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Swift - Variadic Parameters

Variadic Parameters make it possible to pass zero or more values of a specific type into a function.

In the following example, the add methods has one variadic parameter (i.e. _ newContent: Content...):

struct Content {
    let title: String
}

struct Bucket {
    private(set) var content: [Content] = []
    
    mutating func add(_ newContent: Content...) {
        content.append(contentsOf: newContent)
    }
}

To the add method, we can pass in 0, 1, or more parameter of type Content.

Add only a single content item:

var bucket = Bucket()
bucket.add(Content(title: "Blog post 1"))

Add multiple items:

bucket.add(Content(title: "Blog post 2"), Content(title: "Blog post 3"))

Array or Variadic Parameters?​

What is the difference between newContent: Content... and newContent: [Content]?

Under the hood, a variadic argument translates the list of parameter into an array. In fact, the add method implementation we did in the example, treats it as an array. We may boldly say that a variadic argument is only syntactic sugar.

Reference​

How to use Variadic parameters in Swift