An Array object is an ordered, integer-indexed collection of objects, called elements; the object represents an array data structure.
An element may be any object (even another array); elements may be any mixture of objects of different types.
Important data structures that use arrays include:
There are also array-like data structures:
Associative array (see Hash).
Environment (see ENV).
Array indexing starts at 0, as in C or Java.
A non-negative index is an offset from the first element:
Index 0 indicates the first element.
Index 1 indicates the second element.
…
A negative index is an offset, backwards, from the end of the array:
Index -1 indicates the last element.
Index -2 indicates the next-to-last element.
…
A non-negative index is in range if and only if it is smaller than the size of the array. For a 3-element array:
Indexes 0 through 2 are in range.
Index 3 is out of range.
A negative index is in range if and only if its absolute value is not larger than the size of the array. For a 3-element array:
Indexes -1 through -3 are in range.
Index -4 is out of range.
Although the effective index into an array is always an integer, some methods (both within class Array and elsewhere) accept one or more non-integer arguments that are integer-convertible objects.
You can create an Array object explicitly with:
An array literal:
[1, 'one', :one, [2, 'two', :two]]
A array literal:
%w[foo bar baz] # => ["foo", "bar", "baz"] %w[1 % *] # => ["1", "%", "*"]
A array literal:
%i[foo bar baz] # => [:foo, :bar, :baz] %i[1 % *] # => [:"1", :%, :*]
Array(["a", "b"]) # => ["a", "b"] Array(1..5) # => [1, 2, 3, 4, 5] Array(key: :value) # => [[:key, :value]] Array(nil) # => [] Array(1) # => [1] Array({:a => "a", :b => "b"}) # => [[:a, "a"], [:b, "b"]]
Array.new # => [] Array.new(3) # => [nil, nil, nil] Array.new(4) {Hash.new} # => [{}, {}, {}, {}] Array.new(3, true) # => [true, true, true]
Note that the last example above populates the array with references to the same object. This is recommended only in cases where that object is a natively immutable object such as a symbol, a numeric, nil, true, or false.
Another way to create an array with various objects, using a block; this usage is safe for mutable objects such as hashes, strings or other arrays:
Array.new(4) {|i| i.to_s } # => ["0", "1", "2", "3"]
Here is a way to create a multi-dimensional array:
Array.new(3) {Array.new(3)} # => [[nil, nil, nil], [nil, nil, nil], [nil, nil, nil]]
A number of Ruby methods, both in the core and in the standard library, provide instance method to_a, which converts an object to an array.
Benchmark::Tms#to_a
CSV::Table#to_a
Gem::List#to_a
Racc::ISet#to_a
Rinda::RingFinger#to_a
Ripper::Lexer::Elem#to_a
In addition to the methods it mixes in through the Enumerable module, class Array has proprietary methods for accessing, searching and otherwise manipulating arrays.
Some of the more common ones are illustrated below.
Elements in an array can be retrieved using the Array#[] method. It can take a single integer argument (a numeric index), a pair of arguments (start and length) or a range. Negative indices start counting from the end, with -1 being the last element.
arr = [1, 2, 3, 4, 5, 6] arr[2] #=> 3 arr[100] #=> nil arr[-3] #=> 4 arr[2, 3] #=> [3, 4, 5] arr[1..4] #=> [2, 3, 4, 5] arr[1..-3] #=> [2, 3, 4]
Another way to access a particular array element is by using the at method
arr.at(0) #=> 1
The slice method works in an identical manner to Array#[].
To raise an error for indices outside of the array bounds or else to provide a default value when that happens, you can use fetch.
arr = ['a', 'b', 'c', 'd', 'e', 'f'] arr.fetch(100) #=> IndexError: index 100 outside of array bounds: -6...6 arr.fetch(100, "oops") #=> "oops"
The special methods first and last will return the first and last elements of an array, respectively.
arr.first #=> 1 arr.last #=> 6
To return the first n elements of an array, use take
arr.take(3) #=> [1, 2, 3]
drop does the opposite of take, by returning the elements after n elements have been dropped:
arr.drop(3) #=> [4, 5, 6]
An array keeps track of its own length at all times. To query an array about the number of elements it contains, use length, count or size.
