I get an error when declaring i
var users = Array<Dictionary<String,Any>>()
users.append(["Name":"user1","Age":20])
var i:Int = Int(users[0]["Age"])
How to get the int value?
var i = users[0]["Age"] as Int
As GoZoner points out, if you don't know that the downcast will succeed, use:
var i = users[0]["Age"] as? Int
The result will be nil if it fails
Swift 4 answer :
if let str = users[0]["Age"] as? String, let i = Int(str) {
// do what you want with i
}
If you are sure the result is an Int then use:
var i = users[0]["Age"] as! Int
but if you are unsure and want a nil value if it is not an Int then use:
var i = users[0]["Age"] as? Int
“Use the optional form of the type cast operator (as?) when you are
not sure if the downcast will succeed. This form of the operator will
always return an optional value, and the value will be nil if the
downcast was not possible. This enables you to check for a successful
downcast.”
Excerpt From: Apple Inc. “The Swift Programming Language.” iBooks.
https://itun.es/us/jEUH0.l
This may have worked previously, but it's not the answer for Swift 3. Just to clarify, I don't have the answer for Swift 3, below is my testing using the above answer, and clearly it doesn't work.
My data comes from an NSDictionary
print("subvalue[multi] = \(subvalue["multi"]!)")
print("as Int = \(subvalue["multi"]! as? Int)")
if let multiString = subvalue["multi"] as? String {
print("as String = \(multiString)")
print("as Int = \(Int(multiString)!)")
}
The output generated is:
subvalue[multi] = 1
as Int = nil
Just to spell it out:
a) The original value is of type Any? and the value is: 1
b) Casting to Int results in nil
c) Casting to String results in nil (the print lines never execute)
EDIT
The answer is to use NSNumber
let num = subvalue["multi"] as? NSNumber
Then we can convert the number to an integer
let myint = num.intValue
if let id = json["productID"] as? String {
self.productID = Int32(id, radix: 10)!
}
This worked for me. json["productID"] is of type Any.
If it can be cast to a string, then convert it to an Integer.
Related
I am trying to read a string and convert it to an int. I have a solution but it seems way too complicated. I guess I am still trying to wrap my head around unwrapping.
I have posted code below along with the compiler errors that I get with each solution.
In this example I try to read a string from UserDefaults and convert to an integer value.
static func GetSelectedSessionNum() -> Int32 {
var sessionNum : Int32 = 0
let defaults = UserDefaults.standard
let optionalString: String? = defaults.string(forKey: "selectedSessionNum")
// this works but it's too complicated
if let string = optionalString, let myInt = Int32(string) {
return myInt
}
return 0
// Error : optional String? must be unwrapped to a value of type 'String'
let t : String = defaults.string(forKey: "selectedSessionNum")
if let s : String = defaults.string(forKey: "selectedSessionNum") {
// error - Int32? must be unwrapped to a value of Int32
return Int32(s)
}
return 0
}
You need to cast to non optional Int32 in order to match your return type.
You can use any optional binding approach, or change your return type to Int32?
If you want an uncomplicated solution save selectedSessionNum as Int
static func getSelectedSessionNum() -> Int32 {
return Int32(UserDefaults.standard.integer(forKey: "selectedSessionNum"))
}
otherwise double optional binding
if let string = UserDefaults.standard.string(forKey: "selectedSessionNum"), let myInt = Int32(string) {
return myInt
}
or the nil coalescing operator
if let string = UserDefaults.standard.string(forKey: "selectedSessionNum") {
return Int32(string) ?? 0
}
is the proper way
If you want to avoid optional bindings, you can use flatMap, when called on Optional's it allows you to convert one optional to another:
return UserDefaults.standard.string(forKey: "selectedSessionNum").flatMap(Int32.init) ?? 0
You'd also need the ?? (nil coalescing operator) to cover the scenarios where either the initializer fails, or the value is not present in user defaults.
I am a beginner in swift and I am having a problem with convering string to UInt32.
let Generator = (ReadableJSON ["People"] [Person]["F1"].string! as NSString).doubleValue
if Generator == 1 {
NameLabel1 = ReadableJSON ["People"] [Person]["A1"].string as String!
