I created an array this way:
arr = Array.new(4, Array.new(4, '*'))
When I try to change one element, for example the first element of the first array:
arr[0][0] = 3
then every first element is changed.
print arr
[[3, "*", "*", "*"], [3, "*", "*", "*"], [3, "*", "*", "*"], [3, "*", "*", "*"]]
Can someone explain why this is happening?
Do:
arr = Array.new(4) { Array.new(4, '*') }
Ruby array is in fact a set of pointers, which points onto some other objects n the memory. In your code all the pointers point to the same object created with Array.new(4, '*'). if, instead of the value, you will pass a block, this block will be executed for every element of the array, so each pointer will point to a new object in the memory.
In fact, the code above still have a similar issue with a string '*'. You should use same method to fix it:
arr = Array.new(4) { Array.new(4) { '*' } }