browsers = ['Chrome', 'Firefox', 'Safari', 'Opera', 'IE'] browsers.length #=> 5 browsers.count #=> 5
To check whether an array contains any elements at all
browsers.empty? #=> false
To check whether a particular item is included in the array
browsers.include?('Konqueror') #=> false
Items can be added to the end of an array by using either push or <<
arr = [1, 2, 3, 4] arr.push(5) #=> [1, 2, 3, 4, 5] arr << 6 #=> [1, 2, 3, 4, 5, 6]
unshift will add a new item to the beginning of an array.
arr.unshift(0) #=> [0, 1, 2, 3, 4, 5, 6]
With insert you can add a new element to an array at any position.
arr.insert(3, 'apple') #=> [0, 1, 2, 'apple', 3, 4, 5, 6]
Using the insert method, you can also insert multiple values at once:
arr.insert(3, 'orange', 'pear', 'grapefruit') #=> [0, 1, 2, "orange", "pear", "grapefruit", "apple", 3, 4, 5, 6]
The method pop removes the last element in an array and returns it:
arr = [1, 2, 3, 4, 5, 6] arr.pop #=> 6 arr #=> [1, 2, 3, 4, 5]
To retrieve and at the same time remove the first item, use shift:
arr.shift #=> 1 arr #=> [2, 3, 4, 5]
To delete an element at a particular index:
arr.delete_at(2) #=> 4 arr #=> [2, 3, 5]
To delete a particular element anywhere in an array, use delete:
arr = [1, 2, 2, 3] arr.delete(2) #=> 2 arr #=> [1,3]
A useful method if you need to remove nil values from an array is compact:
arr = ['foo', 0, nil, 'bar', 7, 'baz', nil] arr.compact #=> ['foo', 0, 'bar', 7, 'baz'] arr #=> ['foo', 0, nil, 'bar', 7, 'baz', nil] arr.compact! #=> ['foo', 0, 'bar', 7, 'baz'] arr #=> ['foo', 0, 'bar', 7, 'baz']
Another common need is to remove duplicate elements from an array.
It has the non-destructive uniq, and destructive method uniq!
arr = [2, 5, 6, 556, 6, 6, 8, 9, 0, 123, 556] arr.uniq #=> [2, 5, 6, 556, 8, 9, 0, 123]
Like all classes that include the Enumerable module, class Array has an each method, which defines what elements should be iterated over and how. In case of Array#each, all elements in self are yielded to the supplied block in sequence.
Note that this operation leaves the array unchanged.
arr = [1, 2, 3, 4, 5] arr.each {|a| print a -= 10, " "} # prints: -9 -8 -7 -6 -5 #=> [1, 2, 3, 4, 5]
Another sometimes useful iterator is reverse_each which will iterate over the elements in the array in reverse order.
words = %w[first second third fourth fifth sixth] str = "" words.reverse_each {|word| str += "#{word} "} p str #=> "sixth fifth fourth third second first "
The map method can be used to create a new array based on the original array, but with the values modified by the supplied block:
arr.map {|a| 2*a} #=> [2, 4, 6, 8, 10] arr #=> [1, 2, 3, 4, 5] arr.map! {|a| a**2} #=> [1, 4, 9, 16, 25] arr #=> [1, 4, 9, 16, 25]
Elements can be selected from an array according to criteria defined in a block. The selection can happen in a destructive or a non-destructive manner. While the destructive operations will modify the array they were called on, the non-destructive methods usually return a new array with the selected elements, but leave the original array unchanged.
arr = [1, 2, 3, 4, 5, 6] arr.select {|a| a > 3} #=> [4, 5, 6] arr.reject {|a| a < 3} #=> [3, 4, 5, 6] arr.drop_while {|a| a < 4} #=> [4, 5, 6] arr #=> [1, 2, 3, 4, 5, 6]
select! and reject! are the corresponding destructive methods to select and reject
Similar to select vs. reject, delete_if and keep_if have the exact opposite result when supplied with the same block:
arr.delete_if {|a| a < 4} #=> [4, 5, 6] arr #=> [4, 5, 6] arr = [1, 2, 3, 4, 5, 6] arr.keep_if {|a| a < 4} #=> [1, 2, 3] arr #=> [1, 2, 3]
First, what’s elsewhere. Class Array:
Inherits from class Object.
