app development Archives

SWIFT cheat sheet

I’ve added some swift codes which can be helpful for beginners. You can bookmark this page, as it can be used for quick recall.

Declare variables in swift:

 // String
var name = "Bein"  // witout data type
var longName:String = "Andrew Bein" // with data type
        
// Integer
var age = 35
var longAge: Int = 35
        
// Float
var share = 82.3
var longShare: Float = 82.3
        
// Double
var pi = 3.1415926536
var longPi:Double = 3.1415926536

// String

var name = "Bein" // witout data type

var longName:String = "Andrew Bein" // with data type

// Integer

var age = 35

var longAge: Int = 35

// Float

var share = 82.3

var longShare: Float = 82.3

// Double

var pi = 3.1415926536

var longPi:Double = 3.1415926536

Concatenate strings in swift

var firstName = "Andrew"
var lastName = "Bein"
var fullName = firstName + lastName

var firstName = "Andrew"

var lastName = "Bein"

var fullName = firstName + lastName

Declare arrays in swift

var fruits = ["mango", "strawberry", "apple", "banana", "cherry", "grape"]

1	var fruits = ["mango", "strawberry", "apple", "banana", "cherry", "grape"]

Find number of elements in array in swift

fruits.count
// Example
println(fruits.count)

fruits.count

// Example

println(fruits.count)

Tuples in swift

var paymentMethod = ("Credit Card", "Cash on delivery", "Cheque");

1	var paymentMethod = ("Credit Card", "Cash on delivery", "Cheque");

Declare Class in swift

class ClassName {
    // define variables and methods
    var name = "Bein"
    var age = 35
}

class ClassName {

// define variables and methods

var name = "Bein"

var age = 35

}

Instantiate class in swift

var myClass = ClassName();

// Set properties of class
myClass.name = "Dan Reynolds"
myClass.age = 30

var myClass = ClassName();

// Set properties of class

myClass.name = "Dan Reynolds"

myClass.age = 30

Declare Struct (or structure) in swift

struct StructName {
    // Write codes for struct here
}

struct StructName {

// Write codes for struct here

}

Inherit Class in swift

class ChildClass: ParentClass {
    // add your variables and methods / functions here
}

class ChildClass: ParentClass {

// add your variables and methods / functions here

}

Declare simple method / function without argument and return type:

func functionName () {
        println("Hello World")
}

func functionName () {

println("Hello World")

}

Declare method / function with argument and return type

func fullName(firstName:String, lastName:String) -> String {
        return firstName + lastName;
}

func fullName(firstName:String, lastName:String) -> String {

return firstName + lastName;

}

For loop

var i: Int
for i = 0; i < 7; i++ {
    println("Line:  \(i)")
}

var i: Int

for i = 0; i < 7; i++ {

println("Line: \(i)")

}

For loop in another form

for i in 0..<7 {
    println("Number: \(i)");        
}

for i in 0..<7 {

println("Number: \(i)");

}

For loop in array

let paymentMethods = ["Credit Card", "Cash on delivery", "Check", "Others"]
for method in paymentMethods {
    println("Hello, \(method)!")
}

let paymentMethods = ["Credit Card", "Cash on delivery", "Check", "Others"]

for method in paymentMethods {

println("Hello, \(method)!")

}

While loop:

var a = 5;
while a < 100 {
    a = a + a
}

var a = 5;

while a < 100 {

a = a + a

}

How to add UIImageView programmatically in swift

You can add UIImageView programmatically in your iOS application at run time. You can get the image file from server. To avoid complexity, we will use local image file. First create a new project. Copy and paste any image from your local computer in the project. You can download image from here.

UPDATE: After downloading the image, copy it to your project folder. Best way to do this is open the Project navigator of Xcode (If it is not already opened). Then open the folder where your image is located. Drag and drop the image from Finder to you Project Navigator. When a dialog box appear, Check “Copy items if needed” to project option.

Before I proceed, let me explain the difference between UIImage and UIImageView.

UIImage: It’s the image that we want to display.

UIImageView: It’s something like frame of the image or placeholder of the image where we’ll set our UIImage or image.

