Go Interfaces: Nil Interface vs. Nil Value – How to Tell the Difference?

How to Check for Nil and Nil Interface in Go

When working with interfaces in Go, it's necessary to differentiate between a nil interface and an interface containing a nil value. The code snippet presented in the question employs a helper function to perform this check, but the use of reflection and deferred recovery introduces potential complexities.

The provided solution from Kyle in the golang-nuts mailing list offers a more straightforward approach. It suggests that in the absence of storing (*T)(nil) in an interface, a simple comparison against nil is sufficient to ascertain whether the interface is nil. Conversely, assigning untyped nil to an interface is always permitted.

This approach eliminates the need for reflection and error handling, making the check more efficient and less susceptible to exceptions. It's important to remember that (*T)(nil) should never be stored in an interface, as this can lead to unexpected behavior and compromise the reliability of the comparison.

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