Includes module Enumerable, which provides dozens of additional methods.
Here, class Array provides methods that are useful for:
::[]: Returns a new array populated with given objects.
::new: Returns a new array.
::try_convert: Returns a new array created from a given object.
See also Creating Arrays.
all?: Returns whether all elements meet a given criterion.
any?: Returns whether any element meets a given criterion.
count: Returns the count of elements that meet a given criterion.
empty?: Returns whether there are no elements.
find_index (aliased as index): Returns the index of the first element that meets a given criterion.
hash: Returns the integer hash code.
include?: Returns whether any element == a given object.
none?: Returns whether no element == a given object.
one?: Returns whether exactly one element == a given object.
rindex: Returns the index of the last element that meets a given criterion.
<=>: Returns -1, 0, or 1, as self is less than, equal to, or greater than a given object.
==: Returns whether each element in self is == to the corresponding element in a given object.
eql?: Returns whether each element in self is eql? to the corresponding element in a given object.
These methods do not modify self.
[] (aliased as slice): Returns consecutive elements as determined by a given argument.
assoc: Returns the first element that is an array whose first element == a given object.
at: Returns the element at a given offset.
bsearch: Returns an element selected via a binary search as determined by a given block.
bsearch_index: Returns the index of an element selected via a binary search as determined by a given block.
compact: Returns an array containing all non-nil elements.
dig: Returns the object in nested objects that is specified by a given index and additional arguments.
drop: Returns trailing elements as determined by a given index.
drop_while: Returns trailing elements as determined by a given block.
fetch: Returns the element at a given offset.
fetch_values: Returns elements at given offsets.
first: Returns one or more leading elements.
last: Returns one or more trailing elements.
max: Returns one or more maximum-valued elements, as determined by #<=> or a given block.
min: Returns one or more minimum-valued elements, as determined by #<=> or a given block.
minmax: Returns the minimum-valued and maximum-valued elements, as determined by #<=> or a given block.
rassoc: Returns the first element that is an array whose second element == a given object.
reject: Returns an array containing elements not rejected by a given block.
reverse: Returns all elements in reverse order.
rotate: Returns all elements with some rotated from one end to the other.
sample: Returns one or more random elements.
select (aliased as filter): Returns an array containing elements selected by a given block.
shuffle: Returns elements in a random order.
sort: Returns all elements in an order determined by #<=> or a given block.
take: Returns leading elements as determined by a given index.
take_while: Returns leading elements as determined by a given block.
uniq: Returns an array containing non-duplicate elements.
values_at: Returns the elements at given offsets.
These methods add, replace, or reorder elements in self.
<<: Appends an element.
[]=: Assigns specified elements with a given object.
concat: Appends all elements from given arrays.
fill: Replaces specified elements with specified objects.
flatten!: Replaces each nested array in self with the elements from that array.
initialize_copy (aliased as replace): Replaces the content of self with the content of a given array.
insert: Inserts given objects at a given offset; does not replace elements.
reverse!: Replaces self with its elements reversed.
rotate!: Replaces self with its elements rotated.
shuffle!: Replaces self with its elements in random order.
sort!: Replaces self with its elements sorted, as determined by #<=> or a given block.
sort_by!: Replaces self with its elements sorted, as determined by a given block.
Each of these methods removes elements from self:
clear: Removes all elements.
compact!: Removes all nil elements.
delete: Removes elements equal to a given object.
delete_at: Removes the element at a given offset.
delete_if: Removes elements specified by a given block.
keep_if: Removes elements not specified by a given block.
pop: Removes and returns the last element.
reject!: Removes elements specified by a given block.
select! (aliased as filter!): Removes elements not specified by a given block.
shift: Removes and returns the first element.
slice!: Removes and returns a sequence of elements.
uniq!: Removes duplicates.
&: Returns an array containing elements found both in self and a given array.
+: Returns an array containing all elements of self followed by all elements of a given array.
