class Array(T)

• Array(T)
• Reference
• Object

Overview

An Array is an ordered, integer-indexed collection of objects of type T.

Array indexing starts at 0. A negative index is assumed to be relative to the end of the array: -1 indicates the last element, -2 is the next to last element, and so on.

An Array can be created using the usual new method (several are provided), or with an array literal:

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

See Array literals in the language reference.

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' types.

When creating an empty array you must always specify T:

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

An Array is implemented using an internal buffer of some capacity and is reallocated when elements are pushed to it when more capacity is needed. This is normally known as a dynamic array.

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

set = Set{1, 2, 3} # => Set{1, 2, 3}
set.class          # => Set(Int32)

The above is the same as this:

set = Set(typeof(1, 2, 3)).new
set << 1
set << 2
set << 3

Included Modules

• Comparable(Array(T))
• Indexable::Mutable(T)

Defined in:

Instance Method Summary

• #to_slice

  This is a convenience method for creating a Slice from an Array.

Instance Method Detail

Slice.new(array.size) { |idx| array[idx] }

# In a spec, you need a Slice of 10 elements.
[1, 2, 3, 5, 7, 11, 13, 17, 19, 23].to_slice

# In a spec, you have a method that is returning an array, but your original
# data is in a slice.
do_something_and_get_an_array.to_slice.should eq original_slice