Now open your ViewController.swift file.

There are 2 things to add image to your application programmatically.

1. Add image to your “image view”.

2. Add “image view” in your view.

In viewDidLoad method write the following code to add image to your image view:

var image: UIImage = UIImage(named: "camomile")! // Name of the image that we copied. You don't have to write extension of the image. 

var imageView = UIImageView(image: image)

var image: UIImage = UIImage(named: "camomile")! // Name of the image that we copied. You don't have to write extension of the image.

var imageView = UIImageView(image: image)

Now, let’s add the image view in our main view:

self.view.addSubview(imageView)

1	self.view.addSubview(imageView)

We can also set width and height of the image:

imageView.frame = CGRectMake(0,0,100,200)

1	imageView.frame = CGRectMake(0,0,100,200)

The whole code is:

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        
        var image: UIImage = UIImage(named: "camomile")!
        
        var imageView = UIImageView(image: image)
        self.view.addSubview(imageView)
        
        imageView.frame = CGRectMake(0,0,100,200)
        
        
        
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


}

import UIKit

class ViewController: UIViewController {

override func viewDidLoad() {

super.viewDidLoad()

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

var image: UIImage = UIImage(named: "camomile")!

var imageView = UIImageView(image: image)

self.view.addSubview(imageView)

imageView.frame = CGRectMake(0,0,100,200)

}

override func didReceiveMemoryWarning() {

super.didReceiveMemoryWarning()

// Dispose of any resources that can be recreated.

}

How to add UITextField, UITextView and UILabel programmatically in swift

In iOS app development, sometime we need to add Textfields, textviews, labels etc programmatically. It gives you control over customizing styles, size and position of them. I’m going to place codes (swift Language) here so that you can get all of them from one place.

UITextField:

func textField() {
        let textField = UITextField(frame: CGRectMake(20.0, 30.0, 100.0, 30.0))
        textField.textAlignment = NSTextAlignment.Center
        textField.textColor = UIColor.blueColor()
        textField.borderStyle = UITextBorderStyle.Line
        textField.autocapitalizationType = UITextAutocapitalizationType.Words // If you need any capitalization
        self.view.addSubview(textField)
    }

func textField() {

let textField = UITextField(frame: CGRectMake(20.0, 30.0, 100.0, 30.0))

textField.textAlignment = NSTextAlignment.Center

textField.textColor = UIColor.blueColor()

textField.borderStyle = UITextBorderStyle.Line

textField.autocapitalizationType = UITextAutocapitalizationType.Words // If you need any capitalization

self.view.addSubview(textField)

}

TextView:

func textView() {
        let textView = UITextView(frame: CGRectMake(20.0, 30.0, 300.0, 30.0))
        textView.textAlignment = NSTextAlignment.Center
        textView.textColor = UIColor.blueColor()
        textView.backgroundColor = UIColor.redColor()
        self.view.addSubview(textView)
    }

func textView() {

let textView = UITextView(frame: CGRectMake(20.0, 30.0, 300.0, 30.0))

textView.textAlignment = NSTextAlignment.Center

textView.textColor = UIColor.blueColor()

textView.backgroundColor = UIColor.redColor()

self.view.addSubview(textView)

}

Label:

    func textView() {
        let textView = UITextView(frame: CGRectMake(20.0, 30.0, 300.0, 30.0))
        textView.textAlignment = NSTextAlignment.Center
        textView.textColor = UIColor.blueColor()
        textView.backgroundColor = UIColor.redColor()
        self.view.addSubview(textView)
    }

func textView() {

let textView = UITextView(frame: CGRectMake(20.0, 30.0, 300.0, 30.0))

textView.textAlignment = NSTextAlignment.Center

textView.textColor = UIColor.blueColor()

textView.backgroundColor = UIColor.redColor()

self.view.addSubview(textView)

}

How to add UIButton programmatically in SWIFT

In iOS app development sometime we’ve to create Buttons programmatically or dynamically. Today, I’ll show you how to do this using SWIFT programming language.