-: Returns an array containing all elements of self that are not found in a given array.
|: Returns an array containing all element of self and all elements of a given array, duplicates removed.
difference: Returns an array containing all elements of self that are not found in any of the given arrays..
intersection: Returns an array containing elements found both in self and in each given array.
product: Returns or yields all combinations of elements from self and given arrays.
reverse: Returns an array containing all elements of self in reverse order.
union: Returns an array containing all elements of self and all elements of given arrays, duplicates removed.
combination: Calls a given block with combinations of elements of self; a combination does not use the same element more than once.
cycle: Calls a given block with each element, then does so again, for a specified number of times, or forever.
each: Passes each element to a given block.
each_index: Passes each element index to a given block.
permutation: Calls a given block with permutations of elements of self; a permutation does not use the same element more than once.
repeated_combination: Calls a given block with combinations of elements of self; a combination may use the same element more than once.
repeated_permutation: Calls a given block with permutations of elements of self; a permutation may use the same element more than once.
reverse_each: Passes each element, in reverse order, to a given block.
collect (aliased as map): Returns an array containing the block return-value for each element.
collect! (aliased as map!): Replaces each element with a block return-value.
flatten: Returns an array that is a recursive flattening of self.
inspect (aliased as to_s): Returns a new String containing the elements.
join: Returns a newsString containing the elements joined by the field separator.
to_a: Returns self or a new array containing all elements.
to_ary: Returns self.
to_h: Returns a new hash formed from the elements.
transpose: Transposes self, which must be an array of arrays.
zip: Returns a new array of arrays containing self and given arrays.
*: Returns one of the following:
With integer argument n, a new array that is the concatenation of n copies of self.
With string argument field_separator, a new string that is equivalent to join(field_separator).
pack: Packs the elements into a binary sequence.
sum: Returns a sum of elements according to either + or a given block.
Returns an array converted from object.
Tries to convert object to an array using to_ary first and to_a second:
Array([0, 1, 2]) # => [0, 1, 2] Array({foo: 0, bar: 1}) # => [[:foo, 0], [:bar, 1]] Array(0..4) # => [0, 1, 2, 3, 4]
Returns object in an array, [object], if object cannot be converted:
Array(:foo) # => [:foo]
Returns a new array that is self as a transposed matrix:
a = [[:a0, :a1], [:b0, :b1], [:c0, :c1]] a.transpose # => [[:a0, :b0, :c0], [:a1, :b1, :c1]]
The elements of self must all be the same size.
Related: see Methods for Converting.
Removes all elements from self; returns self:
a = [:foo, 'bar', 2] a.clear # => []
Related: see Methods for Deleting.
Returns the first element ele in self such that ele is an array and ele[1] == object:
a = [{foo: 0}, [2, 4], [4, 5, 6], [4, 5]] a.rassoc(4) # => [2, 4] a.rassoc(5) # => [4, 5, 6]
Returns nil if no such element is found.
Related: Array#assoc; see also Methods for Fetching.
Returns the element from self found by a binary search, or nil if the search found no suitable element.
See Binary Searching.
Related: see Methods for Fetching.
Returns self.
Returns the integer index of the element from self found by a binary search, or nil if the search found no suitable element.
See Binary Searching.
Related: see Methods for Fetching.
Returns a new array, populated with the given objects:
Array[1, 'a', /^A/] # => [1, "a", /^A/] Array[] # => [] Array.[](1, 'a', /^A/) # => [1, "a", /^A/]
Related: see Methods for Creating an Array.
Returns a new array.
With no block and no argument given, returns a new empty array:
Array.new # => []
With no block and array argument given, returns a new array with the same elements:
Array.new([:foo, 'bar', 2]) # => [:foo, "bar", 2]
With no block and integer argument given, returns a new array containing that many instances of the given default_value:
Array.new(0) # => [] Array.new(3) # => [nil, nil, nil] Array.new(2, 3) # => [3, 3]
With a block given, returns an array of the given size; calls the block with each index in the range (0...size); the element at that index in the returned array is the blocks return value:
Array.new(3) {|index| "Element #{index}" } # => ["Element 0", "Element 1", "Element 2"]
A common pitfall for new Rubyists is providing an expression as default_value:
array = Array.new(2, {}) array # => [{}, {}] array[0][:a] = 1 array # => [{a: 1}, {a: 1}], as array[0] and array[1] are same object
If you want the elements of the array to be distinct, you should pass a block:
array = Array.new(2) { {} } array # => [{}, {}] array[0][:a] = 1 array # => [{a: 1}, {}], as array[0] and array[1] are different objects
Raises TypeError if the first argument is not either an array or an integer-convertible object). Raises ArgumentError if the first argument is a negative integer.
