Ruby/Array/Array Creation
Материал из Wiki.crossplatform.ru
A basic array with []
x = [1, 2, 3, 4] # This array has four elements. # Each element is an integer, and is separated by commas from its neighboring elements. # All the elements are contained within square brackets.
Array.new creates an empty array, represented as [], named months.
# test whether an array is empty or not with the empty? method months = Array.new months.empty? # => true
Arrays don"t need to be set up with predefined entries or have elements allocated manually.
x = [] # The array is empty # Trying to address, say, x[5] results in nothing being returned. puts x[5]
assign an object (such as a string) to each element in the array
month = Array.new(12, "month") # month now appears like this: #["month", "month", "month", "month", "month", "month", "month", "month", "month", # "month", "month", "month"]
Creates a array with the Array class"s new method: array2 = Array.new
array = ["Hello", "there", "AAA", 1, 2, 3] puts array[0] puts array[1] puts array.length array2 = Array.new puts array2.length array2[0] = "Banana" array2[1] = "fish" puts array2[0] + " " + array2[1] puts array2.length
Creating an Array with a Block
# use a block with new, populating each element with what the block evaluates to num = Array.new(10) { |e| e = e * 2 }
Creating Arrays with the new class method:
months = Array.new
Define an array of strings is with the %w notation.
# It assumes that all elements are strings (even nil) months = %w[ nil January February March April May June July August September October November December ] # This produces the array months: # ["nil", "January", "February", "March", "April", "May", "June", "July", "August", # "September", "October", "November", "December"]
Examples of the methods provided by Enumerable
puts [1,2,3,4].collect { |i| i.to_s + "x" } puts [1,2,3,4].detect { |i| i.between?(2,3) } puts [1,2,3,4].select { |i| i.between?(2,3) } puts [4,1,3,2].sort puts [1,2,3,4].max puts [1,2,3,4].min
if you submit a set of strings, Array accepts them as a single, concatenated element.
d = Array( "H" "D" "L" ) p d
return the size of an array with either the size or length method
months = Array.new(12) months.size # => 12 # or: months.length # => 12
set the size of an array (the number of elements in an array)
months = Array.new(12) # or like this: months = Array.new 12
store text strings as well as numbers in arrays
array = ["Hello", "there", "AAA", 1, 2, 3] puts array[1] #prints "there" puts array[4] #prints 2
takes a range as an argument to create an array of digits.
digits = Array(0..9) # => [1, 2, 3, 4, 5, 6, 7, 8, 9]
To create an array, you use the [] operator
array = [1, 2, 3] # This creates an array with three elements, 1, 2, and 3. # You access those elements using an array index like this: puts array[0] #prints 1 puts array[1] #prints 2 puts array[2] #prints 3
