Appends object to self; returns self:
a = [:foo, 'bar', 2] a << :baz # => [:foo, "bar", 2, :baz]
Appends object as one element, even if it is another Array:
a = [:foo, 'bar', 2] a1 = a << [3, 4] a1 # => [:foo, "bar", 2, [3, 4]]
Appends trailing elements.
Appends each argument in objects to self; returns self:
a = [:foo, 'bar', 2] a.push(:baz, :bat) # => [:foo, "bar", 2, :baz, :bat]
Appends each argument as one element, even if it is another Array:
a = [:foo, 'bar', 2] a1 = a.push([:baz, :bat], [:bam, :bad]) a1 # => [:foo, "bar", 2, [:baz, :bat], [:bam, :bad]]
Array#append is an alias for Array#push.
Removes and returns trailing elements.
When no argument is given and self is not empty, removes and returns the last element:
a = [:foo, 'bar', 2] a.pop # => 2 a # => [:foo, "bar"]
Returns nil if the array is empty.
When a non-negative Integer argument n is given and is in range, removes and returns the last n elements in a new Array:
a = [:foo, 'bar', 2] a.pop(2) # => ["bar", 2]
If n is positive and out of range, removes and returns all elements:
a = [:foo, 'bar', 2] a.pop(50) # => [:foo, "bar", 2]
Removes and returns leading elements.
When no argument is given, removes and returns the first element:
a = [:foo, 'bar', 2] a.shift # => :foo a # => ['bar', 2]
Returns nil if self is empty.
When positive Integer argument n is given, removes the first n elements; returns those elements in a new Array:
a = [:foo, 'bar', 2] a.shift(2) # => [:foo, 'bar'] a # => [2]
If n is as large as or larger than self.length, removes all elements; returns those elements in a new Array:
a = [:foo, 'bar', 2] a.shift(3) # => [:foo, 'bar', 2]
If n is zero, returns a new empty Array; self is unmodified.
Prepends the given objects to self:
a = [:foo, 'bar', 2] a.unshift(:bam, :bat) # => [:bam, :bat, :foo, "bar", 2]
Array#prepend is an alias for Array#unshift.
Inserts given objects before or after the element at Integer index offset; returns self.
When index is non-negative, inserts all given objects before the element at offset index:
a = [:foo, 'bar', 2] a.insert(1, :bat, :bam) # => [:foo, :bat, :bam, "bar", 2]
Extends the array if index is beyond the array (index >= self.size):
a = [:foo, 'bar', 2] a.insert(5, :bat, :bam) a # => [:foo, "bar", 2, nil, nil, :bat, :bam]
Does nothing if no objects given:
a = [:foo, 'bar', 2] a.insert(1) a.insert(50) a.insert(-50) a # => [:foo, "bar", 2]
When index is negative, inserts all given objects after the element at offset index+self.size:
a = [:foo, 'bar', 2] a.insert(-2, :bat, :bam) a # => [:foo, "bar", :bat, :bam, 2]
Iterates over array elements.
When a block given, passes each successive array element to the block; returns self:
a = [:foo, 'bar', 2] a.each {|element| puts "#{element.class} #{element}" }
Output:
Symbol foo String bar Integer 2
Allows the array to be modified during iteration:
a = [:foo, 'bar', 2] a.each {|element| puts element; a.clear if element.to_s.start_with?('b') }
Output:
foo bar
When no block given, returns a new Enumerator:
a = [:foo, 'bar', 2] e = a.each e # => #<Enumerator: [:foo, "bar", 2]:each> a1 = e.each {|element| puts "#{element.class} #{element}" }
Output:
Symbol foo String bar Integer 2
Related: each_index, reverse_each.
Returns the count of elements in self.
Returns the count of elements in self.
Returns true if the count of elements in self is zero, false otherwise.
Returns the index of a specified element.
When argument object is given but no block, returns the index of the first element element for which object == element:
a = [:foo, 'bar', 2, 'bar'] a.index('bar') # => 1
Returns nil if no such element found.
When both argument object and a block are given, calls the block with each successive element; returns the index of the first element for which the block returns a truthy value:
a = [:foo, 'bar', 2, 'bar'] a.index {|element| element == 'bar' } # => 1
Returns nil if the block never returns a truthy value.