Related: see Methods for Creating an Array.
Returns the new string formed by calling method #inspect on each array element:
a = [:foo, 'bar', 2] a.inspect # => "[:foo, \"bar\", 2]"
Related: see Methods for Converting.
Returns whether both:
self and other_array are the same size.
Their corresponding elements are the same; that is, for each index i in (0...self.size), self[i] == other_array[i].
Examples:
[:foo, 'bar', 2] == [:foo, 'bar', 2] # => true [:foo, 'bar', 2] == [:foo, 'bar', 2.0] # => true [:foo, 'bar', 2] == [:foo, 'bar'] # => false # Different sizes. [:foo, 'bar', 2] == [:foo, 'bar', 3] # => false # Different elements.
This method is different from method Array#eql?, which compares elements using Object#eql?.
Related: see Methods for Comparing.
Returns true if self and other_array are the same size, and if, for each index i in self, self[i].eql?(other_array[i]):
a0 = [:foo, 'bar', 2] a1 = [:foo, 'bar', 2] a1.eql?(a0) # => true
Otherwise, returns false.
This method is different from method Array#==, which compares using method Object#==.
Related: see Methods for Querying.
Returns the integer hash value for self.
Two arrays with the same content will have the same hash value (and will compare using eql?):
['a', 'b'].hash == ['a', 'b'].hash # => true ['a', 'b'].hash == ['a', 'c'].hash # => false ['a', 'b'].hash == ['a'].hash # => false
Returns elements from self; does not modify self.
In brief:
a = [:foo, 'bar', 2] # Single argument index: returns one element. a[0] # => :foo # Zero-based index. a[-1] # => 2 # Negative index counts backwards from end. # Arguments start and length: returns an array. a[1, 2] # => ["bar", 2] a[-2, 2] # => ["bar", 2] # Negative start counts backwards from end. # Single argument range: returns an array. a[0..1] # => [:foo, "bar"] a[0..-2] # => [:foo, "bar"] # Negative range-begin counts backwards from end. a[-2..2] # => ["bar", 2] # Negative range-end counts backwards from end.
When a single integer argument index is given, returns the element at offset index:
a = [:foo, 'bar', 2] a[0] # => :foo a[2] # => 2 a # => [:foo, "bar", 2]
If index is negative, counts backwards from the end of self:
a = [:foo, 'bar', 2] a[-1] # => 2 a[-2] # => "bar"
If index is out of range, returns nil.
When two Integer arguments start and length are given, returns a new array of size length containing successive elements beginning at offset start:
a = [:foo, 'bar', 2] a[0, 2] # => [:foo, "bar"] a[1, 2] # => ["bar", 2]
If start + length is greater than self.length, returns all elements from offset start to the end:
a = [:foo, 'bar', 2] a[0, 4] # => [:foo, "bar", 2] a[1, 3] # => ["bar", 2] a[2, 2] # => [2]
If start == self.size and length >= 0, returns a new empty array.
If length is negative, returns nil.
When a single Range argument range is given, treats range.min as start above and range.size as length above:
a = [:foo, 'bar', 2] a[0..1] # => [:foo, "bar"] a[1..2] # => ["bar", 2]
Special case: If range.start == a.size, returns a new empty array.
If range.end is negative, calculates the end index from the end:
a = [:foo, 'bar', 2] a[0..-1] # => [:foo, "bar", 2] a[0..-2] # => [:foo, "bar"] a[0..-3] # => [:foo]
If range.start is negative, calculates the start index from the end:
a = [:foo, 'bar', 2] a[-1..2] # => [2] a[-2..2] # => ["bar", 2] a[-3..2] # => [:foo, "bar", 2]
If range.start is larger than the array size, returns nil.
a = [:foo, 'bar', 2] a[4..1] # => nil a[4..0] # => nil a[4..-1] # => nil
When a single Enumerator::ArithmeticSequence argument aseq is given, returns an array of elements corresponding to the indexes produced by the sequence.
a = ['--', 'data1', '--', 'data2', '--', 'data3'] a[(1..).step(2)] # => ["data1", "data2", "data3"]
Unlike slicing with range, if the start or the end of the arithmetic sequence is larger than array size, throws RangeError.
a = ['--', 'data1', '--', 'data2', '--', 'data3'] a[(1..11).step(2)] # RangeError (((1..11).step(2)) out of range) a[(7..).step(2)] # RangeError (((7..).step(2)) out of range)
If given a single argument, and its type is not one of the listed, tries to convert it to Integer, and raises if it is impossible:
a = [:foo, 'bar', 2] # Raises TypeError (no implicit conversion of Symbol into Integer): a[:foo]
Related: see Methods for Fetching.