Let’s create a new Single View iOS application in Xcode. Name theÂ project “DynamicButton”. SelectÂ swift as programming language.

Now go to ViewController.swift. In ViewDidLoad method we’ll write some codes that will add one button to the screen automatically at run time.

Let’s create a new method createButton and write some codes inside the method that will do the magic:

func createButton () {
        let button = UIButton();
        button.setTitle("Add", forState: .Normal)
        button.setTitleColor(UIColor.blueColor(), forState: .Normal)
        button.frame = CGRectMake(15, -50, 200, 100)
        self.view.addSubview(button)
    }

func createButton () {

let button = UIButton();

button.setTitle("Add", forState: .Normal)

button.setTitleColor(UIColor.blueColor(), forState: .Normal)

button.frame = CGRectMake(15, -50, 200, 100)

self.view.addSubview(button)

}

Explanation:

First we initialize a button object and keep it in button variable.

let button = UIButton();

1	let button = UIButton();

Then we set title and color of title of it.

button.setTitle("Add", forState: .Normal)
button.setTitleColor(UIColor.blueColor(), forState: .Normal)

1 2	button.setTitle("Add", forState: .Normal) button.setTitleColor(UIColor.blueColor(), forState: .Normal)

In the following line of code, we add position and size of the button.

button.frame = CGRectMake(15, 50, 200, 100) // X, Y, width, height

1	button.frame = CGRectMake(15, 50, 200, 100) // X, Y, width, height

Add the button to view.

self.view.addSubview(button)

1	self.view.addSubview(button)

Finally let’s call the createButton in viewDidLoad method.

override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        createButton()
    }

override func viewDidLoad() {

super.viewDidLoad()

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

createButton()

}

Now if you run the project (cmd + R) you can see a button created. If you tap on the button, nothing will happen at this moment. To call a method when button is pressed, we can write:

button.addTarget(self, action: "buttonPressed:", forControlEvents: .TouchUpInside)

1	button.addTarget(self, action: "buttonPressed:", forControlEvents: .TouchUpInside)

Do not forget to add ‘:’ after action method name (i.e. buttonPressed:). In action parameter of .addTarget, you set the method name that should be called. Now write buttonPressed method.

    func buttonPressed(sender: UIButton!) {
        var alertView = UIAlertView();
        alertView.addButtonWithTitle("OK");
        alertView.title = "Alert";
        alertView.message = "Button Pressed!!!";
        alertView.show();
    }

func buttonPressed(sender: UIButton!) {

var alertView = UIAlertView();

alertView.addButtonWithTitle("OK");

alertView.title = "Alert";

alertView.message = "Button Pressed!!!";

alertView.show();

}

The buttonPressed: method simply displays an alert view. Now run the project and view result.

The whole ViewController.swift will look like this:

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        createButton()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        
        
        
    }
    
    
    func createButton () {
        let button = UIButton();
        button.setTitle("Add", forState: .Normal)
        button.setTitleColor(UIColor.blueColor(), forState: .Normal)
        button.frame = CGRectMake(200, 65, 46, 30) // X, Y, width, height
        button.addTarget(self, action: "buttonPressed:", forControlEvents: .TouchUpInside)
        self.view.addSubview(button)
    }
    
    
    
    func buttonPressed(sender: UIButton!) {
        var alertView = UIAlertView();
        alertView.addButtonWithTitle("Done");
        alertView.title = "Alert!";
        alertView.message = "Button Pressed!!!";
        alertView.show();
    }


}

import UIKit

class ViewController: UIViewController {

override func viewDidLoad() {

super.viewDidLoad()

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

createButton()

}

override func didReceiveMemoryWarning() {

super.didReceiveMemoryWarning()

}

func createButton () {

let button = UIButton();

button.setTitle("Add", forState: .Normal)

button.setTitleColor(UIColor.blueColor(), forState: .Normal)

button.frame = CGRectMake(200, 65, 46, 30) // X, Y, width, height

button.addTarget(self, action: "buttonPressed:", forControlEvents: .TouchUpInside)

self.view.addSubview(button)

}

func buttonPressed(sender: UIButton!) {

var alertView = UIAlertView();

alertView.addButtonWithTitle("Done");

alertView.title = "Alert!";

alertView.message = "Button Pressed!!!";

alertView.show();

}

Still feeling tired? Click here to download the project.

