1. Difference between unowned and weak

The difference between unowned and weak is that weak is declared as an Optional while unowned is not. By declaring it weak you get to handle the case that it might be nil inside the closure at some point. If you try to access an unowned variable that happens to be nil, it will crash the whole program. So only use unowned when you are positive that variable will always be around while the closure is around

example :

-  Not optional 

UIView.animate(withDuration: 0.1) { [unowned self] in
    // test here                
}

-  if condition is optional 

UIView.animate(withDuration: 0.1) { [weak self] in
    // test here                
}

source: https://stackoverflow.com/a/24320474/8366535

 2. Reason: image not found

This how to fixing if you found this error in debug area

dyld: Library not loaded: @rpath/GTMSessionFetcher.framework/GTMSessionFetcher

  Referenced from: /Users/user/Library/Developer/Xcode/DerivedData/app-fdbtvslxujpubfeopseixqoigrp/Build/Products/Debug-iphonesimulator/Common.framework/Common

  Reason: image not found

(lldb) 

Solution:

In the terminal, do a pod update -> pod install -> clean and run project
this work in my case .

Or try 

delete DrivedData  and build again

Source: https://github.com/Alamofire/Alamofire/issues/3051#issuecomment-580003683


 3. UIView Auto constrain inside stackView

In condition have a view inside stack view and have stack view inside view like this

stackView -> View ->  Stackview

so the solution is  

1. set constraint 2nd stackview top, landing, trailing and bottom to view

2. set view height Grether than equal with minimum constant

 4. Error "Return from initializer without initializing all stored properties"

If found error "Return from initializer without initializing all stored properties"

Solution In my case is, Error in code below:

public struct CardObject: Codable {
  public let productName: String?
  public let cardName: String? 
}

that because model use let constant,  for fixing change "let" to "var"

public struct CardObject: Codable {
  public var productName: String?
  public var cardName: String? 
}

 5. Error " cannot convert value of type 'Int' to expected argument type 'DispatchTimeInterval' "

If found this error in jenkins and run unit test in xcode "Success"

error like this  cannot convert value of type 'Int' to expected argument type 'DispatchTimeInterval'

 so solution update your pods and build again for Unit test

 6. Overriding declarations in extensions is not supported

If  you found an error  like that image above, the solution is to move your code in class where from

don't use extensions  extension make you have error, here i,e

From  

public extension viewController {
  public func testClass() {}
  public func testClassTwo() {}
}

To like this

public class viewController {
    override func viewDidLoad() {
        super.viewDidLoad()
    }

    public func testClass() {}
    public func testClassTwo() {}
}

 7. Error CryptoSwift need update pods version

[!] `CryptoSwift` requires CocoaPods version `>= 1.9.1`, which is not satisfied by your current version, `1.8.3`.

solution  is update pods version in terminal

$sudo gem install cocoapods

 8. Error requires CocoaPods version in Jenkins

Update gemfile and Gemfile.lock

$bundle update




Or you can use this too

$bundle install --path vendor/bundle

This in gemfile.lock before and after update

Change in info.plist bundel version string (short) to higer  version

example from this (2.0.0) to (2.0.1)