I'm trying to add two numbers in Swift 5, and I want to add some error checks. I don't want to make it possible for a user to click on the plus button if both of the text fields are not filled in. I tried with the if state below but it did not work.
the whole function:
#IBAction func sum(_ sender: Any) {
let one = input1.text
let oneInt = Int(one!)
let two = input2.text
let twoInt = Int(two!)
let total = oneInt! + twoInt!
label.text = "\(total)"
if(input2.text == nil){
addBtn.isEnabled = false
}
if(input1.text == nil){
addBtn.isEnabled = false
}
}
Try to use guard like this. If your input field does not contain any value that field return blank string and when you try to get integer value from that string it will return nil and your add button will be disable.
#IBAction func sum(_ sender: Any) {
guard let text1 = input1.text, let intValue1 = Int(text1) else {
addBtn.isEnabled = false
return
}
guard let text2 = input2.text, let intValue2 = Int(text2) else {
addBtn.isEnabled = false
return
}
label.text = "\(intValue1 + intValue2)"
}
A nice and simple way is to addTarget to your textFiels. This will enable you to handle the events on the text field. In this scenario we'll use .editingChanged and use a single selector to achieve our goal:
What we'll do : We will listen for when someone types something in the textfield. Whenever a text changed was made, we'll check to see if all the textfields was populated and then if it was we enable the sum button.
A small controller sample :: Make sure to read the comments to understand the code faster
import UIKit
class ViewController: UIViewController {
#IBOutlet var textfield1: UITextField!
#IBOutlet var textfield2: UITextField!
#IBOutlet var sumButton: UIButton!
#IBOutlet weak var label: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
sumButton.isEnabled = false /// Disable the button first thing
[textfield1, textfield2].forEach {
$0.addTarget(self, action: #selector(editingChanged(_:)), for: .editingChanged) /// add targets to handle the events (in your case it listens for the 'editingChanged' event )
}
}
#objc func editingChanged(_ textField: UITextField) {
/// Here we just loop through all our textfields
for each in [textfield1, textfield2] {
if let text = each?.text { /// Just make sure the textfields text is not nil
if text.count < 1 {
// If the textfiels text has no value in, then we keep the button disabled and return
sumButton.isEnabled = false
return
}
} else {
/// Else if the text field's text is nill, then return and keep the button disabled
sumButton.isEnabled = false
return
}
}
sumButton.isEnabled = true /// If the code reaches this point, it means the textfields passed all out checks and the button can be enabled
}
#IBAction func sum(_ sender: Any) {
let one = textfield1.text!
let two = textfield2.text!
guard let oneInt = Int(one), let twoInt = Int(two) else {
print("Whatever was in that text fields, couldn't be converted to an Int")
label.text = "Be sure to add numbers."
return
}
let total = oneInt + twoInt
label.text = "\(total)"
}
}
textfields are not nil but empty strings. so make your comparison like :
if input1.text == "" {
// do your check here
}
Seems like you want to start with addBtn.isEnabled = false then update it whenever the user enters two valid integers into the text fields, i.e. Int(input1.text ?? "") != nil && Int(input2.text ?? "") != nil. You can do this by adding a target to your textfields (input1 and input2) for .editingChanged events. For example, if you're doing this in a UIViewController, you can do this in viewDidLoad:
override func viewDidLoad() {
super.viewDidLoad()
addBtn.isEnabled = false
input1.addTarget(self, action: #selector(textFieldDidEdit(_:)), for: .editingChanged)
input2.addTarget(self, action: #selector(textFieldDidEdit(_:)), for: .editingChanged)
}
Where textFieldDidEdit(_:) action looks like:
#objc func textFieldDidEdit(_ sender: UITextField) {
addBtn.isEnabled = Int(input1.text ?? "") != nil && Int(input2.text ?? "") != nil
}
Finally your sum function becomes:
#IBAction func sum(_ sender: UIButton) {
guard let oneInt = Int(input1.text ?? ""), let twoInt = Int(input2.text ?? "") else {
return
}
let total = oneInt + twoInt
label.text = "\(total)"
}
As all of the number validation has moved to the textFieldDidEdit(_:) function.
I'm trying to convert a string into an Int but every time I do it gives me an error.
For example, I have UILabel and it calls resultLabel. Also I have a UITextField.
So what I'm trying to do is first UITextField + second UITextField = resultLabel.
Bottom line, I want from the user to put a number in each UITextField to get the final answer in the resultLabel.