How to use Core-Data with SWIFT

Core data is a framework that is used to save data in iOS app development and OS X platform. Today we’ll develop an application using SWIFT programming language that will have a textfield, a button and a textview that will save and display data fetched from Core Data. To learn more about Core-Data please visit:

Introduction to Core Data Programming Guide

Summary:

Step 1: Create Project

Step 2: Design Core-Data database

Step 3: Write script to save and fetch data from core data.

Step 1:

1. Create a new project in Xcode. In first window of the wizardÂ select Single view application. In next screen, select SWIFT from dropdown box and also check “Use Core Data” checkbox (bottom of the wizard). Please use “NotePad” as your project name.

2. Open Main.storyboard and add a textfield, a button. Below the buttonÂ add big textview. ( Note: textfield is for one line. For multiple lines use textview).

Step 2:

1. Now, open NotePad.xcdatamodeld (YourProjectName.xcdatamodeld). This is the place where you design your database.

2. Here you add Entity (Entity is similar to Table of Oracle / MySql database, but not exactly). At the bottom of the page, you will see Add Entity button (1). Click on it. New entity (2) will be added. By double clicking on it, you can change it’s name. I changed it to “Note”

3. Now select the entity (if it’s not already selected). Add “Attribute” to it by clicking + button (3) below the Attributes section. Attribute is similar to column of a table. For each attribute we should select a type from dropdown box. I’m using only one attribute “paper” with type “String”.

4. At this point you have to do an important thing. InÂ Utilities panel (Right side bar), you will see a box labeled: “Class” (4) in entity section. Write here : NotePad.Note; Actually, it should be ApplicationName.EntityName

5. Now we’ll generate Entity Classes. To do this, go to Editor > Create NSManagedObjectSubclass. Select theÂ data model (It’s the file name that we have worked on). In next screen, select Entity name. We’ve only one Entity. Click next. Now, you will see a dialog box for saving entity file. Here, from language dropdown box select swift and finally click Create button.

Step 3:

1. Add outlets to textField and textview.

2. Add IBAction to button. You can also rename the button to “Add”

3. Open ViewController.swift.

We’ll edit this file. Before we proceed, let me give you an example. Suppose we have some food, one tray and a refrigerator. To save the food, we’ve to put it on the tray and keep the tray inside refrigerator. Saving method of Core data is similar. Here data is food, managedObject is tray and managedObject.save is equivalent to keeping tray contained food inside refrigerator.

First import CoreData in your viewController

import CoreData

1	import CoreData

declare an array NSManagedObject below IBOutlet declaration. so the code will look like this:

import UIKit
import CoreData

class ViewController: UIViewController {
    
    //-- Declare Outlets --//
    @IBOutlet weak var textFieldNote: UITextField!
    
    @IBOutlet weak var textViewAllNotes: UITextView!
    
    //-- declare allPapers variables 
    // it will contain all data fetched from core data --//
    
    var allPapers = [NSManagedObject]()

}

import UIKit

import CoreData

class ViewController: UIViewController {

//-- Declare Outlets --//

@IBOutlet weak var textFieldNote: UITextField!

@IBOutlet weak var textViewAllNotes: UITextView!

//-- declare allPapers variables

// it will contain all data fetched from core data --//

var allPapers = [NSManagedObject]()

}

To fetch data from CoreData we can use following method:

//-- fetch data from CoreData --//
    func fetchPapers () {
        
        //-- CoreData starts --//
        let appDelegate = UIApplication.sharedApplication().delegate as AppDelegate
        var managedObjectContext = appDelegate.managedObjectContext!
        
        let fetchRequest = NSFetchRequest(entityName: "Note")
        
        var error: NSError?
        
        let fetchResults = managedObjectContext.executeFetchRequest(fetchRequest, error: &error) as [NSManagedObject]?
        
