How is array.collect! different from array.collect in Ruby?
array.collect! and array.collect both do the same thing. They are both methods used to invoke the block argument given to them on each element of an array. After the operation, a new array is returned by the block.
However, the difference is that array.collect! permanently changes the original array, but array.collect does not.
Syntax
array.collect{|item|block}
# OR
array.collect!{|item|block}
Parameter
item: This represents each element in the array.
block: What should happen to each item is specified here.
Return value
A new array is returned that contains values returned by the block.
Example
In the example below, we will demonstrate the difference between the methods array.collect and array.collect!.
# create arraysarray1 = [1, 2, 3, 4, 5]array2 = [1, 2, 3, 4, 5]# call array.collect on array1# call array.collect! on array2# array1 : add two to each elementarr1 = array1.collect{|item| item + 2}arr2 = array2.collect!{|item| item + 2}# print returned values to consoleputs "arr1: #{arr1}"puts "arr2: #{arr2}"# now print the original arraysputs "array1: #{array1}"puts "array2: #{array2}"
Explanation
In the code above:
-
We call
array.collectonarray1and callarray.collect!onarray2. They are both meant to increment each element of the array by two. -
The returned arrays for
array1andarray2are stored inarr1andarr2respectively. -
After this, in lines 12 and 13, we print the returned arrays to the console. The result shows that elements of the two arrays were incremented by 2.
-
The magic happens when we now print the original arrays to the console. We observe that
array1did not change, butarray2did. This is becausearray.collect!permanently modifies the array that calls it butarray.collectdoes not.