For instance 1 + 1 = 2. But my app gives me 11 or error.
var numberOnScreen:Int = 0
#IBOutlet var first: UITextField!
#IBOutlet var second: UITextField!
#IBOutlet var resultLabel: UILabel!
#IBAction func calculate(_ sender: Any) {
numberOnScreen = Int(first.text!)!
numberOnScreen = Int(second.text!)!
resultLabel.text! = first.text! + second.text!
}
You are doing string concatenation.
First make sure your textfield text are not nil & convert string to int and it can be nil. So you have use if let to make sure the converted values are not nil
if let firstText = firstTextfield.text, let secondText = secondTextfield.text, let firstValue = Int(firstText), let secondValue = Int(secondText) {
let plusValue = firstValue + secondValue
}
First of all if you use + with String, it mean you are concatenating two strings.
So "1" + "1" = "11"
Try it to resolve your problem:
#IBAction func calculate(_ sender: Any) {
guard let first = first.text, let second = second.text, let firstNum = Int(first), let secondNum = Int(second) else {
return
}
let result = firstNum + secondNum
resultLabel.text = String(result)
}
class ViewController: UIViewController {
#IBOutlet weak var label: UILabel!
var userIsInTheMiddleOfTypingNumber: Bool = false
#IBAction func appendDigit(sender: UIButton) {
let digit = sender.currentTitle!
if (userIsInTheMiddleOfTypingNumber) {
label.text = label.text! + digit
}
else {
label.text = digit
userIsInTheMiddleOfTypingNumber = true
}
}
}
I am currently creating a calculator app. For some reason, when I run the simulator and try to input some digits in, the siumulator freezes, and the error of bad_instruction appears on the line:
label.text = digit
How would I fix this situation?
Looks like you forgot to connect the label in the Storyboard with the outlet.
Looks like the currentTitle property is nil which results in a crash. You are force unwrapping the property without any nil check.
#IBAction func appendDigit(sender: UIButton) {
if let digit = sender.currentTitle {
if (userIsInTheMiddleOfTypingNumber) {
label.text = label.text! + digit
}
else {
label.text = digit
userIsInTheMiddleOfTypingNumber = true
}
}
}
OR
It could be the reason specified by #dasdom
I'm following the Stanford Videos for iOS development and I am using Xcode 7 with Swift 2.
I wrote the code from the video line by line, however I keep getting an error.
import UIKit
class ViewController: UIViewController
{
#IBOutlet weak var display: UILabel!
var userIsTyping = false
#IBAction func AppendDigit(sender: UIButton) {
let digit = sender.currentTitle!
if userIsTyping {
display.text = display.text! + digit
} else {
display.text = digit
userIsTyping = true
}
}
var operandStack = Array<Double>()
#IBAction func enter() {
userIsTyping = false
operandStack.append(displayValue)
}
var displayValue: Double {
get{
return NSNumberFormatter().numberFromString(display.text!)!.doubleValue
}
set (newValue){
display.text = "\(newValue)"
userIsTyping = false
}
}
}
At the line where I return
NumberFormatter().numberFromString(display.text!)!.doubleValue
I get an error of
Thread 1: EXC_BAD_INSTRUCTION(code=EXC_1386_INVOP,subcode=0x0)
A conversion can fail. The result can be nil. The "!" means "compiler, I am 100 percent sure that the result can never be nil, so if it is ever nil then please crash". Guess what, sometimes it is nil.
Use "if let".
PS. I think it is very, very unhealthy to take user interface elements (like the title of a button) and to assume they have certain values.
You are much better off substituting that return statement with a much simpler:
return Double(display.text!)!
let Number = (NSNumberFormatter().numberFromString(xtxt.text!)as! Double)
return Number
The application basically calculates acceleration by inputting Initial and final velocity and time and then use a formula to calculate acceleration. However, since the values in the text boxes are string, I am unable to convert them to integers.
