Swift - Custom Type Generic Structures

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Introduction

Generics apply to structures.

Consider the following implementation of a queue using a structure: 

struct MyGenericQueue < T > {
    var elements =  [T ]()
    var startIndex = 0

    mutating func queue(item:  T ) {
        elements.append(item)
    }

    mutating func dequeue() -> T! {
        if elements.isEmpty {
               return nil
           } else {
               return elements.removeAtIndex (0)
           }
    }
}

You can now use the MyGenericQueue structure for any specified data type:

Demo

struct MyGenericQueue < T > {
    var elements =  [T ]()
    var startIndex = 0

    mutating func queue(item:  T ) {
        elements.append(item)//  w  w  w . j  ava2 s  .c  om
    }

    mutating func dequeue() -> T! {
        if elements.isEmpty {
               return nil
           } else {
               return elements.removeAtIndex (0)
           }
    }
}
var myGenericQueue = MyGenericQueue<String>()
myGenericQueue.queue(item:"Hello")
myGenericQueue.queue(item:"Swift")
print(myGenericQueue.dequeue())  //Hello
print(myGenericQueue.dequeue())  //Swift
print(myGenericQueue.dequeue())  //nil

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