When neither an argument nor a block is given, returns a new Enumerator:
a = [:foo, 'bar', 2] e = a.index e # => #<Enumerator: [:foo, "bar", 2]:index> e.each {|element| element == 'bar' } # => 1
Array#find_index is an alias for Array#index.
Related: rindex.
Returns the index of the last element for which object == element.
When argument object is given but no block, returns the index of the last such element found:
a = [:foo, 'bar', 2, 'bar'] a.rindex('bar') # => 3
Returns nil if no such object found.
When a block is given but no argument, calls the block with each successive element; returns the index of the last element for which the block returns a truthy value:
a = [:foo, 'bar', 2, 'bar'] a.rindex {|element| element == 'bar' } # => 3
Returns nil if the block never returns a truthy value.
When neither an argument nor a block is given, returns a new Enumerator:
a = [:foo, 'bar', 2, 'bar'] e = a.rindex e # => #<Enumerator: [:foo, "bar", 2, "bar"]:rindex> e.each {|element| element == 'bar' } # => 3
Related: index.
Returns the new String formed by joining the array elements after conversion. For each element element
Uses element.to_s if element is not a kind_of?(Array).
Uses recursive element.join(separator) if element is a kind_of?(Array).
With no argument, joins using the output field separator, $,:
a = [:foo, 'bar', 2] $, # => nil a.join # => "foobar2"
With string argument separator, joins using that separator:
a = [:foo, 'bar', 2] a.join("\n") # => "foo\nbar\n2"
Joins recursively for nested Arrays:
a = [:foo, [:bar, [:baz, :bat]]] a.join # => "foobarbazbat"
Returns a new Array with the elements of self in reverse order.
a = ['foo', 'bar', 'two'] a1 = a.reverse a1 # => ["two", "bar", "foo"]
Reverses self in place:
a = ['foo', 'bar', 'two'] a.reverse! # => ["two", "bar", "foo"]
Returns a new Array formed from self with elements rotated from one end to the other.
When no argument given, returns a new Array that is like self, except that the first element has been rotated to the last position:
a = [:foo, 'bar', 2, 'bar'] a1 = a.rotate a1 # => ["bar", 2, "bar", :foo]
When given a non-negative Integer count, returns a new Array with count elements rotated from the beginning to the end:
a = [:foo, 'bar', 2] a1 = a.rotate(2) a1 # => [2, :foo, "bar"]
If count is large, uses count % array.size as the count:
a = [:foo, 'bar', 2] a1 = a.rotate(20) a1 # => [2, :foo, "bar"]
If count is zero, returns a copy of self, unmodified:
a = [:foo, 'bar', 2] a1 = a.rotate(0) a1 # => [:foo, "bar", 2]
When given a negative Integer count, rotates in the opposite direction, from end to beginning:
a = [:foo, 'bar', 2] a1 = a.rotate(-2) a1 # => ["bar", 2, :foo]
If count is small (far from zero), uses count % array.size as the count:
a = [:foo, 'bar', 2] a1 = a.rotate(-5) a1 # => ["bar", 2, :foo]
Rotates self in place by moving elements from one end to the other; returns self.
When no argument given, rotates the first element to the last position:
a = [:foo, 'bar', 2, 'bar'] a.rotate! # => ["bar", 2, "bar", :foo]
When given a non-negative Integer count, rotates count elements from the beginning to the end:
a = [:foo, 'bar', 2] a.rotate!(2) a # => [2, :foo, "bar"]
If count is large, uses count % array.size as the count:
a = [:foo, 'bar', 2] a.rotate!(20) a # => [2, :foo, "bar"]
If count is zero, returns self unmodified:
a = [:foo, 'bar', 2] a.rotate!(0) a # => [:foo, "bar", 2]
When given a negative Integer count, rotates in the opposite direction, from end to beginning:
a = [:foo, 'bar', 2] a.rotate!(-2) a # => ["bar", 2, :foo]
If count is small (far from zero), uses count % array.size as the count:
a = [:foo, 'bar', 2] a.rotate!(-5) a # => ["bar", 2, :foo]
Returns a new Array whose elements are those from self, sorted.
With no block, compares elements using operator <=> (see Comparable):
a = 'abcde'.split('').shuffle a # => ["e", "b", "d", "a", "c"] a1 = a.sort a1 # => ["a", "b", "c", "d", "e"]
With a block, calls the block with each element pair; for each element pair a and b, the block should return an integer:
Negative when b is to follow a.
