backgroundColor: UIColor.yellow,
    NSAttributedString.Key.underlineStyle: NSUnderlineStyle.double.rawValue ]

// custom attribute
let customAttribute = [ NSAttributedString.Key.myName: "Some value" ]

var multipleAttributes = [NSAttributedString.Key : Any]()
multipleAttributes[NSAttributedString.Key.foregroundColor] = UIColor.green
multipleAttributes[NSAttributedString.Key.backgroundColor] = UIColor.yellow
multipleAttributes[NSAttributedString.Key.underlineStyle] = NSUnderlineStyle.double.rawValue

Attributed Strings

// Initialize with a string only
let attrString1 = NSAttributedString(string: "Hello.")

// Initialize with a string and inline attribute(s)
let attrString2 = NSAttributedString(string: "Hello.", attributes: [NSAttributedString.Key.myName: "A value"])

// Initialize with a string and separately declared attribute(s)
let myAttributes1 = [ NSAttributedString.Key.foregroundColor: UIColor.green ]
let attrString3 = NSAttributedString(string: "Hello.", attributes: myAttributes1)

// Create a blank attributed string
let mutableAttrString1 = NSMutableAttributedString()

// Initialize with a string only
let mutableAttrString2 = NSMutableAttributedString(string: "Hello.")

// Initialize with a string and inline attribute(s)
let mutableAttrString3 = NSMutableAttributedString(string: "Hello.", attributes: [NSAttributedString.Key.myName: "A value"])

// Initialize with a string and separately declared attribute(s)
let myAttributes2 = [ NSAttributedString.Key.foregroundColor: UIColor.green ]
let mutableAttrString4 = NSMutableAttributedString(string: "Hello.", attributes: myAttributes2)

Changing an Attributed String

let myAttribute = [ NSAttributedString.Key.font: UIFont(name: "Chalkduster", size: 18.0)! ]
let myString = NSMutableAttributedString(string: "Swift", attributes: myAttribute )

textView.attributedText = myString

let attrString = NSAttributedString(string: " Attributed Strings")
myString.append(attrString)

var myRange = NSRange(location: 17, length: 7) // range starting at location 17 with a lenth of 7: "Strings"
myString.addAttribute(NSAttributedString.Key.foregroundColor, value: UIColor.red, range: myRange)

myRange = NSRange(location: 3, length: 17)
let anotherAttribute = [ NSAttributedString.Key.backgroundColor: UIColor.yellow ]
myString.addAttributes(anotherAttribute, range: myRange)

8. Int To Date

Link: https://stackoverflow.com/questions/39934057/convert-date-to-integer-in-swift
Link: https://blog.apoorvmote.com/convert-date-to-string-vice-versa-in-swift/
Check Int to Date : https://www.epochconverter.com/
Date Helper: https://github.com/mikaelbo/AFDateHelper

Date to Int

// using current date and time as an example
let someDate = Date()

// convert Date to TimeInterval (typealias for Double)
let timeInterval = someDate.timeIntervalSince1970

// convert to Integer
let myInt = Int(timeInterval)

Int to Date

ex:

let myInt = 1556334047174

// convert Int to Double
let timeInterval = Double(myInt)

// create NSDate from Double (NSTimeInterval)
let myNSDate = Date(timeIntervalSince1970: timeInterval)

I could have also used timeIntervalSinceReferenceDate instead of timeIntervalSince1970 as long as I was consistent. This is assuming that the time interval is in seconds. Note that Java uses milliseconds.

OR use this func:

ex:

let myInt = 1556334047174
getDateFromStamp(myInt)
func getDateFromStamp(timeInterval:Int) -> String{
        let date = NSDate(timeIntervalSince1970: TimeInterval(timeInterval / 1000))
        let dateFormatter = DateFormatter()
        dateFormatter.dateFormat = "EEEE, MMM dd, yyyy - HH:mm"
        let dateString = dateFormatter.string(from: date as Date)
        return dateString
    }

9. Remove string <b> and </b> "Bold" from Html code

Swift  Remove  character from string,  example:

//------------------------------------------------------------------------

let str = "<b>loream ipsum</b> dolor"

print(removeStrChar(str)) //  loream ipsum dolor


func removeStrChar(_ str: String) -> String {
        let removeStr = str.replace(string: "<b>", replacement: "")
        let removeStr2 = removeStr.replace(string: "</b>", replacement: "")
        return removeStr2
    }

//------------------------------------------------------------------------