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iOS with Swift Lab Learning Guide: Building an App with Form and Core Data
Learning Outcomes:
Create an IOS app with SWIFT to demonstrate the use of a form whose fields are written to and retrieved from the iOS Core Data framework
Resources:
Big Nerd Ranch Guide
Room Database is an abstraction layer over SQLite for Android devices, providing a more convenient way to persist data locally. In iOS, the equivalent framework for persisting data locally is Core Data, which is provided and managed by Apple itself. Core Data is commonly recommended for storing and accessing structured data in iOS applications.
What is the difference between room and core data in ios
Room and Core Data are both frameworks used to manage the lifecycle of objects in a mobile application, often using SQLite as a local/on-device database
. However, they are designed for different operating systems: Room is for Android, while Core Data is for iOS.Core Data is a powerful and flexible iOS framework that allows storing data in applications and devices. It works with such programming languages as Objective-C and Swift and remains in high demand among iOS developers
. Core Data is a framework for managing an object graph, which is a collection of interconnected objects. The framework is responsible for managing the life cycle of the objects in the object graph. It can optionally persist the object graph to disk and also offers a powerful interface for searching the object graph it manages. Core Data adds a number of other compelling features, such as input validation, data model versioning, and change tracking
.On the other hand, Room is a part of Android's Jetpack suite of libraries and is an abstraction layer over SQLite, providing a more convenient way to persist data locally. It offers compile-time checks of SQL statements and can return RxJava, Flowable and LiveData observables, among other features. However, Room is not available for iOS development
.In terms of comparison, both Room and Core Data are abstractions on top of a data store, but they take very different approaches
. Core Data is often considered to have a steeper learning curve but offers first-party security and reliability
. Some developers also find Core Data to be more memory-efficient
.In conclusion, while Room and Core Data serve similar purposes, they are designed for different platforms and have different features and capabilities. Therefore, the choice between the two would largely depend on the platform (Android or iOS) you are developing for.
Write a fully functional iox xcode app which will take field data from a form and store it into core data
.
. To create a data model, choose File > New > File and select iOS > Core Data > Data Model
.swift
Explainlet managedContext = persistentContainer.viewContext
let entity = NSEntityDescription.entity(forEntityName: "YourEntity", in: managedContext)!
let newObject = NSManagedObject(entity: entity, insertInto: managedContext)
newObject.setValue(inputField.text, forKeyPath: "yourProperty")
do {
try managedContext.save()
} catch let error as NSError {
print("Could not save. \(error), \(error.userInfo)")
}
In this code, persistentContainer is an instance of NSPersistentContainer, which is part of the Core Data stack that Xcode automatically generates for you when you create a new project with Core Data
. YourEntity and yourProperty should be replaced with the name of your Core Data entity and the property you want to set, respectively. inputField.text should be replaced with the text input from your form.swift
let fetchRequest = NSFetchRequest<NSManagedObject>(entityName: "YourEntity")
do {
let objects = try managedContext.fetch(fetchRequest)
// Update your user interface with the fetched objects.
} catch let error as NSError {
print("Could not fetch. \(error), \(error.userInfo)")
}
In this code, YourEntity should be replaced with the name of your Core Data entity.
Please note that this is a simplified overview of the process. Depending on the complexity of your app, you might need to handle errors more robustly, perform more complex queries, manage relationships between objects, etc. For a more detailed guide, you might want to check out some tutorials or documentation on Core Data
.Introduction
In this lab, students will build an iOS application using Swift that demonstrates creating a user interface with a form, and persisting form data using Core Data. Core Data is a framework provided by Apple for managing the model layer of your application in a way that's both efficient and scalable.
Objective
By the end of this lab, students will be able to:
Prerequisites
To participate in this lab, students should:
Tools and Materials Needed
Lab Structure
Section 1: Setting Up the Project
Section 2: Designing the Form Interface
Implementation Instructions for UI Components and Form Design using Storyboard
Below you'll find step-by-step instructions to create a basic form in an iOS application using Swift. You will learn how to implement UI components (UITextField, UILabel, and UIButton), design the form using Storyboard, and use Auto Layout constraints to ensure the form is responsive across different device sizes.
