//---------- 3.1 Variable ------------------------
var age: Int
- Unlike most of OO, for exampe, in Jave like public int age = 3
var age: Int
do {
print(age)
} catch {
print("never reach here")
}
- the above code will not run
- compiling error: constant 'age' used before being initialized
- modify it by var age:Int = 3
//---------- 3.2 func ------------------------
// --- syntax-1 ---
// declare a func
func div1(a:Int, b: Int) -> Int {
return a /b
}
// call it
let result1 = div1(a:10, b:2)
print(result1)
// --- syntax-2 using underscore ---
// declare a func
func div2(_ a:Int, _ b: Int) -> Int {
return a /b
}
// call it
let result2 = div2(10,2) // classic look
print(result2)
//---------- 3.3.1 class basic-----------------
// lab in Xcode, add a label and button, connect to the view controller
// label name is msg
// outside class ViewController, define a class and init the properties
class Dog{
var name: String = ""
var weight: Int = 0
}
// in the handler for the button, add the code as below
let dog1 = Dog() // create an instance
dog1.name = "Tairo" // set properties
dog1.weight = 32
// output the data
self.msg.text = " \(dog1.name) , \(String(dog1.weight))"
//---------- 3.3.2 class inheritance -----------------
In the following apple link, you'll find the demo
class MediaItem {
var name: String
init(name: String) {
self.name = name
}
}
class Movie: MediaItem {
var director: String
init(name: String, director: String) {
self.director = director
super.init(name: name)
}
}
class Song: MediaItem {
var artist: String
init(name: String, artist: String) {
self.artist = artist
super.init(name: name)
}
}
let library = [
Movie(name: "Casablanca", director: "Michael Curtiz"),
Song(name: "Blue Suede Shoes", artist: "Elvis Presley"),
Movie(name: "Citizen Kane", director: "Orson Welles"),
Song(name: "The One And Only", artist: "Chesney Hawkes"),
Song(name: "Never Gonna Give You Up", artist: "Rick Astley")
]
notes:
* class Movie and Song are inherited from MediaItem.
* All the classes use method init.
* When creating a instance, key word new is not used.
* and, its init method is used.
*The type of library is [AnyObject].
comments:
1. There is no lab here.
2. Lab will be demo in 3.5.4 Optional for type cast.
3. Here, it shows a model style in swift.
4. The swift model class code can be in a different file.
5. iOS uses MVC design pattern. It is a dialect.
//---------- 3.4 Any -----------------
class Product{} // define a class
let p1 = new Product() // create an instance
let a: [Any] = [1, 0.99, "hello", true, p1]
//---------- 3.5 Optional --------------
- To being able to understand some code is important.
- Sometimes, those code are provided, and you have to modify them.
- In Swift, optional concept is quite unique.
- There are two main types - variable with nil value, variable type convertion.
- The related understanding helps.
- Most times, in the Xcode editor, some warning or error icons show up, you can click the fix icons to modify the code
- 3.5.1 unwrap and test nil
* When some variable can not be empty, use optional.
* Unwrap it, if the assignment is good, use the unwrapped data.
* if it is bad, nothing happens.
* test in Xcode - one label and one button
let theUrl: String? = "https://xcloud.com/yz"
//let theUrl: String? = nil
if let temp = theUrl { // unwrap and test nil
print(theUrl)
print(temp)
self.result.text = theUrl
} else {
print(theUrl)
print("because of nil, no update the label")
}
test result with data
- wrapped data: Optional("http://xcloud/yz")
- unwrapped data: http://xcloud/yz
- the unwrapped data is used.
test result without data
- wrapped data: nil
- Nothing happens.
- 3.5.2 Unconditional Unwrapping, ! operator
When you’re certain that an instance of Optional contains a value,
you can unconditionally unwrap the value by using the forced unwrap operator (postfix !).
let name: String! = "John Doe"
self.result.text = name
You can use it directly.
- 3.5.3 Optional chain
class Residence{
var numOfRooms = 1
}
class Person { // Class Person uses class Residence
var residence: Residence?
}
class ViewController: UIViewController {
@IBOutlet weak var result: UILabel!
@IBAction func test(_ sender: Any) {
let johnResidence = Residence()
johnResidence.numOfRooms = 4
let john = Person()
john.residence = johnResidence // comment out this to test nil
if let roomCount = john.residence?.numOfRooms { // optional chain to test nil for residence
self.result.text = String(roomCount) // if success, retrieve data
} else {
print("Unable to retrieve the number of rooms") // if fail, no data retrival
}
}
...
}
- 3.5.4 Optional for type cast as? as!