Assigns elements in self, based on the given object; returns object.
In brief:
a_orig = [:foo, 'bar', 2] # With argument index. a = a_orig.dup a[0] = 'foo' # => "foo" a # => ["foo", "bar", 2] a = a_orig.dup a[7] = 'foo' # => "foo" a # => [:foo, "bar", 2, nil, nil, nil, nil, "foo"] # With arguments start and length. a = a_orig.dup a[0, 2] = 'foo' # => "foo" a # => ["foo", 2] a = a_orig.dup a[6, 50] = 'foo' # => "foo" a # => [:foo, "bar", 2, nil, nil, nil, "foo"] # With argument range. a = a_orig.dup a[0..1] = 'foo' # => "foo" a # => ["foo", 2] a = a_orig.dup a[6..50] = 'foo' # => "foo" a # => [:foo, "bar", 2, nil, nil, nil, "foo"]
When Integer argument index is given, assigns object to an element in self.
If index is non-negative, assigns object the element at offset index:
a = [:foo, 'bar', 2] a[0] = 'foo' # => "foo" a # => ["foo", "bar", 2]
If index is greater than self.length, extends the array:
a = [:foo, 'bar', 2] a[7] = 'foo' # => "foo" a # => [:foo, "bar", 2, nil, nil, nil, nil, "foo"]
If index is negative, counts backwards from the end of the array:
a = [:foo, 'bar', 2] a[-1] = 'two' # => "two" a # => [:foo, "bar", "two"]
When Integer arguments start and length are given and object is not an array, removes length - 1 elements beginning at offset start, and assigns object at offset start:
a = [:foo, 'bar', 2] a[0, 2] = 'foo' # => "foo" a # => ["foo", 2]
If start is negative, counts backwards from the end of the array:
a = [:foo, 'bar', 2] a[-2, 2] = 'foo' # => "foo" a # => [:foo, "foo"]
If start is non-negative and outside the array ( >= self.size), extends the array with nil, assigns object at offset start, and ignores length:
a = [:foo, 'bar', 2] a[6, 50] = 'foo' # => "foo" a # => [:foo, "bar", 2, nil, nil, nil, "foo"]
If length is zero, shifts elements at and following offset start and assigns object at offset start:
a = [:foo, 'bar', 2] a[1, 0] = 'foo' # => "foo" a # => [:foo, "foo", "bar", 2]
If length is too large for the existing array, does not extend the array:
a = [:foo, 'bar', 2] a[1, 5] = 'foo' # => "foo" a # => [:foo, "foo"]
When Range argument range is given and object is not an array, removes length - 1 elements beginning at offset start, and assigns object at offset start:
a = [:foo, 'bar', 2] a[0..1] = 'foo' # => "foo" a # => ["foo", 2]
if range.begin is negative, counts backwards from the end of the array:
a = [:foo, 'bar', 2] a[-2..2] = 'foo' # => "foo" a # => [:foo, "foo"]
If the array length is less than range.begin, extends the array with nil, assigns object at offset range.begin, and ignores length:
a = [:foo, 'bar', 2] a[6..50] = 'foo' # => "foo" a # => [:foo, "bar", 2, nil, nil, nil, "foo"]
If range.end is zero, shifts elements at and following offset start and assigns object at offset start:
a = [:foo, 'bar', 2] a[1..0] = 'foo' # => "foo" a # => [:foo, "foo", "bar", 2]
If range.end is negative, assigns object at offset start, retains range.end.abs -1 elements past that, and removes those beyond:
a = [:foo, 'bar', 2] a[1..-1] = 'foo' # => "foo" a # => [:foo, "foo"] a = [:foo, 'bar', 2] a[1..-2] = 'foo' # => "foo" a # => [:foo, "foo", 2] a = [:foo, 'bar', 2] a[1..-3] = 'foo' # => "foo" a # => [:foo, "foo", "bar", 2] a = [:foo, 'bar', 2]
If range.end is too large for the existing array, replaces array elements, but does not extend the array with nil values:
a = [:foo, 'bar', 2] a[1..5] = 'foo' # => "foo" a # => [:foo, "foo"]
Related: see Methods for Assigning.