Step 1: Open Xcode and Create a New Project
Step 2: Design the User Interface
Step 3: Configure UI Components
Step 4: Setting Up Auto Layout Constraints
Step 5: Enable Auto Layout and Stack View (Optional)
Step 6: Create Outlets and Actions in the View Controller
class ViewController: UIViewController {
@IBOutlet weak var textField: UITextField!
@IBOutlet weak var label: UILabel!
@IBAction func submitButtonTapped(_ sender: UIButton) {
// Code to handle button tap
}
// Rest of the ViewController class
}
Step 7: Handle the Button Tap to Read Text Field Input
Implement the button action in ViewController.swift.
@IBAction func submitButtonTapped(_ sender: UIButton) {
// Read the text from the textField and set it to the label
label.text = textField.text
}
Step 8: Finalize the Form and Test
By following these steps, you will have created a simple form interface with responsive design using Auto Layout in Storyboard. Remember to save your work frequently and test on various simulators to ensure the layout looks correct on all devices.
Section 3: Implementing the Form Logic
Section 3: Implementing the Form Logic
Understanding the Delegation Pattern for Managing Text Input
The delegation pattern is a core principle in iOS where one object acts on behalf of, or in coordination with, another object. When dealing with text input in UITextField, the delegation pattern allows us to define behaviors for different user actions such as editing began, changed text, and editing ended.
The UITextField has a delegate property that expects an object that conforms to the UITextFieldDelegate protocol. This protocol includes a number of optional methods that you can implement to handle text field events.
Implementing the UITextFieldDelegate Protocols
To use the UITextFieldDelegate protocols, follow these steps:
Step 1: Conform to UITextFieldDelegate
First, indicate that your ViewController conforms to the UITextFieldDelegate protocol. This can be done within the class interface declaration in your ViewController.swift file:
class ViewController: UIViewController, UITextFieldDelegate {
// Rest of the ViewController class
}
Step 2: Assign the Delegate
Next, in your ViewController setup or viewDidLoad method, assign the view controller as the delegate of the UITextField:
override func viewDidLoad() {
super.viewDidLoad()
// Assign the text field's delegate property to self (the view controller)
textField.delegate = self
}
Step 3: Implement Delegate Methods
Implement the needed UITextFieldDelegate methods to handle text input. Commonly used delegate methods include:
func textFieldShouldReturn(_ textField: UITextField) -> Bool {
// Called when the user taps the return key on the keyboard
// Dismiss the keyboard
textField.resignFirstResponder()
// Return false if you do not want the text field to perform default behavior, such as inserting a new line character
return true
}
func textFieldDidBeginEditing(_ textField: UITextField) {
// Called when the text field starts being edited
}
func textFieldDidEndEditing(_ textField: UITextField) {
// Called when the text field resigns first responder status (editing ends)
}
func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
// Called each time the user types or deletes a character
// You can use this to limit the number of characters, restrict input to certain characters, etc.
// Return true to allow the text change or false to prevent it
return true
}
Writing Functions to Handle User Interactions
Apart from handling text field specific interactions, we're also interested in handling general user interactions such as a button tap to save data.
Step 4: Write Action for Button Tap
Within your ViewController, implement the logic for when the button is tapped. Below we assume the button's action is linked to a function named submitButtonTapped:
@IBAction func submitButtonTapped(_ sender: UIButton) {
// Triggered when the user taps the submit button
// Optional: Validate the input text
guard let inputText = textField.text, !inputText.isEmpty else {
// Handle the case where the text field is empty
// Could show an alert or a warning label
return
}
// Use the text to perform an action, such as saving it to a variable or calling another function
// For now, let's just print the text
print("Submitted text: \(inputText)")
// Clear the text field if needed
textField.text = ""
// Dismiss the keyboard if it's still up
textField.resignFirstResponder()
}
This method captures the text in the form's text field when the submit button is tapped, optionally validates the text, and then performs an action with the text.
Remember to wire up this action to your UIButton in the Storyboard by right-clicking the button and dragging to the "Touch Up Inside" event trigger, then selecting submitButtonTapped.
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