Ruby/Array/Array Index
Материал из Wiki.crossplatform.ru
Assign string value to an integer array
x = [1, 2, 3, 4] x[2] = "Fish" * 3 puts x[2]
Elements can be accessed by their index (their position within the array).
x = [1, 2, 3, 4] puts x[2]
get the flip side with index.
# It returns the index of the first element that matches the object: q1 = %w[ January February March ] q1.index "March" # => 2
Mix up an array
array = [1,2,3,4,5] new_array = [] front_index = 0 back_index = array.length-1 while front_index <= back_index new_array << array[front_index] front_index += 1 if front_index <= back_index new_array << array[back_index] back_index -= 1 end end p new_array # => [1, 5, 2, 4, 3]
The first element in the array corresponds to array index 0, not 1,
# and the second element is at index 1, the third at index 2, and so on. array = [1, 2, 3] array[0] = 4 #assigns 4 to array[0] array[1] = 5 #assigns 5 to array[1] array[2] = 6 #assigns 6 to array[2] puts array[2] #prints 6
The last element in the array is -1, the previous one -2, the previous one -3
array = ["Hello", "there", "AAA", 1, 2, 3] puts array[-1] #prints 3 puts array[-2] #prints 2 puts array[-3] #prints 1
To change an element, you can simply assign it a new value or manipulate it
x = [1, 2, 3, 4] x[2] += 1 puts x[2]
Use a variable (or a constant) as an array index
array = ["Hello", "there", "AAA", 1, 2, 3] index_value = 0 puts array[index_value] #prints "Hello" index_value = 1 puts array[index_value] #prints "there" index_value = 2 puts array[index_value] #prints "AAA"
Use negative array indices in Ruby.
# Negative indices count from the end of the array back to the beginning of the array. array = ["Hello", "there", "AAA", 1, 2, 3] puts array[-1] #prints 3
Use until and array element to loop through an array
array = ["cherry", "strawberry", "orange"] index = 0 until index == array.length puts "At position #{index}: #{array[index]}" index += 1 end
Use while and array index to get element from an array
array = ["cherry", "strawberry", "orange"] index = 0 while index < array.length puts "At position #{index}: #{array[index]}" index += 1 end
