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

• #fifth

  Returns the fifth element in an array.

• #fourth

  Returns the fourth element in an array.

• #from(position : Int)

  Returns the tail of the array from position.

• #in_groups(number, fill_with = nil)

  Splits or iterates over the array in number of groups, padding any remaining slots with fill_with unless it is false.

• #in_groups(number, fill_with = nil, &)
• #not_last

  Returns the elements in an array except the last one.

• #rest

  Returns the elements in an array except the first one.

• #second

  Returns the second element in an array.

• #slice(index : Int, length : Int) : Array(T)

  Array#slice(index : Int, length : Int)

• #slice(index : Int) : T

  Array#slice(index : Int)

• #slice(range : Range(Int, Int)) : Array(T)

  Array#slice(range : Range(Int, Int))

• #split(value = nil)

  Divides the array into one or more subarrays based on a delimiting value or the result of an optional block.

• #split(&)

  Divides the array into one or more subarrays based on a the result of an optional block.

• #third

  Returns the third element in an array.

• #to(position : Int)

  Returns the beginning of the array up to position.

• #to_param

  Calls #to_param on all its elements and joins the result with slashes.

• #to_query(namespace)

  Cast an array as a HTTP::Params and buils an url-encode string.

Instance Method Detail

[1, 2, 3, 4, 5].second
=> [5]

[1, 2, 3, 4, 5].second
=> [4]

  %w( a b c d ).from(0)
=> ["a", "b", "c", "d"]

  %w( a b c d ).from(2)
=> ["c", "d"]

  %w( a b c d ).from(10)
=> []

  %w().from(0)
=> []

  %w( a b c d ).from(-2)
=> ["c", "d"]

  %w( a b c ).from(-10)
=> []

  %w(1 2 3 4 5 6 7 8 9 10).in_groups(3) {|group| p group}
  ["1", "2", "3", "4"]
  ["5", "6", "7", nil]
  ["8", "9", "10", nil]

  %w(1 2 3 4 5 6 7 8 9 10).in_groups(3, ' ') {|group| p group}
  ["1", "2", "3", "4"]
  ["5", "6", "7", " "]
  ["8", "9", "10", " "]

  %w(1 2 3 4 5 6 7).in_groups(3, false) {|group| p group}
  ["1", "2", "3"]
  ["4", "5"]
  ["6", "7"]

[1, 2, 3, 4, 5].not_last
=> [1, 2, 3, 4]

[1, 2, 3, 4, 5].rest
=> [2, 3, 4, 5]

[1, 2, 3, 4, 5].second
=> [2]

[1, 2, 3, 4, 5].split(3)
=> [[1, 2], [4, 5]]

(1..10).to_a.split { |i| i % 3 == 0 }
=> [[1, 2], [4, 5], [7, 8], [10]]

[1, 2, 3, 4, 5].second
=> [3]

  %w( a b c d ).to(0)
=> ["a"]

  %w( a b c d ).to(2)
=> ["a", "b", "c"]

  %w( a b c d ).to(10)
=> ["a", "b", "c", "d"]

  %w().to(0)
=> []

  %w( a b c d ).to(-2)
=> ["a", "b", "c"]

  %w( a b c ).to(-10)
=> []

["michael", "jhon"].to_query("user")
=> "user%5B%5D=michael&user%5B%5D=jhon"