What Is a Labeled Statement in Swift?

How to break from an outer loop inside a nested loop

Today, we will learn about a lesser-known feature in Swift: labeled statements.

Labeled statements allow us to control the flow of our program execution. The concept is similar to goto in other programming languages. For example, we may use it to break from the outer loop inside a nested one, which is exactly what we are going to do now.

Let’s Start

Say we have the following Dictionary of type [Int: [String]]:

And we want to loop iterate through it, breaking the loop once we find Jan in the process.

Let’s append the following:

We can see that we first sort the periods property by year in ascending order. Then we access each individual month and check if it is equal to Jan. Once we find Jan, we call break outerLoop and the execution of the outerLoop stops:

Now the full source code looks like this:

Wrapping Up

Note that this feature should not be used too much and only in certain circumstances when you feel you have no other option.

Interested in other Swift features? Feel free to check out my other relevant pieces:

• What Is OptionSet and When You Should Use It?
• What Is the CustomStringConvertible Protocol in Swift?
• What Is the vDSP Framework in Swift?
• What Is the Equatable Protocol in Swift?
• When to Use the Comparable Protocol in Swift

Thanks for reading!