Swift: components(separatedBy:) vs. split(separator:) - Which One Should You Use?

When working with strings in Swift, breaking them into smaller parts is a common task. You might have come across two different ways to achieve this: components(separatedBy:) and split(separator:). While they seem similar, they behave differently and serve different purposes. Let's dive into their differences and find out when to use each one.

The Basics

components(separatedBy:)

• Returns an array of String ([String]).
• Preserves empty strings when encountering consecutive separators.
• Suitable for splitting text by a specific delimiter.

Example:

let text = "Swift,,is,great"
let result = text.components(separatedBy: ",")
print(result) // ["Swift", "", "is", "great"]

Notice that the empty string between the two commas (",,") is retained in the output.

split(separator:)

• Returns an array of Substring ([Substring]).
• Removes empty substrings by default.
• More performant as it avoids unnecessary string copies.

Example:

let text = "Swift,,is,great"
let result = text.split(separator: ",")
print(result) // ["Swift", "is", "great"]

Here, the empty string between ",," is removed. If you want to retain empty substrings, you can pass an additional parameter:

let resultWithEmpty = text.split(separator: ",", omittingEmptySubsequences: false)
print(resultWithEmpty) // ["Swift", "", "is", "great"]

Key Differences

When to Use Which?

Use components(separatedBy:) when:

• You need an array of String, not Substring.
• You want empty strings to be included in the output.
• You are splitting text based on a fixed delimiter (e.g., parsing CSV data).

Use split(separator:) when:

• You want better performance by working with Substring.
• You don’t need empty strings in the output.
• You want more control over empty sequences using omittingEmptySubsequences.

Final Thoughts

Both components(separatedBy:) and split(separator:) are useful in different scenarios. If you need strict string splitting with empty values retained, go for components(separatedBy:). If performance and efficient memory handling are important, split(separator:) is the way to go.

Next time you’re splitting strings in Swift, pick the right method based on your needs!