iOS Actions and Outlets

iOS Actions & Outlets

In iOS Outlets and Actions are basically the property symbol of IBoutlets and IBActions where IB called Interface Builder and the developer should aware that both IBActions and Outlets are the user interface elements.

If you have some knowledge about object oriented programming, we can say that the outlet is basically the reference object and action is the method which is used to perform some type of actions.

Syntax of iOS Actions & Outlets

Following is the syntax of using iOS Actions and Outlets in applications.

@IBOutlet weak var labeltxt: UILabel!

@IBAction func buttonaction(sender: AnyObject) {

labeltxt.text = "Hello"

}

If you observe above syntax we used “@IBOutlet” to add reference of label control and we used “@IBAction” to add button click action to change label control text.

Now we will see how to use iOS Actions and Outlets features in iOS applications with example.

iOS Actions & Outlets Example

To use iOS Actions and Outlets feature in iOS Applications we will create simple application for that open the Xcode Editor from /Applications folder directory. Once we open Xcode the welcome window will open like as shown below. In welcome window click on the second option “Create a new Xcode Project” or choose File à New à Project.

After selecting “Create a new Xcode project” a new window will open in that we need to choose template.

The new Xcode window will contain several built-in app templates to implement common type of iOS apps like page based apps, tab-based apps, games, table-view apps, etc. These templates are having pre-configured interface and source code files. 

For this iOS Actions and Outlets example, we will use most basic template “Single View Application”. To select this one, Go to the iOS section in left side à select Application à In main area of dialog select “Single View Application” and then click on next button like as shown below.

After click Next we will get window like as shown below, in this we need to mention project name and other details for our application.

Product Name: “iOS Actions & Outlets”

The name whatever we enter in Product Name section will be used for the project and app.

Organization Name: “Tutlane”

You can enter the name of your organization or your own name or you can leave it as blank.

Organization Identifier: “com.developersociety”

Enter your organization identifier in case if you don't have any organization identifier enter com.example.

Bundle Identifier: This value will generate automatically based on the values we entered in Product Name and Organization Identifier.

Language: “Swift”

Select language type as “Swift” because we are going to develop applications using swift.

Devices: “Universal”

Choose Devices options as Universal it means that one application is for all apple devices in case if you have any specific requirement to run app only for iPad then you can choose the iPad option to make your application restricted to run only on iPad devices.

Use Core Data: Unselected

This option is used for database operations. In case if you have any database related operations in your application select this option otherwise unselect the option.

Include Unit Tests: Unselected

In case if you need unit tests for your application then select this option otherwise unselect it.

Include UI Tests: Unselected

In case if you need UI tests for your application then select this option otherwise unselect it.

Once you finished entering all the options then click on Next button like as shown below

Once we click on Next button new dialog will open in that we need to select the location to save our project. Once you select the location to save project then click on Create button like as shown below

After click on Create button the Xcode will create and open a new project. In our project Main.storyboard and ViewController.swift are the main files which we used to design app user interface and to maintain source code. 

Main.storyboard - Its visual interface editor and we will use this file to design our app user interface 

ViewController.swift - It contains source code of our application and we use this file to write any code related to our app.

Now in project select Main.storyboard file the Xcode will open visual interface editor like as shown below.

Now select ViewController.Swift file in your project that view will be like as shown below.

Add Controls to StoryBoard File in iOS

Now we will add controls to our application for that open Object Library. The Object Library will appear at the bottom of Xcode in right side. In case if you don't find Object library, click on the button which is at the third position from the left in the library selector bar like as shown below. (Alternatively you can choose View à Utilities à Show Object Library).

As we discussed our user interface will be in Main.storyboard file so open Main.storyboard file. Now in Object library search for the label in Filter field then drag and drop the label into Main.storyboard ViewController same way drag and drop the button control in ViewController like as shown below.

Connect UI Controls to Code

If we want to implement any functionality for UI controls, we need to map UI controls to the code in ViewController.swift.  

Now we will map our controls to ViewController.swift file for that we need to use Assistant editor in Xcode. Open the Xcode editor in assistant mode for that click on the overlap circle button in Xcode toolbar at top right side like as shown below

Now press Ctrl button in keyboard and drag the controls from your canvas to the code display in ViewController.swift file like as shown below.

Once you drag the controls from viewcontroller to code in ViewController.swift file now write code in @IBAction to change the label text when click on button. Once we make required changes our ViewController.swift file should be like as shown below

//  ViewController.swift

//  iOS Actions & Outlets

//

//  Created by Tutlane on 14/08/2016.

//  Copyright © 2016 Tutlane. All rights reserved.

//

import UIKit

class ViewController: UIViewController {

@IBOutlet weak var labeltxt: UILabel!

@IBAction func buttonaction(sender: AnyObject) {

labeltxt.text = "Hello"

}

override func viewDidLoad() {

super.viewDidLoad()

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

}

override func didReceiveMemoryWarning() {

super.didReceiveMemoryWarning()

// Dispose of any resources that can be recreated.

}

}

Now we will run and check the output of application. To run application, select the required simulator (Here we selected iPhone 6s Plus) and click on Play button, located at the top-left corner of the Xcode toolbar like as shown below.

Output of iOS Actions & Outlets App

Following is the result of iOS Actions and Outlets app. Once we run application click on button it will change the label text. The button performs the action for label to change its outlet text.

This is how we can use iOS Actions and Outlets in our swift applications to attach action methods and references to UI controls.