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arraysswift
Vakas
Vakas

Reputation: 6452

Confused about Swift Array Declarations

Is there any difference between the following?

  1. var array1_OfStrings = [String]()

  2. var array2_OfStrings: [String] = []

  3. var array3_OfStrings: [String]

Testing in Playground shows that 1 and 2 are the same but 3 behaves differently. Can someone explain me the difference please? And also what will be the preferred way to declare an empty array of String?

Upvotes: 5

Views: 286

Answers (2)

Miknash
Miknash

Reputation: 7948

While I might be late to the party, there is one thing that needs to be said.

First option set array1_OfStrings to array of Strings

The other option tells that array1_OfStrings is array of Strings and then set it empty.

While this might be a really small difference, you will notice it while compiling. For the first option compiler will automatically try to find out what is the type of array1_OfStrings. Second option won't do that, you will let compiler know that this actually is array of Strings and done deal.

Why is this important? Take a look at the following link: https://thatthinginswift.com/debug-long-compile-times-swift/

As you can see, if you don't declare type of your variable that might impact build performance A LOT.

Upvotes: 4

zc246
zc246

Reputation: 1514

First two have the same effect.

  1. declare a variable array1_OfStrings, let it choose the type itself. When it sees [String](), it smartly knows that's type array of string.

  2. You set the variable array2_OfStrings as type array of string, then you say it's empty by []

  3. This is different because you just tell you want array3_OfStrings to be type array of string, but not given it an initial value.

I think the first one is recommended as The Swift Programming Language uses it more often.

Upvotes: 4

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