Due to type erasure, actual generic arguments cannot be obtained through T::class token of a generic class. Different objects of a class must have the same class token, that’s why it cannot contain actual generic arguments. Edit: Since Kotlin 1.3.50, following the technique described below to get type information for a reified type parameter is … Read more
This can be achieved using protocol extensions (See The Swift Programming Language: Protocols for more information). To sum just Ints you could do: extension Sequence where Iterator.Element == Int { var sum: Int { return reduce(0, +) } } Usage: let nums = [1, 2, 3, 4] print(nums.sum) // Prints: “10” Or, for something more … Read more
min and max are defined in Swift: func max<T : Comparable>(x: T, y: T, rest: T…) -> T func min<T : Comparable>(x: T, y: T, rest: T…) -> T and used like so: let min = min(1, 2) let max = max(1, 2) See this great writeup on documented & undocumented built-in functions in Swift.
For a class with generic parameter T, you cannot do this because you have no type information for T since the JVM erases the type information. Therefore code like this cannot work: class Storage<T: Any> { val snapshot: Snapshot? = … fun retrieveSomething(): T? { return snapshot?.getValue(T::class.java) // ERROR “only classes can be used…” } … Read more
Only one upper bound can be specified inside the angle brackets. Kotlin offers different syntax for generic constraints when there is more than one constraint: class Foo<T>(val t: T) where T : Bar, T : Baz { … } and for functions: fun <T> f(): Foo where T : Bar, T : Baz { … … Read more
Workaround: You can create NSOperation subclass (no generic), override main and call you own ‘execute’ func, which can be overriden by generic subclasses. Example: class SwiftOperation : NSOperation { final override func main() { execute() } func execute() { } } class MyOperation<T> : SwiftOperation { override func execute() { println(“My operation main was called”) … Read more
No, it’s not possible. Dart static method invocations are resolved at compile-time, so it’s not possible to call them on type variables which only have a value at run-time. If it was possible, it would be completely unsafe. Anyone can create a class C extending A which does not have a static func member and … Read more
You can’t compare an arbitrary value to nil (EDIT: but see Sulthan’s comment below; it may be that we should be able to compare arbitrary values to nil; the rest of this paragraph may be true today, but only due to a compiler bug). While Optional has some bits of syntactic sugar applied to it, … Read more
It means that the trait is optional. The current syntax was introduced in the DST syntax RFC. The only trait I am aware of that works for ? is Sized. In this specific example, we can implement BorrowMut for unsized types, like [T] — note that there’s no & here! One built-in implementation makes use … Read more
As of TypeScript 2.3, you can use generic parameter defaults. private logData<T, S = {}>(operation: string, responseData: T, requestData?: S) { // your implementation here }