Zero when a and b are equivalent.
Positive when a is to follow b.
Example:
a = 'abcde'.split('').shuffle a # => ["e", "b", "d", "a", "c"] a1 = a.sort {|a, b| a <=> b } a1 # => ["a", "b", "c", "d", "e"] a2 = a.sort {|a, b| b <=> a } a2 # => ["e", "d", "c", "b", "a"]
When the block returns zero, the order for a and b is indeterminate, and may be unstable:
a = 'abcde'.split('').shuffle a # => ["e", "b", "d", "a", "c"] a1 = a.sort {|a, b| 0 } a1 # => ["c", "e", "b", "d", "a"]
Related: Enumerable#sort_by.
Returns self with its elements sorted in place.
With no block, compares elements using operator <=> (see Comparable):
a = 'abcde'.split('').shuffle a # => ["e", "b", "d", "a", "c"] a.sort! a # => ["a", "b", "c", "d", "e"]
With a block, calls the block with each element pair; for each element pair a and b, the block should return an integer:
Negative when b is to follow a.
Zero when a and b are equivalent.
Positive when a is to follow b.
Example:
a = 'abcde'.split('').shuffle a # => ["e", "b", "d", "a", "c"] a.sort! {|a, b| a <=> b } a # => ["a", "b", "c", "d", "e"] a.sort! {|a, b| b <=> a } a # => ["e", "d", "c", "b", "a"]
When the block returns zero, the order for a and b is indeterminate, and may be unstable:
a = 'abcde'.split('').shuffle a # => ["e", "b", "d", "a", "c"] a.sort! {|a, b| 0 } a # => ["d", "e", "c", "a", "b"]
Calls the block, if given, with each element of self; returns a new Array whose elements are the return values from the block:
a = [:foo, 'bar', 2] a1 = a.map {|element| element.class } a1 # => [Symbol, String, Integer]
Returns a new Enumerator if no block given:
a = [:foo, 'bar', 2] a1 = a.map a1 # => #<Enumerator: [:foo, "bar", 2]:map>
Array#collect is an alias for Array#map.
Calls the block, if given, with each element; replaces the element with the block’s return value:
a = [:foo, 'bar', 2] a.map! { |element| element.class } # => [Symbol, String, Integer]
Returns a new Enumerator if no block given:
a = [:foo, 'bar', 2] a1 = a.map! a1 # => #<Enumerator: [:foo, "bar", 2]:map!>
Array#collect! is an alias for Array#map!.
Calls the block, if given, with each element of self; returns a new Array whose elements are the return values from the block:
a = [:foo, 'bar', 2] a1 = a.map {|element| element.class } a1 # => [Symbol, String, Integer]
Returns a new Enumerator if no block given:
a = [:foo, 'bar', 2] a1 = a.map a1 # => #<Enumerator: [:foo, "bar", 2]:map>
Array#collect is an alias for Array#map.
Calls the block, if given, with each element; replaces the element with the block’s return value:
a = [:foo, 'bar', 2] a.map! { |element| element.class } # => [Symbol, String, Integer]
Returns a new Enumerator if no block given:
a = [:foo, 'bar', 2] a1 = a.map! a1 # => #<Enumerator: [:foo, "bar", 2]:map!>
Array#collect! is an alias for Array#map!.
Calls the block, if given, with each element of self; returns a new Array containing those elements of self for which the block returns a truthy value:
a = [:foo, 'bar', 2, :bam] a1 = a.select {|element| element.to_s.start_with?('b') } a1 # => ["bar", :bam]
Returns a new Enumerator if no block given:
a = [:foo, 'bar', 2, :bam] a.select # => #<Enumerator: [:foo, "bar", 2, :bam]:select>
Array#filter is an alias for Array#select.
Calls the block, if given with each element of self; removes from self those elements for which the block returns false or nil.
Returns self if any elements were removed:
a = [:foo, 'bar', 2, :bam] a.select! {|element| element.to_s.start_with?('b') } # => ["bar", :bam]
Returns nil if no elements were removed.
Returns a new Enumerator if no block given:
a = [:foo, 'bar', 2, :bam] a.select! # => #<Enumerator: [:foo, "bar", 2, :bam]:select!>
Array#filter! is an alias for Array#select!.