Using the join method

We've walked through the split method, which allows you to convert a string into a collection of characters. Thankfully, Ruby also has a method that does the opposite, which is to allow you to convert an array of characters into a single string, and that method is called join. Let's imagine a situation where we're asked to reverse the words in a string. This is a common Ruby coding interview question, so it's an important concept to understand, since it tests your knowledge of how string works in Ruby. Let's imagine that we have a string, such as this:

str = "backwards am I" 

If we're asked to reverse the words in the string, the pseudocode for the algorithm would be as follows:

1. Split the string into words.
2. Reverse the order of the words.
3. Merge all of the split words back into a single string.

We can actually accomplish each of these requirements in a single line of Ruby code. The following code snippet will perform the task:

str.split.reverse.join(' ') 

This code will convert the single string into an array of strings, for the example, it will equal ["backwards", "am", "I"]. From there, it will reverse the order of the array elements, so the array will equal ["I", "am", "backwards"]. With the words reversed, now we simply need to merge the words into a single string, which is where the join method comes in. Running the join method will convert all of the words in the array into one string.