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"
Related
Today I come across a very strange situation while getting value from dictionary.I have made two cases here.
Case 1
if I write code below
let str = "{\"num\":2}"
var dict = convertToDictionary(text: str)!
if let num = dict["num"] as? Float {
print("Value is \(num)")
} else {
print("parse error")
}
func convertToDictionary(text: String) -> [String: Any]? {
if let data = text.data(using: .utf8) {
do {
return try JSONSerialization.jsonObject(with: data, options: []) as? [String: Any]
} catch {
print(error.localizedDescription)
}
}
return nil
}
As you can see value for key num is Integer but while fetching value from dictionary I expect value as Float. so it should go to else block but it prints the value.
Case 2
var test = 2
var dict:[String:Any] = [String:Any]()
dict["num"] = test
if let num = dict["num"] as? Float {
print("Value is \(num)")
} else {
print("parse error")
}
As I have not defined data type so by default it should be integer here & I expect value to be Float. This does work as I expect
Now here is does not print value it show the parse error
Please explain to me why this is happening ?
The answer is - dictionaries in those two cases are actually not identical.
In second case, the value of dict["num"] in of Int type, because you explicitly assigned an Int to it.
In first case however, you get a dictionary via JSONSerialization which turns numbers to NSNumber instances. So, the value of dict["num"] is of NSNumber type. And NSNumber initialized with an Int can be succesfuly cast to both Int and Float
In the first case you're creating json and inserting into dict which is getting the value in [String: Any] format. Here dict["num"] is in NSNumber format.
In the second case you created the dict with [String: Any] format but put the value as Int. var test = 2 this line makes variable test as Int and when you're inserting that value into dict with format [String: Any], it's taking the value of format Any as Int.
So basically in second case, dict["num"] is Int.
From Apple Doc, variable will take the datatype of the value it was assigned at the beginning.
That's why you can convert Any to Float at the first case but cannot convert Int to Float at the second.
If you try with var test: Float = 2, you'll get the value at the second case also.
try
if let num = dict["num"] as? NSNumber {
let floatValue = num.floatValue
print("Value is \(floatValue)")
} else {
print("parse error")
}
I have create class Testing model which has 4 dataMember it should not be null when accessing (means return default value)
extension Double {
/// Rounds the double to decimal places value
func roundTo(places:Int = 2) -> Double
{
let divisor = pow(10.00, Double(places))
return (self * divisor).rounded() / divisor
}
}
class TestingModel{
var id : String!
var name : String! = "abc" /*It is not working*/
var price : Double! = 0.00
var uniqueId : Int! = 1
/**
* Instantiate the instance using the passed dictionary values to set the properties values
*/
init(dictionary: [String:Any])
{
id = (dictionary["id"] as? String) ?? "" //I dont want to do like this way
name = dictionary["name"] as? String
price = (dictionary["price"] as? Double)?.roundTo() ?? 0.00
uniqueId = dictionary["unique_id"] as? Int
}
}
let t:TestingModel = TestingModel.init(dictionary: ["x id" : "x012y12345z45","x name":"test1","x price":100.0,"uniqueId":1236.0])
let testString = "Jd " + t.id
print(testString) //Perfect
print(t.name)
print(t.price) /* Only one decemal point is printed */
Getting Output
Jd
nil
0.0
Expected output
Jd
abc /Should return abc instead of nil/
0.00 /Two decimal point complulsury/
What i actually mean in
if i assign nil value to variable then it should remain with its default value without writing this Optional chaining ?? "abc" in constructor
price is a Double type and what you are asking to do is to print that double value to 2 decimal places. Then you should make use of the following.
let a = 0.0
print(String(format: "%.2f", a))
this prints:
0.00
If you are planning to round it to decimal places, then also the above code will return that. But if you need it to round and return a double type then you can check this answer
Based on your updated question, I suggest to use the model as follows:
class TestingModel{
var id : String = ""
var name : String = "abc"
var price : Double = 0.0
var uniqueId : Int = 1
/**
* Instantiate the instance using the passed dictionary values to set the properties values
*/
init(dictionary: [String:Any])
{
id = (dictionary["id"] as? String) ?? ""
name = dictionary["name"] as? String ?? "abc"
price = (dictionary["price"] as? Double) ?? 0.0
uniqueId = dictionary["unique_id"] as? Int ?? 1
}
}
You seem to have asked two different questions here. The first one regarding doubles have already been answered by adev. I will answer the second one, which is:
if i assign nil value to variable then it should remain with its default value without writing this Optional chaining ?? "abc" in constructor
If you want to do this then it means that the variable shouldn't be optional at all, as nil isn't one of its valid values. Make the variable a non-optional type and give it a default value.
