Creating And Using Segue in Xcode

Creating a segue from UI element to another view controller

• To create and use segue first of all we will require two viewcontrollers. And I have created two of them namely ViewController and SecondViewController and both are there in storyboard as well.
• Lets say in our first viewcontroller we add a button from object directory by dragging and dropping uibutton in the viewcontroller, this button will take us from ViewController to SecondViewController.
• In order to that we need to setup a segue and setting up a segue is very easy. All you need to do is just click the button, hold down the control key on keyboard and click and drag and point to the SecondViewController.
• You will see a popup of types of segue, chose Show from the options. It can be change at point of development time if needed later on.
• As soon as you chose Show from the option, you will see that Xcode has drawn a line from ViewController to SecondViewController
• And thats all. If you run your app now click on the button it will take you to the SecondViewController

Segue can be created from one view controller to another without initiating it from any UI Element

• What you need to just click on yellow symbol on top the screen which indicates the "View Controller"

• Hold down the control key and drag aero to the SecondViewController and chose type of segue. Now this segue links ViewController to SecondViewController

• Now your question might be "how do I trigger it when I press the button ? "

• In order to use this segue you will need to give it a identifier, go to atribute inspector and keep segue selected and give a name to it. I have given goToSecondScreen.

• Now we need to link the button via IBAction, we can call it buttonPressed.

• Now all we have to say that

    performSegue(withIdentifie: "goToSecondScreen", sender : self)
  

Why need identifier for segues

• Actually we can create multiple segues from single view controller to multiple view controllers.
• We can trigger the other segue from other button on single view controller to some other view controller.
• Since identifier is the string, we have to make sure that we use it exaclty with casing to completely identical to how we names it in atribute inspector

Passing data from one view controller to another using a segue

• Lets consider what user does on first screen will determine the what will apear on second screen.

• Lets take TextField on first screen ViewController and Label on second screen SecondViewController. We are going to ask user to enter some data on first screen and we will pass it to the second screen to display as result.

• I have connected TextField to ViewController and named it textField and Label to SecondViewController and named it label.

• Now override a method prepare for segue as below

    override prepare (for segue: UIStoryboardSegue, sender: Any?){
        if segue.indentifier == "goToSecondScreen" {
    
        }
    }
  

• Now lets create a prperty in SecondViewController called textPassedOver.

        var textPassedOver : String?
  

• Now we have to grab the reference of SecondViewController and assign value to it from textField

        let destinationVC - segue.destination as! SecondViewController
        destinationVC.textPassedOver textField.text
  

• Now lets set textPassedOver value to label in SecondViewController.

• And its working.

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License

Copyright 2018 Ankit Kumar

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

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