        if let results = fetchResults {
            allPapers = results
        } else {
            println("Not fetched\(error), \(error!.userInfo)")
        }
        
        //-- CoreData ends --//
        
        var textToDisplay = ""
        
        for paper in allPapers {
            textToDisplay += paper.valueForKey("paper") as String
            textToDisplay += "\n"
            
        }
        
        textViewAllNotes.text = textToDisplay

    }

//-- fetch data from CoreData --//

func fetchPapers () {

//-- CoreData starts --//

let appDelegate = UIApplication.sharedApplication().delegate as AppDelegate

var managedObjectContext = appDelegate.managedObjectContext!

let fetchRequest = NSFetchRequest(entityName: "Note")

var error: NSError?

let fetchResults = managedObjectContext.executeFetchRequest(fetchRequest, error: &error) as [NSManagedObject]?

if let results = fetchResults {

allPapers = results

} else {

println("Not fetched\(error), \(error!.userInfo)")

}

//-- CoreData ends --//

var textToDisplay = ""

for paper in allPapers {

textToDisplay += paper.valueForKey("paper") as String

textToDisplay += "\n"

}

textViewAllNotes.text = textToDisplay

}

Above method fetches all data in Note entity. At the end of the method, we used for loop to get each text inside paper and add them in a local variable. finally show all texts in large text view.

To save data in Core data use following code. We are saving text in paper attribute (column) of Note entity (table)

//-- Save to CoreData --//
    func saveNote(myText:String){
        
        //-- Get a tray first --//
        let appDelegate = UIApplication.sharedApplication().delegate as AppDelegate
        let managedObjectContext = appDelegate.managedObjectContext!
        
        
        let entity = NSEntityDescription.entityForName("Note", inManagedObjectContext: managedObjectContext)
        
        let paper = NSManagedObject(entity: entity!, insertIntoManagedObjectContext: managedObjectContext)
        
        
        //-- put food on tray --//
        paper.setValue(myText, forKey: "paper")
        
        allPapers.append(paper)
        
        var error: NSError?
        
        //-- put the tray inside refrigerator --//
        
        if managedObjectContext.save(&error) {
            println("Couldn't save\(error?.userInfo)")
        }
        
        
        fetchPapers()
        
        
    }

//-- Save to CoreData --//

func saveNote(myText:String){

//-- Get a tray first --//

let appDelegate = UIApplication.sharedApplication().delegate as AppDelegate

let managedObjectContext = appDelegate.managedObjectContext!

let entity = NSEntityDescription.entityForName("Note", inManagedObjectContext: managedObjectContext)

let paper = NSManagedObject(entity: entity!, insertIntoManagedObjectContext: managedObjectContext)

//-- put food on tray --//

paper.setValue(myText, forKey: "paper")

allPapers.append(paper)

var error: NSError?

//-- put the tray inside refrigerator --//

if managedObjectContext.save(&error) {

println("Couldn't save\(error?.userInfo)")

}

fetchPapers()

}

Now implement saveNote in IBAction actionAddNote. Clear the text field so that you can add new note.

    @IBAction func actionAddNote(sender: AnyObject) {
        var myText = textFieldNote?.text
        saveNote(myText!)
        textFieldNote.text = ""
        
    }

@IBAction func actionAddNote(sender: AnyObject) {

var myText = textFieldNote?.text

saveNote(myText!)

textFieldNote.text = ""

}

Full source code of ViewController.swift. You can also download the whole project from the link provided at the end this tutorial.

import UIKit
//-- Import CoreData --//
import CoreData


class ViewController: UIViewController {
    
    //-- Declare Outlets --//
    @IBOutlet weak var textFieldNote: UITextField!
    
    @IBOutlet weak var textViewAllNotes: UITextView!
    
