Playgrounds is a powerful tool for trying out code and getting the result. As its name suggests, it's a place to play. In a playground, Swift code is evaluated immediately, which is the same as in REPL. You can create a new playground by going to File | New | Playground. Enter the file name and create it.
A playground consists of two parts, which are shown in the next screenshot:
Editor
Result
Almost all the code examples shown in this book were created in playgrounds. As an example, let's create an array and play with it. We can apply filter and map functions and print the count of objects in an array:
You will see the result of the evaluated code appearing as you type. If you move the cursor to the one of the lines in the result section, it will become highlighted and two buttons will appear:
Quick Look
Show / Hide result
Quick Look will display more details about the executed operation. This functionality is particularly interesting for functions. As an example, if you click...