iphone - IBOutlet and IBAction - Stack Overflow

 

ios ibaction iboutlet

IBAction, IBOutlet, and IBOutlet Collection play important roles in development, on both the compiler level and human level. As Objective-C continues to rapidly evolve as a platform, it is likely that they may someday be as completely vestigial as the wings of flightless birds or eyes of ushealthlife.mld: Jul 07, Aug 23,  · What is an IBOutletCollection in iOS?? When we try to create a new IBOutlet or new IBAction, a third option shows up named IBOutletCollection. I always wondered what it Author: Abhimuralidharan. Jun 14,  · An IBOutlet (Interface Builder outlet) is a variable which is a reference to a UI component. An IBAction (Interface Builder action) is a function which is called when a specific user interaction occurs. You want work to happen when you hit a butto.


IBAction / IBOutlet / IBOutletCollection - NSHipster


Elements in a storyboard are linked to source code. In a storyboard, a scene represents one screen of content and typically one view controller. A view controller manages a single content view with its hierarchy of subviews.

You define the behavior of your view controllers in code by creating and implementing custom view controller subclasses. You can then create a connection between those classes and scenes in your storyboard to get the behavior you defined in code and the user interface you defined in your storyboard.

Xcode already created one such class that you looked at earlier, ViewController. At runtime, ios ibaction iboutlet storyboard creates an instance of ViewControllerios ibaction iboutlet, your custom view controller subclass.

Although the scene is connected to ViewController. To define interaction in your app, your view controller source code needs to be able to communicate with the views in your storyboard.

You do this by defining additional connections—called outlets and actions—between the views in the storyboard and the view controller source code files. Outlets provide a way to reference interface objects—the objects you added to your storyboard—from source code files. To create an outlet, Control-drag from a particular object in your storyboard to a view controller file. This operation creates a property for the object in your view controller file, ios ibaction iboutlet, which lets you access and manipulate that object from code at runtime.

To connect the text field to the ViewController. Click the Assistant button in the Xcode toolbar near the top right corner of Xcode to open the assistant editor, ios ibaction iboutlet. If you want more space to work, collapse the project navigator and utility area by clicking the Navigator and Utilities buttons in the Xcode toolbar. You can also collapse the outline view.

In ViewController, ios ibaction iboutlet. You just added a comment to your source code. Specifically, the comment you added indicates that this is the section of your code that lists properties. Control-drag from the text field on your canvas to the code display in the editor on the right, stopping the drag at the line below the comment you just added in ViewController.

In the dialog that appears, ios ibaction iboutlet, for Name, type nameTextField. Leave the rest of the options as they are. Xcode adds the necessary code to ViewController. The weak keyword indicates that the reference does not prevent the system from deallocating the referenced object. Weak references help prevent reference cycles; however, to keep the object alive and in memory you need to make sure some ios ibaction iboutlet part of your app has a strong reference to the object.

A superview maintains a strong reference to all of its subviews. As long as the superview remains alive and in memory, all of the subviews remain alive as well. Similarly, the view controller has a strong reference to its content view—keeping the entire view hierarchy alive and in memory. The rest of the declaration defines an implicitly unwrapped optional variable of type UITextField named nameTextField.

Pay careful attention to the exclamation point at the ios ibaction iboutlet of the type declaration. This exclamation point indicates that the type is an implicitly unwrapped optional, which is an optional type that will always have a value after it is first set. When you access an implicitly unwrapped optional, ios ibaction iboutlet system assumes it has a valid value and automatically unwraps it for you.

Now, ios ibaction iboutlet the label to your code in the same way you connected the text field. To connect the label to the ViewController.

Control-drag from the label on your canvas to the code display in the editor on the right, stopping the drag at the line just below your nameTextField property in ViewController.

In the dialog that appears, for Name, type mealNameLabel, ios ibaction iboutlet. Again, Xcode adds the necessary code to ViewController. You only need an outlet to an interface object if you plan to either access a value from the interface object or modify the interface object in your code.

Outlets let you refer to your interface elements in code, but you still need a way to respond whenever the user interacts with the elements. That is, the flow of the app is determined by events: system events and user actions.

The user performs actions in the interface that trigger events in the app. Because the user, rather than the developer, is in control of when certain pieces of the app code get executed, you ios ibaction iboutlet to identify exactly which actions a user can perform and what happens in response to those actions.

You can define an action method to accomplish anything from manipulating a piece of data to updating the user interface. You use actions to drive the flow of your app in response to user or system events. You create an action the same way you create an outlet: Control-drag from a particular object in your storyboard to a view controller file. This operation creates a method in your view controller file that gets triggered when a user interacts with the object that the action method is attached to.

