Why Should You Avoid Using %v for Printing Integers and Strings in Go?

The Drawbacks of Using %v for Printing Integers and Strings

While it's permissible to use %v for both integers and strings, it's not recommended as it can lead to unexpected behavior with the "fmt" package.

Understanding the Role of %d and %v

• %d specifically prints integers using base 10.
• %v attempts to print values using their default formatting, which can be overridden depending on the implemented interfaces.

Example with Custom Formatter

Output:

In this example, although we use %v, the String() method of MyInt is invoked as it implements the String() method from the fmt.Stringer interface, resulting in the custom formatting applied to the integer.

Default Formatting Rules for %v

According to the "fmt" package documentation, %v attempts to use the following rules in order:

• Invokes the Formatter interface if implemented by the operand.
• Invokes the GoStringer interface if #%v format is used.
• Uses the Error method if the operand implements the error interface.
• Uses the String() method if available.

Potential Issues

Printing integers with %v can potentially lead to confusion when the default formatting overrides the expected %d behavior. For example, when dealing with special types like pointers or complex values, using %v might result in unexpected output.

Conclusion

While %v offers flexibility in formatting, it's generally advisable to use specific verbs like %d for integers and %s for strings to ensure clarity and avoid potential ambiguity.

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