class TestingModel{
var id : String = ""
var name : String = "abc"
var price : Double = 0.00
var uniqueId : Int = 1
}
You can't really avoid using ?? in the constructor because of the nature of dictionaries. They will always return a nil value if the key does not exist. You have to check it. It does not make sense even if this is possible anyway. Imagine something like this:
someVariable = nil // someVariable is now 0
This is extremely confusing. someVariable is 0, even though it appears that nil is assigned to it.
A workaround will be to add a dictionary extension. Something like this:
extension Dictionary {
func value(forKey key: Key, defaultValue: Value) -> Value {
return self[key] ?? defaultValue
}
}
But I still recommend that you use ?? instead.
The following works in Playground:
func stringToInt(numberStr: String!) -> Int {
print(numberStr)
return Int(numberStr)!
}
let strNum1: String?
strNum1 = "1"
let result = stringToInt(numberStr: strNum1)
It returns 1 as expected.
In Xcode, a similar approach fails:
func stringToInt(numberStr: String!) -> Int {
print("\(numberStr!)")
let str = "\(numberStr!)"
print(Int(str))
return Int(str)!
}
The first print produces: Optional(1)
The second print produces: nil
The return statement fails because it is attempting to create an Int from a nil.
It must be something simple but I haven't been able to determine why it's not working. This is in Swift 3 and Xcode 8 BTW.
#Hamish:
In Xcode, I have a string with a numeric value. This:
print("number: (selectedAlertNumber) - unit: (selectedAlertUnit)")
...produces this:
number: Optional(1) - unit: Day
Then, I'm checking to see if either selectedAlertNumber of selecterAlertUnit != "-"
if selectedAlertNumber != "-" && selectedAlertUnit != "-" {
// set alert text
var unitStr = selectedAlertUnit
let alertNumber = stringToInt(numberStr: selectedAlertNumber)
if alertNumber > 1 {
unitStr.append("s")
}
let alertText = "...\(selectedAlertNumber) \(unitStr) before event."
alertTimeCell.setAlertText(alertText: alertText)
// set alert date/time
}
The let alertNumber = stringToInt... line is how I'm calling the function. I could just attempt the conversion there but I wanted to isolate the problem by wrapping the conversion in it's own function.
Using string interpolation to convert values to a String is usually not advised since the output may differ depending on optional status of the value. For example, consider these two functions:
func stringToInt(numberStr: String!) -> Int
{
print("\(numberStr!)")
let str = "\(numberStr!)"
return Int(str)!
}
func otherStringToInt(numberStr: String!) -> Int
{
print(numberStr)
let str = "\(numberStr)"
return Int(str)!
}
The only difference between these two is the ! in the second function when using string interpolation to get a String type value from numberStr. To be more specific, at the same line in function 1 compared to function 2, the string values are very different depending on whether or not the interpolated value is optional:
let str1: String = "1"
let str2: String! = "1"
let str3: String? = "1"
let otherStr1 = "\(str1)" // value: "1"
let otherStr2 = "\(str2)" // value: "Optional(1)"
let otherStr3 = "\(str2!)" // value: "1"
let otherStr4 = "\(str3)" // value: "Optional(1)"
let otherStr5 = "\(str3!)" // value: "1"
Passing otherStr2 or otherStr4 into the Int initializer will produce nil, since the string "Optional(1)" is not convertible to Int. Additionally, this will cause an error during the force unwrap. Instead of using string interpolation in your function, it would be better to just use the value directly since it's already a String.
func stringToInt(numberStr: String!) -> Int
{
return Int(numberStr)!
}
Let me know if this makes sense.
Also, my own personal feedback: watch out force unwrapping so frequently. In many cases, you're running the risk of getting an error while unwrapping a nil optional.
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 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.