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iOS Swift Collections and Control Flow Introduction to Collections Adding Items to Arrays

Agustin Hernandez
Agustin Hernandez
2,747 Points

Creating Empty Arrays

What's the difference when declaring an empty array

          // like this
          var someArray: [SomeType]
          // Or like this
          var someArray = [SomeType]()

2 Answers

Alex Koumparos
Alex Koumparos
Python Development Techdegree Student 36,862 Points

In the first case:

var someArray: [SomeType]

You have declared but not initialised your array. If you wanted to use this style to declare an empty array, you would have written:

var someArray: [SomeType] = []

The second case:

var someArray = [SomeType]()

is exactly equivalent to var someArray: [SomeType] = []. The difference is purely personal style preference. Apple uses both in their own documentation, see here and here

First line is that you have declared your array but didn't assign anything (technically you just gave a name but no value)

Second line of code, you have named your array and assigned an empty/placeholder value in it.