NameImeNaObekt = ReadableJSON ["People"] [Person] ["B1"].string as String!
Picture = ReadableJSON ["People"] [Person] ["E1"].string as String!
} else {
let RGen = arc4random_uniform ("\(Generator)") // here is the error
}
Would you advise me how to fix it. The problem is in the last line, which is red and it says Cannot convert value of type String to UInt32.
The main idea is that I am reading the number from a JSON file and I have to populate this number into the arc4random_uniform.
arc4random_uniform(UInt32)
accept an UInt32 value but you are passing an String value to it
this converts your number to string
"\(Generator)"
the last line should be like this
let RGen = arc4random_uniform (UInt32(Generator))
and if you want to 'RGen' is an String you can do it this way
"\(RGen)"
String(RGen)
var RGen= 0
let RGen =int( arc4random_uniform ("\(Generator)") )
or
let RGen =( arc4random_uniform ("(Generator)") ).toInt
Look here
I was working on an application that used a text field and translated it into an integer. Previously my code
textField.text.toInt()
worked. Now Swift declares this as an error and is telling me to do
textField.text!.toInt()
and it says there is no toInt() and to try using Int(). That doesn't work either. What just happened?
In Swift 2.x, the .toInt() function was removed from String. In replacement, Int now has an initializer that accepts a String
Int(myString)
In your case, you could use Int(textField.text!) insted of textField.text!.toInt()
Swift 1.x
let myString: String = "256"
let myInt: Int? = myString.toInt()
Swift 2.x, 3.x
let myString: String = "256"
let myInt: Int? = Int(myString)
Swift 2
let myString: NSString = "123"
let myStringToInt: Int = Int(myString.intValue)
declare your string as an object NSString
and use the intValue getter
Its easy enough to create your own extension method to put this back in:
extension String {
func toInt() -> Int? {
return Int(self)
}
}
I had the same issued in Payment processing apps.
Swift 1.0
let expMonth = UInt(expirationDate[0].toInt()!)
let expYear = UInt(expirationDate[1].toInt()!)
After in Swift 2.0
let expMonth = Int(expirationDate[0])
let expYear = Int(expirationDate[1])
That gave me some errors too!
This code solved my errors
let myString: String = dataEntered.text! // data entered in textField
var myInt: Int? = Int(myString) // conversion of string to Int
myInt = myInt! * 2 // manipulating the integer sum,difference,product, division
finalOutput.text! = "\(myInt)" // changes finalOutput label to myInt
self.event?["start"].string
The output is = Optional("1423269000000")
I want to get 1423269000000 as an Int
How can we achieve this? I have tried many ways such NSString (but it changed the value)
Your value: 1,423,269,000,000 is bigger than max Int32 value: 2,147,483,647. This may cause unexpected casting value. For more information, check this out: Numeric Types.
Try to run this code:
let maxIntegerValue = Int.max
println("Max integer value is: \(maxIntegerValue)")
In iPhone 4S simulator, the console output is:
Max integer value is: 2147483647
And iPhone 6 simulator, the console output is:
Max integer value is: 9223372036854775807
This information may help you.
But normally to convert Int to String:
let mInt : Int = 123
var mString = String(mInt)
And convert String to Int:
let mString : String = "123"
let mInt : Int? = mString.toInt()
if (mInt != null) {
// converted String to Int
}
Here is my safe way to do this using Optional Binding:
var json : [String:String];
json = ["key":"123"];
if var integerJson = json["key"]!.toInt(){
println("Integer conversion successful : \(integerJson)")
}
else{
println("Integer conversion failed")
}
Output:
Integer conversion successful :123
So this way one can be sure if the conversion was successful or not, using Optional Binding
I'm not sure about your question, but say you have a dictionary (Where it was JSON or not) You can do this:
var dict: [String : String]
dict = ["key1" : "123"]
var x : Int
x = dict["key1"].toInt()
println(x)
Just in case someone's still looking for an updated answer, here's the Swift 5+ version:
let jsonDict = ["key": "123"];
// Validation
guard let value = Int(jsonDict["key"]) else {
print("Error! Unexpected value.")
return
}
print("Integer conversion successful: \(value)")
// Prints "Integer conversion successful: 123"
So I am trying to get the Actual Variable Name as String in Swift, but have not found a way to do so... or maybe I am looking at this problem and solution in a bad angle.