#IBOutlet var txtBox1 : UITextField
#IBOutlet var txtBox2 : UITextField
#IBOutlet var txtBox3 : UITextField
#IBOutlet var lblAnswer : UILabel
#IBAction func btn1(sender : AnyObject) {
let answer1 = "The acceleration is"
var answer2 = txtBox1
var answer3 = txtBox2
var answer4 = txtBox3
Updated answer for Swift 2.0+:
toInt() method gives an error, as it was removed from String in Swift 2.x. Instead, the Int type now has an initializer that accepts a String:
let a: Int? = Int(firstTextField.text)
let b: Int? = Int(secondTextField.text)
Basic Idea, note that this only works in Swift 1.x (check out ParaSara's answer to see how it works in Swift 2.x):
// toInt returns optional that's why we used a:Int?
let a:Int? = firstText.text.toInt() // firstText is UITextField
let b:Int? = secondText.text.toInt() // secondText is UITextField
// check a and b before unwrapping using !
if a && b {
var ans = a! + b!
answerLabel.text = "Answer is \(ans)" // answerLabel ie UILabel
} else {
answerLabel.text = "Input values are not numeric"
}
Update for Swift 4
...
let a:Int? = Int(firstText.text) // firstText is UITextField
let b:Int? = Int(secondText.text) // secondText is UITextField
...
myString.toInt() - convert the string value into int .
Swift 3.x
If you have an integer hiding inside a string, you can convertby using the integer's constructor, like this:
let myInt = Int(textField.text)
As with other data types (Float and Double) you can also convert by using NSString:
let myString = "556"
let myInt = (myString as NSString).integerValue
You can use NSNumberFormatter().numberFromString(yourNumberString). It's great because it returns an an optional that you can then test with if let to determine if the conversion was successful.
eg.
var myString = "\(10)"
if let myNumber = NSNumberFormatter().numberFromString(myString) {
var myInt = myNumber.integerValue
// do what you need to do with myInt
} else {
// what ever error code you need to write
}
Swift 5
var myString = "\(10)"
if let myNumber = NumberFormatter().number(from: myString) {
var myInt = myNumber.intValue
// do what you need to do with myInt
} else {
// what ever error code you need to write
}
edit/update: Xcode 11.4 • Swift 5.2
Please check the comments through the code
IntegerField.swift file contents:
import UIKit
class IntegerField: UITextField {
// returns the textfield contents, removes non digit characters and converts the result to an integer value
var value: Int { string.digits.integer ?? 0 }
var maxValue: Int = 999_999_999
private var lastValue: Int = 0
override func willMove(toSuperview newSuperview: UIView?) {
// adds a target to the textfield to monitor when the text changes
addTarget(self, action: #selector(editingChanged), for: .editingChanged)
// sets the keyboard type to digits only
keyboardType = .numberPad
// set the text alignment to right
textAlignment = .right
// sends an editingChanged action to force the textfield to be updated
sendActions(for: .editingChanged)
}
// deletes the last digit of the text field
override func deleteBackward() {
// note that the field text property default value is an empty string so force unwrap its value is safe
// note also that collection remove at requires a non empty collection which is true as well in this case so no need to check if the collection is not empty.
text!.remove(at: text!.index(before: text!.endIndex))
// sends an editingChanged action to force the textfield to be updated
sendActions(for: .editingChanged)
}
#objc func editingChanged() {
guard value <= maxValue else {
text = Formatter.decimal.string(for: lastValue)
return
}
// This will format the textfield respecting the user device locale and settings
text = Formatter.decimal.string(for: value)
print("Value:", value)
lastValue = value
}
}
You would need to add those extensions to your project as well:
Extensions UITextField.swift file contents:
import UIKit
extension UITextField {
var string: String { text ?? "" }
}
Extensions Formatter.swift file contents:
import Foundation
extension Formatter {
static let decimal = NumberFormatter(numberStyle: .decimal)
}
Extensions NumberFormatter.swift file contents:
import Foundation
extension NumberFormatter {
convenience init(numberStyle: Style) {
self.init()
self.numberStyle = numberStyle
}
}
Extensions StringProtocol.swift file contents:
extension StringProtocol where Self: RangeReplaceableCollection {
var digits: Self { filter(\.isWholeNumber) }
var integer: Int? { Int(self) }
}
Sample project
swift 4.0
let stringNumber = "123"
let number = Int(stringNumber) //here number is of type "Int?"
