golang和指针接收器中的自定义错误

Question

Reading about value receivers vs pointer receivers across the web and stackoverflow, I understand the basic rule to be: If you don't plan to modify the receiver, and the receiver is relatively small, there is no need for pointers.

Then, reading about implementing the error interface (eg. https://blog.golang.org/error-handling-and-go), I see that examples of the Error() function all use pointer receiver.

Yet, we are not modifying the receiver, and the struct is very small.

I feel like the code is much nicer without pointers (return &appError{} vs return appError{}).

Is there a reason why the examples are using pointers?

Answer 1

No :)

https://blog.golang.org/error-handling-and-go#TOC_2.

Go interfaces allow for anything that complies with the error interface to be handled by code expecting error

type error interface {
    Error() string
}

Like you mentioned, If you don't plan to modify state there is little incentive to pass around pointers:

• allocating to heap
• GC pressure
• Mutable state and concurrency, etc

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On a random rant , Anecdotally, I personally think that seeing examples like this one are why new go programers favor pointer receivers by default.