Lecture Mobile Application Development (119310)

iOS Development - Framework Basics Part II

Agenda

• Properties in Swift
• Protocols in Swift
• More UIKit
  • UITableViewController
    • UITableViewDelegate Protocol
    • UITableViewDataSource Protocol
  • UITableView
  • UITableViewCell

Properties

• Properties in Swift are like member variables with a getter and setter method in Java
• Swift Properties combine Objective-C’s instance variables and properties in one
• Properties can be constant, variable or computed

Properties

• Properties can define a getter and a setter

Properties Assignment

• Please conduct the Properties Assignment and
  • Create a class Person with three Properties one of them has a getter and setter
  • Learn working with Properties and Strings

Protocols in Swift

• A Protocol is in Swift what an Interface is in Java
• It defines a number of requirements that need to be fulfilled by the implementing classes
  • Property requirements - defines Properties that need to be implemented
  • Method requirements - defines Methods that need to be implemented

Protocols in Swift

• Protocols are defined very similar to classes and structures
• To implement a Protocol in a class you declare it like this:

protocol SomeProtocol {
    // protocol definition goes here
}

class SomeClass: SomeSuperClass, FirstProtocol, SomeProtocol {
    // class definition goes here
}

Protocols in Swift

• Property requirements are declared as variable properties and indicate if they are gettable or settable:

protocol SomeProtocol {

    // a settable Property must be implemented using 
    // var in the implementing class
    var mustBeSettable: Int { get set } 

    // a only gettable Property should be implented using let
    var doesNotNeedToBeSettable: Int { get }

}

Protocols in Swift

• Method requirements are declared like this (like a normal method declaration just without curly braces and implementation):

protocol RandomNumberGenerator {

    func random() -> Double

}

Protocol Assignment

• Please conduct the Protocol Assignment and
  • Extend your Person class with an initializer
  • Create a protocol and implement it in the Person class

UITableViewController

• UIKit class to create lists
  • Similar to ListActivity on Android
• Contains a UITableView to show items in a list
  • Similar to the ListView on Android
• Makes use of the Delegate pattern by 
implementing, e.g. following Protocols
  • UITableViewDelegate
  • UITableViewDataSource
    • Similiar to the ListAdapter on Android

UITableViewDelegate

• The UITableViewDelegate Protocol defines methods that are to be implemented in order to for example:
  • Manage and handle selections
  • Configure Rows, e.g. the height of a row
  • Modifying Header and Footer of Sections
  • Managing TableView highlighting
  • Editing, Copy/Paste and reordering TableRows

UITableViewDelegate

• Example:
  • To handle row selection, override the following method of the UITableViewDelegate Protocol in the UITableViewController:

 override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        print("Selected row \(indexPath.item)")
    }

• Parameters:
  • tableView: the selected TableView (relevant only, if multiple Tables are handled by this class)
  • indexPath: the index of the selected row. The item property contains an int with the row number

UITableViewDataSource

• The UITableViewDataSource Protocol mediates between the Data Model and the TableView
• Works similar to the ListAdapter on Android and defines a number of methods that the UITableViewController implements in order to fill the Table with content, e.g. methods to
  • Get the number of sections in a table
  • Get the number of rows in a section
  • Get the cell for a certain row

UITableViewDataSource

• Example methods implemented in the UITableViewController:

// Override to define the number of sections for the table
override func numberOfSections(in tableView: UITableView) -> Int {
        // #warning Incomplete implementation, return the number of sections
        return 1
    }

// Override to define the number of rows in each section 
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        // #warning Incomplete implementation, return the number of rows
        return shoppingList.count
    }

// Override to define the cell for a given row
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "reuseIdentifier", for: indexPath)

        // Configure the cell...
        
        cell.textLabel?.text = shoppingList[indexPath.item]

        return cell
    }

UITableView

• The UITableView defines the visible list that is controlled by the UITableViewController
• Inherits from UIScrollView
• Can have one of two styles
  • UITableViewStylePlain
  • UITableViewStyleGrouped
• Each row in the UITableView is defined by a UITableViewCell

UITableViewCell

• The UITableViewCell defines the content of the cells that appear in a UITableView
• Inherits from UIView
• Has a predefined textLabel, a detailTextLabel and an imageView Property
• Has a „Reuse Identifier“ to save resources when rendering
• Supports different Cell-Styles
  • Basic
  • Right Detail
  • Left Detail
  • Subtitle

TableView Assignment

• Conduct the TableView Assignment and
  • Create a small shoppinglist app with a TableView that contains the shopping items
  • When one of the items is selected, a second view is shown with the name of the selected item

References

• iOS Dev Center: developer.apple.com
• iOS Reference Library: http://developer.apple.com/library/ios/navigation/