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Learn how to format floating point numbers correctly in Swift to ensure a clean, user-friendly output with two decimal places.
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How to Display Floating Point Numbers with Two Decimal Places in Swift

When working with floating point numbers in Swift, you might have encountered an issue where numbers are printed with unnecessarily long decimal places. For instance, you may want your output to show 0.3, 0.4, etc., but instead get something like 0.70000005 or 0.8000001. This behavior can be confusing and can detract from the expected presentation of your data. In this guide, we’ll walk through how to properly format floating point numbers to display just one or two decimal places in Swift.

The Problem

Consider the following example where we are counting down from zero using a floating point number:

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Output:

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In this example, the output shows more decimal places than necessary. This can clutter your output and make it difficult to read. Let's explore how to format these numbers correctly.

Solution: Formatting Numbers in Swift

Using String(format:)

One straightforward way to control the number of decimal places during output is to use the String(format:) initializer. Here’s how you can format a number to display only one decimal place:

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If you need to display two decimal places, you can easily modify the string format:

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Using NumberFormatter

Another powerful method to format numbers in Swift is by using NumberFormatter. This approach provides more flexibility, as it allows you to control various aspects of number formatting. Here’s how to set it up for one decimal place:

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Explanation of the Code:

minimumFractionDigits: This property sets the minimum number of digits after the decimal point.

maximumFractionDigits: This property sets the maximum number of digits after the decimal point.

string(from:): This method converts a Float into an NSNumber, which is required by NumberFormatter.

Conclusion

By applying the methods discussed above, you can ensure that your floating point numbers are displayed with the desired number of decimal places. This not only makes your output cleaner and more professional but also improves the user experience. Whether you choose to use String(format:) or NumberFormatter will depend on your specific needs and preferences.

Now you are ready to format your numbers correctly in Swift! Happy coding!