Returns the element of self specified by the given index or nil if there is no such element; index must be an integer-convertible object.
For non-negative index, returns the element of self at offset index:
a = [:foo, 'bar', 2] a.at(0) # => :foo a.at(2) # => 2 a.at(2.0) # => 2
For negative index, counts backwards from the end of self:
a.at(-2) # => "bar"
Related: Array#[]; see also Methods for Fetching.
Returns the element of self at offset index if index is in range; index must be an integer-convertible object.
With the single argument index and no block, returns the element at offset index:
a = [:foo, 'bar', 2] a.fetch(1) # => "bar" a.fetch(1.1) # => "bar"
If index is negative, counts from the end of the array:
a = [:foo, 'bar', 2] a.fetch(-1) # => 2 a.fetch(-2) # => "bar"
With arguments index and default_value (which may be any object) and no block, returns default_value if index is out-of-range:
a = [:foo, 'bar', 2] a.fetch(1, nil) # => "bar" a.fetch(3, :foo) # => :foo
With argument index and a block, returns the element at offset index if index is in range (and the block is not called); otherwise calls the block with index and returns its return value:
a = [:foo, 'bar', 2] a.fetch(1) {|index| raise 'Cannot happen' } # => "bar" a.fetch(50) {|index| "Value for #{index}" } # => "Value for 50"
Related: see Methods for Fetching.
Adds to self all elements from each array in other_arrays; returns self:
a = [0, 1] a.concat(['two', 'three'], [:four, :five], a) # => [0, 1, "two", "three", :four, :five, 0, 1]
Related: see Methods for Assigning.
Returns a new array that is the union of the elements of self and all given arrays other_arrays; items are compared using eql?:
[0, 1, 2, 3].union([4, 5], [6, 7]) # => [0, 1, 2, 3, 4, 5, 6, 7]
Removes duplicates (preserving the first found):
[0, 1, 1].union([2, 1], [3, 1]) # => [0, 1, 2, 3]
Preserves order (preserving the position of the first found):
[3, 2, 1, 0].union([5, 3], [4, 2]) # => [3, 2, 1, 0, 5, 4]
With no arguments given, returns a copy of self.
Related: see Methods for Combining.
Returns a new array containing only those elements from self that are not found in any of the given other_arrays; items are compared using eql?; order from self is preserved:
[0, 1, 1, 2, 1, 1, 3, 1, 1].difference([1]) # => [0, 2, 3] [0, 1, 2, 3].difference([3, 0], [1, 3]) # => [2] [0, 1, 2].difference([4]) # => [0, 1, 2] [0, 1, 2].difference # => [0, 1, 2]
Returns a copy of self if no arguments are given.
Related: Array#-; see also Methods for Combining.
Returns a new array containing each element in self that is #eql? to at least one element in each of the given other_arrays; duplicates are omitted:
[0, 0, 1, 1, 2, 3].intersection([0, 1, 2], [0, 1, 3]) # => [0, 1]
Each element must correctly implement method #hash.
Order from self is preserved:
[0, 1, 2].intersection([2, 1, 0]) # => [0, 1, 2]
Returns a copy of self if no arguments are given.
Related: see Methods for Combining.
Returns whether other_array has at least one element that is #eql? to some element of self:
[1, 2, 3].intersect?([3, 4, 5]) # => true [1, 2, 3].intersect?([4, 5, 6]) # => false
Each element must correctly implement method #hash.
Related: see Methods for Querying.
Appends object as the last element in self; returns self:
[:foo, 'bar', 2] << :baz # => [:foo, "bar", 2, :baz]
Appends object as a single element, even if it is another array:
[:foo, 'bar', 2] << [3, 4] # => [:foo, "bar", 2, [3, 4]]
Related: see Methods for Assigning.