    //-- declare allPapers variables 
    // it will contain all data fetched from core data --//
    
    var allPapers = [NSManagedObject]()

    override func viewDidLoad() {
        super.viewDidLoad()
    }
    
    
    override func viewWillAppear(animated: Bool) {
        
        fetchPapers()
        
    }
    
    
    //-- fetch data from CoreData --//
    func fetchPapers () {
        
        //-- CoreData starts --//
        let appDelegate = UIApplication.sharedApplication().delegate as AppDelegate
        var managedObjectContext = appDelegate.managedObjectContext!
        
        let fetchRequest = NSFetchRequest(entityName: "Note")
        
        var error: NSError?
        
        let fetchResults = managedObjectContext.executeFetchRequest(fetchRequest, error: &error) as [NSManagedObject]?
        
        if let results = fetchResults {
            allPapers = results
        } else {
            println("Not fetched\(error), \(error!.userInfo)")
        }
        
        //-- CoreData ends --//
        
        var textToDisplay = ""
        
        for paper in allPapers {
            textToDisplay += paper.valueForKey("paper") as String
            textToDisplay += "\n"
            
            
        }
        
        textViewAllNotes.text = textToDisplay

    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
    
    
    @IBAction func actionAddNote(sender: AnyObject) {
        var myText = textFieldNote?.text
        saveNote(myText!)
        textFieldNote.text = ""
        
        
    }
    
    
    
    
    //-- Save to CoreData --//
    func saveNote(myText:String){
        
        //-- Get a tray first --//
        let appDelegate = UIApplication.sharedApplication().delegate as AppDelegate
        let managedObjectContext = appDelegate.managedObjectContext!
        
        
        let entity = NSEntityDescription.entityForName("Note", inManagedObjectContext: managedObjectContext)
        
        let paper = NSManagedObject(entity: entity!, insertIntoManagedObjectContext: managedObjectContext)
        
        
        //-- put food on tray --//
        paper.setValue(myText, forKey: "paper")
        
        allPapers.append(paper)
        
        var error: NSError?
        
        //-- put the tray inside refrigerator --//
        
        if managedObjectContext.save(&error) {
            println("Couldn't save\(error?.userInfo)")
        }
        
        
        fetchPapers()
        
        
    }


}

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import UIKit

//-- Import CoreData --//

import CoreData

class ViewController: UIViewController {

//-- Declare Outlets --//

@IBOutlet weak var textFieldNote: UITextField!

@IBOutlet weak var textViewAllNotes: UITextView!

//-- declare allPapers variables

// it will contain all data fetched from core data --//

var allPapers = [NSManagedObject]()

override func viewDidLoad() {

super.viewDidLoad()

}

override func viewWillAppear(animated: Bool) {

fetchPapers()

}

//-- fetch data from CoreData --//

func fetchPapers () {

//-- CoreData starts --//

let appDelegate = UIApplication.sharedApplication().delegate as AppDelegate

var managedObjectContext = appDelegate.managedObjectContext!

let fetchRequest = NSFetchRequest(entityName: "Note")

var error: NSError?

let fetchResults = managedObjectContext.executeFetchRequest(fetchRequest, error: &error) as [NSManagedObject]?

if let results = fetchResults {

allPapers = results

} else {

println("Not fetched\(error), \(error!.userInfo)")

}

//-- CoreData ends --//

var textToDisplay = ""

for paper in allPapers {

textToDisplay += paper.valueForKey("paper") as String

textToDisplay += "\n"

}

textViewAllNotes.text = textToDisplay

}

override func didReceiveMemoryWarning() {

super.didReceiveMemoryWarning()

// Dispose of any resources that can be recreated.

}

@IBAction func actionAddNote(sender: AnyObject) {

var myText = textFieldNote?.text

saveNote(myText!)

textFieldNote.text = ""

}

//-- Save to CoreData --//

func saveNote(myText:String){

//-- Get a tray first --//

let appDelegate = UIApplication.sharedApplication().delegate as AppDelegate

let managedObjectContext = appDelegate.managedObjectContext!

let entity = NSEntityDescription.entityForName("Note", inManagedObjectContext: managedObjectContext)

let paper = NSManagedObject(entity: entity!, insertIntoManagedObjectContext: managedObjectContext)

//-- put food on tray --//

paper.setValue(myText, forKey: "paper")

allPapers.append(paper)

var error: NSError?

