I have a value returned in a string (numbers separated by commas) and I'd like to make a Date object out of it. It looks like this is not possible, can someone confirm and/or suggest me a solution.
This does not work :
let dateString='2017,3,22,0';
let dateFromString = new Date(dateString);
This works though (when I pass a list of numbers) :
let dateFromString = new Date(2017,3,22,0);
And this works also :
let dateString = '2008/05/10 12:08:20';
let dateFromString = new Date(dateString);
The goal would be to create a Date object from a uniform string. Is that possible ?
Can I create a Date object from a predefined string, which has only one type of separator (comma, colon, slash or whatever) ?
If your environment is compatible with ES6 (eg. Babel, TypeScript, modern Chrome/Firefox etc), you can use the string's .split(',') and decompose the array into arguments like the following:
const dateString = '2017,3,22,0';
const date = new Date(...dateString.split(',')); // date object for 2017/03/22
ES5 compatible version:
var dateString = '2017,1,2,0';
var date = new (Function.prototype.bind.apply(Date, [null].concat(dateString.split(','))));
As for how the .bind.apply method works with new, you can take a look at Use of .apply() with 'new' operator. Is this possible?
Note: Thanks to the two comments below for spotting my errors 👍
Related
i am new to kotlin.
In swift i can do :
let endpoint = "categories/" + "%#/issues/"
let number = "4"
let finalstring = String(format: endpoint, number)
The final output of the string will be : categories/4/issues/ as a string .
I have looked at string format in kotlin but it's only work afterwards meaning that i can't define a template for my string and fill it later.
var value1 = "categories/"
var value2 = 4
var value3 = "/issues/"
println(java.lang.String.format("%s%d%s", value1, value2, value3))
This give me the same result but it's mean that i have to manualy write the end of the string.
What i want to do i to have a template for my string in a Road file.
Then complet my string at the run time. The probleme is that the part of my string that i want to complete is in the middle of the string.
Of course i can use substring and remplace but i am looking for a clean way to do it as in swift.
Thanks for helping.
One possible option would be to define a local function that does the formatting:
fun requestString(number: Int) = "categories/$number/issues/"
val finalString = requestString(4)
You can create your format string up front with all the constant parts, and with relevant placeholders (like %d for numbers) (more info in the javadoc).
Later, use the regular Java String.format() later with the parameters:
// define this constant up front
val format = "categories/%d/issues/"
// and then later:
val categoryId = 4
println(String.format(format, categoryId))
You already have the answer right there in your example, you just have to put it together.
String.format takes %s as placeholder for a String or %d for a number (and many more placeholder options).
So your template string would be: "categories/%d/issues/". To format it you use:
val format = "categories/%d/issues/"
val number = 4
val string = String.format(format, number)
About interpolation vs formatting, they can be used in different situations.
If you have the template string available in source code then you would use interpolation:
val string = "categories/${category.id}/issues/"
But when you have no control over the string, because it comes from an external source (such as a file), then you would have to use the formatting.
I am trying to build a table of current locale properties in code, and have encountered issues with trying to pass the value of a variable to a function:
let currentLocale = Locale(identifier: "en_US")
let calendar1 = currentLocale.calendar // "gregorian (fixed)"
let propertyName = "calendar"
let calendar2 = currentLocale.propertyName // Error: Value of type 'Locale' has no member 'porpertyName'
In the last line of code above, the instance of Locale thinks I am passing it "propertyName" rather than the contents of the variable "calendar".
Is there any way to pass the value of propertyName ("calendar") to the instance of Locale? I know that in other languages, you can prepend the variable name like '$propertyName', and that tells it to read the value of the variable.
I want to keep this pure Swift if possible.
You are looking for some form of key-value coding.
It's a little tricky, in that this is a purely Objective-C feature of Cocoa, so it doesn't work with the Swift overlay class Locale; you will have to cast currentLocale to Objective-C NSLocale. Moreover, NSLocale exposes its attributes through special NSLocale.Key types. After a great deal of casting, I find that this works:
let calendar2 =
(currentLocale as NSLocale).object(forKey:NSLocale.Key(rawValue:propertyName))
calendar2 is typed as Any but you can cast it down to a String.
I have an object from the server that is recognized by Swift 2.1 as either NSDate or NSNull. I want to put it into a struct with a property of type NSDate.
Is that possible? If not, how should I handle this to be type safe later when I use it?
struct Data {
var completedAt: [NSDate]
var name: [String]
var gender: [Bool]
}
but sometimes completedAt comes from the server as NSNull:
completedAt = "<null>";
Any help is very much appreciated, thank you.
Based on my interpretation of the text in the question you didn't mean to declare the variables as arrays.
This is how I handle my parson and I think it works pretty neatly.
The date formatter should probable not be initiated in every iteration of the constructor. If you won't use the date regularly you might want to keep the detesting until you need to parse the date or you can have a static date formatter utility that you only instantiate once.
struct Data {
var completedAt: NSDate?
var name: String
var gender: Bool
init?(dictionary: [String:AnyObject]) {
//Guessing that you want some of the values non optional...
guard let name = dictionary["name"] as? String,
let gender = dictionary["gender"] as? String
else {
return nil
}
self.name = name
self.gender = gender
let dateFormatter = NSDateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss"
//safe handle of optional values
if let completedAtString = dictionary["completedAt"] as? String, completedAt = dateFormater.dateFromString(completedAtString) {
self.completedAt = completedAt
}
}
}
Take a step back. For each item that the server might provide, there is no guarantee whatsoever that you receive what you expect, since you cannot control the server. So you need to decide how to react to which input.
In the case of expecting a date for example (if your data comes in JSON, that means you likely expect a string formatted in a certain way), the actual data that you receive might be an array, dictionary, string, number, bool, null, or nothing. You might then for example decide that you want to interpret nothing or null or an empty string as nil, that you want to interpret a string containing a well-formatted date as an NSDate, and anything else a fatal error in a debug version, and as either nothing or a fatal error in a release version. On the other hand, if an NSDate is absolutely required then you might interpret anything that doesn't give an NSDate as an error.
Then you write a function that delivers exactly what you want and use it. That way you can parse complex data, with your code warning you when something isn't as it should be, and with your code either surviving any possible input, or deliberately crashing on wrong input, as you want it.
I want to be able to get the current time as a decimal point number so it can be used. so for example if the time is 13:46 I want to get it as 13.46
It seems simple but I am struggling getting to it.
We can use an NSDateFormatter to do exactly this:
extension NSDate {
func currentTime() -> String {
let formatter = NSDateFormatter()
formatter.dateFormat = "HH.mm"
return formatter.stringFromDate(self)
}
}
And now we just use it by calling it on any instance of NSDate:
let now = NSDate()
print(now.currentTime())
you can stringify the time and serch lastindexOf(":") and substitue it with a "."
UPDATE
I don't really catch what program language are you using, but it's plenty of library for stringify object so if you have a 13:46 you can convert it to String and, in the same string library you could find the method lastIndexOf(char). But if you don't find it you can always write following this concepts:
String are an array of Char so you can cycle it and convert the char in that position in the char you need.
I want to pass a string to DDMathParser and store answer in another string variable using swift. I am totally new to iOS platform so I dont really know syntax of functions. Example:
var expr = "5+9*2" //Some Expression
var result = DDMathParser.evaluate(expr) // Result of Expression
Here is a simple example how to use DDMathParser from Swift:
let expr = "5+9*2" as NSString
let result = expr.numberByEvaluatingString().integerValue
println(result) // 23
If you need floating point results then replace integerValue
by doubleValue.