Literals: Array

Array

An Array is a generic type containing elements of a type T. It is typically created with an array literal:

[1, 2, 3]         # Array(Int32)
[1, "hello", 'x'] # Array(Int32 | String | Char)

An Array can have mixed types, meaning T will be a union of types, but these are determined when the array is created, either by specifying T or by using an array literal. In the latter case, T will be set to the union of the array literal elements.

When creating an empty array you must always specify T:

[] of Int32 # same as Array(Int32).new
[]          # syntax error

Array of String

Arrays of strings can be created with a special syntax:

%w(one two three) # ["one", "two", "three"]

Array of Symbol

Arrays of symbols can be created with a special syntax:

%i(one two three) # [:one, :two, :three]

Array-like types

You can use a special array literal syntax with other types too, as long as they define an argless new method and a << method:

MyType{1, 2, 3}

If MyType is not generic, the above is equivalent to this:

tmp = MyType.new
tmp << 1
tmp << 2
tmp << 3
tmp

If MyType is generic, the above is equivalent to this:

tmp = MyType(typeof(1, 2, 3)).new
tmp << 1
tmp << 2
tmp << 3
tmp

In the case of a generic type, the type arguments can be specified too:

MyType(Int32 | String) {1, 2, "foo"}