In 3.3.2 class inheritance, there are 3 classes
- super class: MediaItem
- child class: Movie, song
then, create a constant library: [MediaItem]
The following code is to use the above setup to demo optioanl cast
for item in library {
if let movie = item as? Movie {
print("Movie: \(movie.name), dir. \(movie.director)")
} else if let song = item as? Song {
print("Song: \(song.name), by \(song.artist)")
}
}
* iterate each item in the array
* downcast item from MediaItem to Movie
* if succeed, assign it
* if fail, do not assign
* the same for Type song
lab:
* create a iOS project, in the storyboard, add a label, and a button
* connect them to the files.
* In ViewController.swift, ouside class ViewController,
add code for class MeiaItem, Movie, Song
* in the button's event handler method, add code as below:
class MediaItem{...}
class Movie: MediaItem{...}
class Song: MediaItem{...}
class ViewControler...{
...
@IBAction func test(_ sender: Any){
let library = [
Movie(name: "...", director: "..."),
Song(name: "...", artist: "...),
...]
for item in library {
if let movie = item as? Movie {
print("Movie: \(movie.name), dir. \(movie.director)")
} else if let song = item as? Song {
print("Song: \(song.name), by \(song.artist)")
}
}
* the result is in the debug area.
* for-in loop is used to use test this scenario for querying data with different child types.
* to see the part in the middle of a chain can be casted or not.
class ViewController: UIViewController, UITableViewDataSource {
func tableView(_ tableView: UITableView,
numberOfRowsInSection section: Int) -> Int {
return 15
}
func tableView(_ tableView: UITableView,
cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = UITableViewCell()
cell.textLabel?.text = "row \(indexPath.row)"
return cell
}
-- step 4 contents in a cell
-- step 4.1 imageView object
* prepare one image in 3 different sizes
myImage.png 50 * 50
myImage@2x.png 100 * 100
myImage@3x.png 150 * 150
* add them to the project
- in the project navigator, open Assets.xcassets
- click plus icon, click New Image Set
- Drag these 3 images from the finder onto the target locations
- name the data set to myImage
* render it by code
no work in storyboard
- in ViewController, method cellForRowAt
- after a cell is created, add code as below:
cell.imageView?.image = UIImage(named: "myImage")
* test
For the cell in each row, the image is on the left.
-- step 4.2 accessoryType object
cell.accessoryType = .disclosureIndicator //go to its detail screen
-- step 4.3 detailTextLabel object
cell.detailTextLabel?.text = "data for detailTextLabel" // below the line for textLabel
-- test: you can each cell display as below
image icon text navigation icon
detail text
-- step 5 section, indexPath's property
-- step 5.1 numberOfSections
* implementing a table view data source method(not required)
* if it is not implemented, the default is 1.
* in ViewController.swift, inside the class, type the method name, the code intelliscence will complete the coding.
* modify as: return 3
* test it to see 3 sections.
-- step 5.2 numberOfRowsInSection
* implementing a table view data source method(required)
* modify as below:
switch section {
case 0:
return 5
case 1:
return 2
case 3:
return 3
default:
return 0
*test
-- step 5.3 cellForRowAt
* implementing a table view data source method(required)
* modify as below:
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "cell1", for: indexPath)
switch indexPath.section {
case 0:
cell.imageView?.image = UIImage(named: "myImage")
cell.textLabel?.text = "row \(indexPath.row)"
cell.accessoryType = .disclosureIndicator
cell.detailTextLabel?.text = "detailTextLabel for section 1"
case 1: ....
case 2: ....
default:
cell.textLabel?.text = "error xyz"
}
return cell
}
* test
-- step 5.4 titleForHeaderInSection
* implementing a table view data source method(required)
* modify as below:
switch section {
case 0:
return "Section 1"
case 1:
return "Section 2"
case 3:
return "section 3"
default:
return nil
*test
class ViewController....
var breakfastMenu = [
["name": "oatmeal, eggs, coffee", "price": 12.50],
["name": "toast, fruits, tea", "price": 10.50],
["name": "French toast, scramlbe eggs, coffee", "price": 14.50],
["name": "pancake, porch eggs, coffee", "price": 13.50],
["name": "oatmeal, coffee", "price": 9.50],
]
var lunchMenu = [
["name": "Salad, coffee", "price": 10.50],
["name": "burger", "price": 11.50],
["name": "French chicken", "price": 15.50]
]
var dinnerMenu = [
["name": "Salmon", "price": 15.50],
["name": "clam chowder", "price": 12.50],
["name": "Onion soup", "price": 8.50]
]
-- method numberOfRowsInSection, using data as below:
switch section {
case 0:
return breakfastMenu.count
case 1:
return lunchMenu.count
case 2:
return dinnerMenu.count
....