So this is basically what I want to do:
var appId: String? = nil
//This is true, since appId is actually the name of the var appId
if( appId.getVarName = "appId"){
appId = "CommandoFurball"
}
Unfortunately I have not been able to find in apple docs anything that is close to this but this:
varobj.self or reflect(var).summary
however, this gives information of what is inside the variable itself or the type of the variable in this case being String and I want the Actual name of the Variable.
This is officially supported in Swift 3 using #keyPath()
https://github.com/apple/swift-evolution/blob/master/proposals/0062-objc-keypaths.md
Example usage would look like:
NSPredicate(format: "%K == %#", #keyPath(Person.firstName), "Wendy")
In Swift 4 we have something even better: \KeyPath notation
https://github.com/apple/swift-evolution/blob/master/proposals/0161-key-paths.md
NSPredicate(format: "%K == %#", \Person.mother.firstName, "Wendy")
// or
let keyPath = \Person.mother.firstName
NSPredicate(format: "%K == %#", keyPath, "Andrew")
The shorthand is a welcome addition, and being able to reference keypaths from a variable is extremely powerful
As per the updated from this answer, it is supported in Swift 3 via #keyPath
NSPredicate(format: "%K == %#", #keyPath(Person.firstName), "Andrew")
This is my solution
class Test {
var name: String = "Ido"
var lastName: String = "Cohen"
}
let t = Test()
let mirror = Mirror(reflecting: t)
for child in mirror.children {
print(child.label ?? "")
}
print will be
name
lastName
This works:
struct s {
var x:Int = 1
var y:Int = 2
var z:Int = 3
}
var xyz = s()
let m = Mirror(reflecting: xyz)
print(m.description)
print(m.children.count)
for p in m.children {
print(p.label as Any)
}
I've come up with a swift solution, however unfortunately it doesn't work with Ints, Floats, and Doubles I believe.
func propertyNameFor(inout item : AnyObject) -> String{
let listMemAdd = unsafeAddressOf(item)
let propertyName = Mirror(reflecting: self).children.filter { (child: (label: String?, value: Any)) -> Bool in
if let value = child.value as? AnyObject {
return listMemAdd == unsafeAddressOf(value)
}
return false
}.flatMap {
return $0.label!
}.first ?? ""
return propertyName
}
var mutableObject : AnyObject = object
let propertyName = MyClass().propertyNameFor(&mutableObject)
It compares memory addresses for an object's properties and sees if any match.
The reason it doesn't work for Ints, Floats, and Doubles because they're not of type anyobject, although you can pass them as anyobject, when you do so they get converted to NSNumbers. therefore the memory address changes. they talk about it here.
For my app, it didn't hinder me at all because I only needed it for custom classes. So maybe someone will find this useful. If anyone can make this work with the other datatypes then that would be pretty cool.
Completing the accepted answer for extensions:
The property needs to be #objc.
var appId: String? {
....
}
You need to use #keyPath syntax, \ notation is not supported yet for extensions.
#keyPath(YourClass.appId)
The best solution is Here
From given link
import Foundation
extension NSObject {
//
// Retrieves an array of property names found on the current object
// using Objective-C runtime functions for introspection:
// https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/ObjCRuntimeGuide/Articles/ocrtPropertyIntrospection.html
//
func propertyNames() -> Array<String> {
var results: Array<String> = [];
// retrieve the properties via the class_copyPropertyList function
var count: UInt32 = 0;
var myClass: AnyClass = self.classForCoder;
var properties = class_copyPropertyList(myClass, &count);
// iterate each objc_property_t struct
for var i: UInt32 = 0; i < count; i++ {
var property = properties[Int(i)];
// retrieve the property name by calling property_getName function
var cname = property_getName(property);
// covert the c string into a Swift string
var name = String.fromCString(cname);
results.append(name!);
}
// release objc_property_t structs
free(properties);
return results;
}
}