CODEWITHSUNDEEP
swift
Crystal
Crystal

Reputation: 29518

Difference between [] and []() in Swift

I tried searching around for what this is

[]()

But I'm not really sure. In a playground, I did this:

var test = [Int]();
test.append(1);
test.append(2);

If I leave off the () and do

var test = [Int];
test.append(1);
test.append(2);

It still looks like an array of Ints to me. What is the difference?

Upvotes: 2

Views: 535

Answers (2)

matt
matt

Reputation: 535944

Type() means "call init()" - i.e., make a new instance of Type.

[Int] is a type, like String. [Int] means "array-of-Int".

String() makes a new empty String instance. [Int]() makes a new empty array-of-Int instance.

You can declare a variable as being of type array-of-Int. Or you can make and assign a new array-of-Int instance. Which is what you are doing here:

var test = [Int]()

But you cannot assign a type to a variable without further syntax. Thus, this is illegal:

var test = [Int]

EXTRA for experts

You can say:

var test = [Int].self

That does assign the type to the variable! That is unlikely to be what you want here, because now you have no array; you have a type, itself, as object!!

Upvotes: 5

Antonio
Antonio

Reputation: 72780

[Type] is syntactic sugar for Array<Type>, so it represents the array type, which is a generic struct, and for which you specify the type of elements it holds (Int in this example)

So the difference between:

[Int]

and

[Int]()

is the same as for

Array<Int>

and

Array<Int>()

The first is just a type, which you can use when declaring a variable or a function parameter.

The second invokes the parameterless constructor on that type, i.e. creates an instance of that type.

Upvotes: 0

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