Is there any easy way to merge two arrays in swift along with removing duplicates?

Simply :

let unique = Array(Set(a + b))

This is commonly called a union, which is possible in Swift using a Set:

let a = [1, 2, 3]
let b = [3, 4, 5]

let set = Set(a)
let union = set.union(b)

Then you can just convert the set into an array:

let result = Array(union)

Swift 4.0 Version

extension Array where Element : Equatable {

  public mutating func mergeElements<C : Collection>(newElements: C) where C.Iterator.Element == Element{
    let filteredList = newElements.filter({!self.contains($0)})
    self.append(contentsOf: filteredList)
  }

}

As mentioned: The array passed to the function is the array of object that will be omitted from the final array