//using Forced Unwrapping
if number != nil {
//string is converted to Int
}
you could also use Optional Binding other than forced binding.
eg:
if let number = Int(stringNumber) {
// number is of type Int
}
In Swift 4.2 and Xcode 10.1
let string = "789"
if let intValue = Int(string) {
print(intValue)
}
let integerValue = 789
let stringValue = String(integerValue)
OR
let stringValue = "\(integerValue)"
print(stringValue)
//Xcode 8.1 and swift 3.0
We can also handle it by Optional Binding, Simply
let occur = "10"
if let occ = Int(occur) {
print("By optional binding :", occ*2) // 20
}
Swift 3
The simplest and more secure way is:
#IBOutlet var textFieldA : UITextField
#IBOutlet var textFieldB : UITextField
#IBOutlet var answerLabel : UILabel
#IBAction func calculate(sender : AnyObject) {
if let intValueA = Int(textFieldA),
let intValueB = Int(textFieldB) {
let result = intValueA + intValueB
answerLabel.text = "The acceleration is \(result)"
}
else {
answerLabel.text = "The value \(intValueA) and/or \(intValueB) are not a valid integer value"
}
}
Avoid invalid values setting keyboard type to number pad:
textFieldA.keyboardType = .numberPad
textFieldB.keyboardType = .numberPad
In Swift 4:
extension String {
var numberValue:NSNumber? {
let formatter = NumberFormatter()
formatter.numberStyle = .decimal
return formatter.number(from: self)
}
}
let someFloat = "12".numberValue
Useful for String to Int and other type
extension String {
//Converts String to Int
public func toInt() -> Int? {
if let num = NumberFormatter().number(from: self) {
return num.intValue
} else {
return nil
}
}
//Converts String to Double
public func toDouble() -> Double? {
if let num = NumberFormatter().number(from: self) {
return num.doubleValue
} else {
return nil
}
}
/// EZSE: Converts String to Float
public func toFloat() -> Float? {
if let num = NumberFormatter().number(from: self) {
return num.floatValue
} else {
return nil
}
}
//Converts String to Bool
public func toBool() -> Bool? {
return (self as NSString).boolValue
}
}
Use it like :
"123".toInt() // 123
i have made a simple program, where you have 2 txt field you take input form the user and add them to make it simpler to understand please find the code below.
#IBOutlet weak var result: UILabel!
#IBOutlet weak var one: UITextField!
#IBOutlet weak var two: UITextField!
#IBAction func add(sender: AnyObject) {
let count = Int(one.text!)
let cal = Int(two.text!)
let sum = count! + cal!
result.text = "Sum is \(sum)"
}
hope this helps.
Swift 3.0
Try this, you don't need to check for any condition I have done everything just use this function. Send anything string, number, float, double ,etc,. you get a number as a value or 0 if it is unable to convert your value
Function:
func getNumber(number: Any?) -> NSNumber {
guard let statusNumber:NSNumber = number as? NSNumber else
{
guard let statString:String = number as? String else
{
return 0
}
if let myInteger = Int(statString)
{
return NSNumber(value:myInteger)
}
else{
return 0
}
}
return statusNumber
}
Usage:
Add the above function in code and to convert use
let myNumber = getNumber(number: myString)
if the myString has a number or string it returns the number else it returns 0
Example 1:
let number:String = "9834"
print("printing number \(getNumber(number: number))")
Output: printing number 9834
Example 2:
let number:Double = 9834
print("printing number \(getNumber(number: number))")
Output: printing number 9834
Example 3:
let number = 9834
print("printing number \(getNumber(number: number))")
Output: printing number 9834
About int() and Swift 2.x: if you get a nil value after conversion check if you try to convert a string with a big number (for example: 1073741824), in this case try:
let bytesInternet : Int64 = Int64(bytesInternetString)!
Latest swift3 this code is simply to convert string to int
let myString = "556"
let myInt = Int(myString)
Because a string might contain non-numerical characters you should use a guard to protect the operation. Example:
guard let labelInt:Int = Int(labelString) else {
return
}
useLabelInt()
I recently got the same issue. Below solution is work for me:
let strValue = "123"
let result = (strValue as NSString).integerValue
Swift5 float or int string to int:
extension String {
func convertStringToInt() -> Int {
return Int(Double(self) ?? 0.0)
}
}
let doubleStr = "4.2"
// print 4
print(doubleStr.convertStringToInt())
let intStr = "4"
// print 4
print(intStr.convertStringToInt())
Use this:
// get the values from text boxes
let a:Double = firstText.text.bridgeToObjectiveC().doubleValue
let b:Double = secondText.text.bridgeToObjectiveC().doubleValue
// we checking against 0.0, because above function return 0.0 if it gets failed to convert
if (a != 0.0) && (b != 0.0) {
var ans = a + b
answerLabel.text = "Answer is \(ans)"
} else {
answerLabel.text = "Input values are not numberic"
}
OR
Make your UITextField KeyboardType as DecimalTab from your XIB or storyboard, and remove any if condition for doing any calculation, ie.
var ans = a + b
answerLabel.text = "Answer is \(ans)"
Because keyboard type is DecimalPad there is no chance to enter other 0-9 or .