Start by creating a simple action that sets the label to Default Text whenever the user taps the Set Default Text button. Control-drag from the Set Default Label Text button on your ios ibaction iboutlet to the code display in the editor on the right, stopping the drag at the line below the comment you just added in ViewController. You may have noticed that the value of the Type field defaults to AnyObject.

In Swift, AnyObject is a type used to describe an object that can belong to any class. Specifying the type of this action method to be UIButton means that only button objects can connect to this action. The sender parameter refers to the object that was responsible for triggering the action—in this case, a button. The IBAction attribute indicates that the ios ibaction iboutlet is an action that you can connect to from your storyboard in Interface Builder.

Right now, the method declaration is empty. The code to reset the value of the label is quite simple, ios ibaction iboutlet. To implement the label reset action in the ViewController code. Checkpoint: Test your changes by running the simulator. You should see the change in your user interface. The ios ibaction iboutlet you just implemented is an example of the target-action pattern in iOS app design. Target-action is a design pattern where one object sends a message to another object when a specific event occurs.

The target is ViewController where the action method is defined. The system sends the message by calling the action method on the target and passing in the sender object. The sender is usually a control—such as a button, slider, ios ibaction iboutlet, or switch—that can trigger an event in response to user interaction such as a tap, drag, or value change.

At this point, users can reset the meal name label to a ios ibaction iboutlet value, but you really want to let users enter their own meal names using the text field. When you work with accepting user input from a text field, you need some help from a text field delegate.

A delegate is an object that acts on behalf of, or in coordination with, another object. The delegating object—in this case, the text field—keeps a reference to the other object—the delegate—and at the appropriate time, the delegating object sends a message to the delegate. The message tells the delegate about an event that the delegating object is ios ibaction iboutlet to handle or has just handled. The delegate may respond by for example, updating the appearance or state of itself or of ios ibaction iboutlet objects in the app, or returning a value that affects how an impending event is handled.

The delegate can use this information to save or clear data at the right time, ios ibaction iboutlet, dismiss the keyboard, ios ibaction iboutlet, and so on. Any object can serve as a delegate for another object as long as it conforms to the appropriate protocol. It is very common to make a view controller the delegate for objects that it manages. You adopt a protocol by listing it as part of the class declaration line.

If the assistant editor is open, return to the standard editor by clicking the Standard button. Expand the project navigator and utility area by clicking the Navigator and Utilities buttons in the Xcode toolbar. In the project navigator, select ViewController. By adopting the UITextFieldDelegate protocol, you tell the compiler that the ViewController ios ibaction iboutlet can act as a valid text field delegate. To set the ViewController object as the delegate of its ios ibaction iboutlet property.

The template implementation of this method includes a comment. Below the super. When ios ibaction iboutlet ViewController instance is loaded, it sets itself as the delegate of its nameTextField property.

Just implement the ones you need to get the behaviors you desire. When the user taps a text field, it automatically becomes the first responder. In an app, the first responder is an object that is first on the line for receiving many kinds of app events, including key events, motion events, and action messages, among others.

In other words, many of the events generated by the user are initially routed to the first responder. As a result of the text field becoming the first responder, iOS displays the keyboard and begins an editing session for that text field. What a user types using that keyboard gets inserted into the text field. When a user wants to finish editing the text field, the text field needs to resign its first-responder status. Because the text field will no longer be the active object in the app, ios ibaction iboutlet, events need to get routed to a more appropriate object.

You need to specify that the text field should resign its first-responder status when the user taps a button to end editing in the ios ibaction iboutlet field. This comment is used to organize your code and to help you and anybody else who reads your code navigate through it.

The Functions menu lets you jump to a section in your code quickly. You can click on one of the section titles to jump to that section in the file. Try typing the second line instead of just copying and pasting. When Xcode brings up the list of potential completions, scroll through the list until you find the one you want and then press Return.

Xcode inserts the whole line for you. This method returns a Boolean value that indicates whether the system should process the press of the Return key. In this case, you always want to respond to the user pressing the Return key, so just return true.

 

Using IBAction and IBOutlet in Xcode for Swift

 

ios ibaction iboutlet

 

IBAction, IBOutlet, and IBOutlet Collection play important roles in development, on both the compiler level and human level. As Objective-C continues to rapidly evolve as a platform, it is likely that they may someday be as completely vestigial as the wings of flightless birds or eyes of ushealthlife.mld: Jul 07, Actions and outlets in iOS are referred to as ibActions and ibOutlets respectively, where ib stands for interface builder. These are related to the UI elements and we will explore them after knowing visually how to implement them. You need to use IBOutlet and IBAction if you are using interface builder (hence the IB prefix) for your GUI components. IBOutlet is needed to associate properties in your application with components in IB, and IBAction is used to allow your methods to be associated with actions in IB. For example, suppose you define a button and label in IB.