- Create, read, update, and delete elements from arrays
In this lab, we will be coding the solutions for each of the above tasks in the
body of a method. In lib/array_crud.rb
we've defined a series of methods for
you, each of which is responsible for one of the tasks above. Your job is to
write the code in the body of each method to get the test passing.
Let's go through the first challenge together.
Let's run our test suite to get started. Run the tests one at a time with the
learn test --fail-fast
command in your terminal.
If we do so, we'll see our first failure:
Our test is telling us that we are expected to code the content of our
#create_an_empty_array
method such that a new, empty array is created and
returned. Our test expected
an empty array, []
, but got nil
.
Open up lib/array_crud.rb
and check out the #create_an_empty_array
method.
It's empty! Let's write the code that will get the test passing.
We'll use the literal constructor to make a new array with nothing in it:
def create_an_empty_array
[]
end
Run the test suite again and we should be passing that first test.
This method should use the literal constructor to create a new array, just like we did above. This time, however, create an array that contains four elements. The four elements can be any elements of your choosing, as long as there are only four of them.
This method takes in two arguments, an array and the element we want to add to
it. Use the <<
(shovel) method or the #push
method to add that element to
the end of the new array.
This method takes in two arguments, an array and the element we want to add to
it. Use the #unshift
method to add that element to the start of that array.
This method takes in one argument, the array on which we want to operate. Use
the #pop
method to remove the last item from the array.
This method takes in one argument, the array on which we want to operate. Use
the #shift
method to remove the first item from the array.
This method takes in two arguments, an array and the index number whose element
we want to retrieve. Use the []
, bracket method, to return the element stored
at that index number of the given array.
This method takes in one argument, the array from which we want to retrieve an
element. Use []
notation to return the value stored at the first index of the
array. Remember that arrays are zero-indexed. This means that the first index
number is 0
and it counts up from there. So, the first element of an array is
stored at index 0
.
This method takes in one argument, the array from which we want to retrieve an
element. There are a number of ways to do this, but we recommend using the []
method with the following hint:
The last element of an array is considered to be stored at an index of -1
.