Hope this help !!
// To convert user input (i.e string) to int for calculation.I did this , and it works.
let num:Int? = Int(firstTextField.text!);
let sum:Int = num!-2
print(sum);
This works for me
var a:Int? = Int(userInput.text!)
for Swift3.x
extension String {
func toInt(defaultValue: Int) -> Int {
if let n = Int(self.trimmingCharacters(in: CharacterSet.whitespacesAndNewlines)) {
return n
} else {
return defaultValue
}
}
}
Swift 4, Swift 5
There are different cases to convert from something to something data type, it depends the input.
If the input data type is Any, we have to use as before convert to actual data type, then convert to data type what we want. For example:
func justGetDummyString() -> Any {
return "2000"
}
let dummyString: String = (justGetDummyString() as? String) ?? "" // output = "2000"
let dummyInt: Int = Int(dummyString) ?? 0 // output = 2000
for Alternative solution. You can use extension a native type. You can test with playground.
extension String {
func add(a: Int) -> Int? {
if let b = Int(self) {
return b + a
}
else {
return nil
}
}
}
"2".add(1)
My solution is to have a general extension for string to int conversion.
extension String {
// default: it is a number suitable for your project if the string is not an integer
func toInt(default: Int) -> Int {
if let result = Int(self) {
return result
}
else {
return default
}
}
}
#IBAction func calculateAclr(_ sender: Any) {
if let addition = addition(arrayString: [txtBox1.text, txtBox2.text, txtBox3.text]) {
print("Answer = \(addition)")
lblAnswer.text = "\(addition)"
}
}
func addition(arrayString: [Any?]) -> Int? {
var answer:Int?
for arrayElement in arrayString {
if let stringValue = arrayElement, let intValue = Int(stringValue) {
answer = (answer ?? 0) + intValue
}
}
return answer
}
Question : string "4.0000" can not be convert into integer using Int("4.000")?
Answer : Int() check string is integer or not if yes then give you integer and otherwise nil. but Float or Double can convert any number string to respective Float or Double without giving nil. Example if you have "45" integer string but using Float("45") gives you 45.0 float value or using Double("4567") gives you 45.0.
Solution : NSString(string: "45.000").integerValue or Int(Float("45.000")!)! to get correct result.
An Int in Swift contains an initializer that accepts a String. It returns an optional Int? as the conversion can fail if the string contains not a number.
By using an if let statement you can validate whether the conversion succeeded.
So your code become something like this:
#IBOutlet var txtBox1 : UITextField
#IBOutlet var txtBox2 : UITextField
#IBOutlet var txtBox3 : UITextField
#IBOutlet var lblAnswer : UILabel
#IBAction func btn1(sender : AnyObject) {
let answer1 = "The acceleration is"
var answer2 = txtBox1
var answer3 = txtBox2
var answer4 = txtBox3
if let intAnswer = Int(txtBox1.text) {
// Correctly converted
}
}
Swift 5.0 and Above
Working
In case if you are splitting the String it creates two substrings and not two Strings . This below method will check for Any and convert it t0 NSNumber its easy to convert a NSNumber to Int, Float what ever data type you need.
Actual Code
//Convert Any To Number Object Removing Optional Key Word.
public func getNumber(number: Any) -> NSNumber{
guard let statusNumber:NSNumber = number as? NSNumber else {
guard let statString:String = number as? String else {
guard let statSubStr : Substring = number as? Substring else {
return 0
}
if let myInteger = Int(statSubStr) {
return NSNumber(value:myInteger)
}
else{
return 0
}
}
if let myInteger = Int(statString) {
return NSNumber(value:myInteger)
}
else if let myFloat = Float(statString) {
return NSNumber(value:myFloat)
}else {
return 0
}
}
return statusNumber }
Usage
if let hourVal = getNumber(number: hourStr) as? Int {
}
Passing String to check and convert to Double
Double(getNumber(number: dict["OUT"] ?? 0)
As of swift 3, I have to force my #%#! string & int with a "!" otherwise it just doesn't work.
For example:
let prefs = UserDefaults.standard
var counter: String!
counter = prefs.string(forKey:"counter")
print("counter: \(counter!)")
var counterInt = Int(counter!)
counterInt = counterInt! + 1
print("counterInt: \(counterInt!)")
OUTPUT:
counter: 1
counterInt: 2