-- method cellForRowAt, using data as below
switch indexPath.section {
case 0:
let name1 = breakfastMenu[indexPath.row]["name"] as! String
row is for specific table view section for the view
row is also for the corresponding data array.
cell.textLabel?.text = name1
...
let price1 = breakfastMenu[indexPath.row]["price"] as! Double
cell.detailTextLabel?.text = String(price1)
case 1:
// lunchMenu
case 2:
// dinnerMenu
print("You select section \(indexPath.section), row \(indexPath.row)")
import UIKit
class ViewController: UIViewController,UITableViewDataSource {
// 1. data ---------------------------------------
let amTasks = ["check weather", "plan todo", "walk dogs"]
let pmTasks = ["do yard work", "study"]
let eveningTasks = ["watch TV"]
// 2. data source methods -------------------------
func numberOfSections(in tableView: UITableView) -> Int {
return 3
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "cell1", for: indexPath)
switch indexPath.section {
case 0:
cell.textLabel?.text = amTasks[indexPath.row]
case 1:
cell.textLabel?.text = pmTasks[indexPath.row]
case 2:
cell.textLabel?.text = eveningTasks[indexPath.row]
default:
cell.textLabel?.text = "error in cellForRowAt"
}
return cell
}
// not required
func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
switch section {
case 0:
return "Morning Task"
case 1:
return "Afternoon Tasks"
case 2:
return "Evening Tasks"
default:
return nil
}
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
switch section {
case 0:
return amTasks.count
case 1:
return pmTasks.count
case 2:
return eveningTasks.count
default:
return 0
}
}
// 3. UIViewController methods --------------------
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.
}
}
The above is the setup for ALL the following labs.
// --------------- code is as below: ------------
func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {
guard editingStyle == .delete else { return }
print("-----delete ------")
switch indexPath.section {
case 0:
amTasks.remove(at:indexPath.row)
case 1:
pmTasks.remove(at:indexPath.row)
case 2:
eveningTasks.remove(at:indexPath.row)
default:
print("error in remove a row")
}
tableView.deleteRows(at: [indexPath], with: .automatic)
}
// code as below
override func viewDidLoad() {
super.viewDidLoad()
self.navigationController?.navigationBar.barTintColor = UIColor.green
self.title = "My Todolist"
let addbutton = UIBarButtonItem(barButtonSystemItem: .add, target: self, action: #selector(addRow))
self.navigationItem.rightBarButtonItem = addbutton
}
@objc func addRow(){
// 1 get a new row from a user's input
// 1.1 create an alert
let alert = UIAlertController(title: "enter a new task info, 0-based",
message: "task§ion_no&row_no",
preferredStyle: .alert)
// 1.2 add a UITextField
alert.addTextField { (taskField: UITextField) in
taskField.placeholder = "ig. cook&1&1 for pm and 2nd row"
}
// 1.3 add a UIAlertAction
alert.addAction(UIAlertAction(title: "OK", style: .default,
handler: {(action:UIAlertAction) in
if let taskField = alert.textFields?.first {
if taskField.text == "" {
print("You have to enter a task")
} else {
print("task is \(taskField.text ?? "new task")")
// step 2: process the input data - task description, insert location within the same scope
self.insertOneRow(inputRowData: taskField.text!)
}
}
})
)
self.present(alert, animated: true, completion: nil)
}
func insertOneRow(inputRowData: String){
// step 2.1: parse the input data
print("inputRowData = \(inputRowData)")
let inArray = inputRowData.split(separator: "&")
let task = inArray[0]
let sectionNo = Int(inArray[1])
let rowNo = Int(inArray[2])
print("task = \(task)")
print("sectionNo = \(sectionNo ?? 0)")
print("rowNo = \(rowNo ?? 0)")
// step 2.2: updata data
switch sectionNo {
case 0:
amTasks.insert(String(task), at: rowNo!)
print(amTasks)
case 1:
pmTasks.insert(String(task), at: rowNo!)
print(pmTasks)
case 2:
eveningTasks.insert(String(task), at: rowNo!)
print(eveningTasks)
default:
print("error in updata data")
}
// step 2.3: refresh view
tableView.reloadData()
}
// call save for adding a row
alert.addAction(...
....
self.insertOneRow(....)
self.save()
)
// call save for deleting a row
// in the method for commit
// after remove method
self.save()
// call load
// add at the end.
self.load()
func save(){
UserDefaults.standard.set(eveningTasks, forKey: "eveTasks")
UserDefaults.standard.synchronize()
}
func load(){
if let loadData = UserDefaults.standard.value(forKey: "eveTasks")
as? [String] {
eveningTasks = loadData
tableView.reloadData()
}
}
// code for defining the full path
override func viewDidLoad(){
...
let docsDir = NSSearchPathForDirectoriesInDomains(.documentDirectory, .allDomainsMask, true)
fileWithFullPath = docsDir[0].appending("eveningTasks.txt")
load()
}
// code for save
func save() {
let newData:NSArray = NSArray(array: eveningTasks)
newData.write(toFile: fileWithFullPath, atomically: true)
}
// code for load
func load() {
print("path = \(fileWithFullPath)")
if let loadedData = NSArray(contentsOfFile:fileWithFullPath) as? [String] {
evenTasks = loadedData
tableView.reloadData()
}
}