"Empty Collection Literal Requires an Explicit Type" Error on Swift3
I Have a Variable on My Class: Var List = [] and I Use It on a Function of My Class: Func chargeData (Data: Nsarray){ List = Data } It Worked Well on My...
I have a variable on my class:
var list = []
and I use it on a function of my class:
func chargeData (data: NSArray){
list = data
}
It worked well on my project in Swift 2.3 but when I have updated it to XCode8 and Swift3 it gives to me the following error:
Empty collection literal requires an explicit type
so I have added a typecast to my list variable:
var list = [] as! NSArray
but it gives to me the following alert:
Forced cast of 'NSArray' to same type has no effect
I know that an alert does not broke the application but I would like to solve this error in a proper way.
Did someone got the same error and solved it properly?
Thanks in advance!
4 Answers
This error occurs since implicit conversions are abolished so you have to tell the compiler the explicit type (of the ArrayLiteral []):
var list: NSArray = []
// or
var list = [] as NSArray
The Swift 5 guided tour is pretty explicit about creating empty arrays or dictionaries: towards the end of the first section.
To create an empty array or dictionary, use the initializer syntax.
let emptyArray = [String]()
let emptyDictionary = [String: Float]()
Update swift 4 :
var array = [] as [String]
You are mixing ObjectiveC (NSArray) and Swift (Array<T>). Items inside an NSArray are assumed to be NSObject and its subclasses, while Swift has no clue what T is since the array is empty and hence type inference doesn't work.
If you declare it like this:
var data: NSArray = []
there will be a conflict since var means mutable in Swift, but NSArray is immutable in ObjC. You can get around that by changing it to NSMutableArray, which is a subclass of NSArray:
let data = NSMutableArray() // note that we don't need var here
// as NSMutableArray is already mutable
If you want to keep data as Swift's Array, give it a type:
var data = [MyDataModel]()
// or
var data = [AnyObject]()
// usage:
chargeData(data: data as NSArray)
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