//-- put the tray inside refrigerator --//

if managedObjectContext.save(&error) {

println("Couldn't save\(error?.userInfo)")

}

fetchPapers()

}

You can download the whole project by clicking here.

Parsing JSON object by SWIFT

Today we’ll see how to work with JSON in swift language. We’ll develop a simple currency converter. It will convert USD to Euro by using web API that returns JSON data. Here is the basic structure that we are going to do:

Letâ€™s begin.
1. Create a new project “CurrencyConverter” and select swift as programming language. Select Single View from next dialog box.

2. Open Main.storyboard and add a textfield, a button and a label. See screenshot for guide. Weâ€™ll keep everything simple.

3. Open both Main.storyboard and ViewController.swfit in Assistant editor.

a. Create an IBOutlet for textField and name it txtAmount

b. create an IBOutlet of the label (result) and name it labelResult.

c. Create an IBAction for the button and give it name: actionConvert.

4. Open ViewController.swift in standard editor.

Weâ€™ll declare 3 functions (or methods) that will do the following things:

a. getData()
It will get data from server.

func getData(urlToRequest: String) -> NSData{
        return NSData(contentsOfURL: NSURL(string: urlToRequest)!)!
    }

func getData(urlToRequest: String) -> NSData{

return NSData(contentsOfURL: NSURL(string: urlToRequest)!)!

}

b. parseJSON()

This function will convert data received from server into JSON object.

func parseJSON(inputData: NSData) {
       
        var parseError: NSError?
        let parsedObject = NSJSONSerialization.JSONObjectWithData(inputData, options: nil, error:&parseError) as NSDictionary
        
        println(parsedObject)
        
        if let result = parsedObject["v"] as? Float {
            println(result)
            displayResult(result)
        }
    }

func parseJSON(inputData: NSData) {

var parseError: NSError?

let parsedObject = NSJSONSerialization.JSONObjectWithData(inputData, options: nil, error:&parseError) as NSDictionary

println(parsedObject)

if let result = parsedObject["v"] as? Float {

println(result)

displayResult(result)

}

c. displayData()
This function will display the JSON data in UILabel. Call this method inside parseJSON method.

    func displayResult(result: Float) {
        labelResult.text = String(format: "%.3f", result)
    }

func displayResult(result: Float) {

labelResult.text = String(format: "%.3f", result)

}

Finally in actionConvert method (or function), call getData and parseJSON.

    @IBAction func actionConvert(sender: AnyObject) {
        var amount = txtAmount.text
        // You can change the url below to get different currency result. This api converts only one unit. You have to multiply as you require.
        var serverData = getData("http://rate-exchange.appspot.com/currency?from=USD&to=EUR&q="+amount);
        parseJSON(serverData)
    }

@IBAction func actionConvert(sender: AnyObject) {

var amount = txtAmount.text

// You can change the url below to get different currency result. This api converts only one unit. You have to multiply as you require.

var serverData = getData("http://rate-exchange.appspot.com/currency?from=USD&to=EUR&q="+amount);

parseJSON(serverData)

}

Run the application to see the result.

IMPORTANT NOTE: If you want to fetch JSON Array instead of JSON Object (One JSON array contains one or more JSON objects), please use the following method:Â

func parseJSONArray(inputData: NSData) {
        
        var error: NSError?
        var jsonDictionary: Array<NSDictionary> = NSJSONSerialization.JSONObjectWithData(inputData, options: NSJSONReadingOptions.MutableContainers, error: &error) as Array<NSDictionary>
        
    
        var result: NSDictionary = jsonDictionary[0] as NSDictionary
        
        var value = result["key"] as? String
        
    }

func parseJSONArray(inputData: NSData) {

var error: NSError?

var jsonDictionary: Array<NSDictionary> = NSJSONSerialization.JSONObjectWithData(inputData, options: NSJSONReadingOptions.MutableContainers, error: &error) as Array<NSDictionary>

var result: NSDictionary = jsonDictionary[0] as NSDictionary

var value = result["key"] as? String

}