dongtong848825 2016-03-27 07:47
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`(* RawMessage)(nil)`是什么意思?

The section Interface checks from Effective Go recommends

var _ json.Marshaler = (*RawMessage)(nil)

as a compile-time check that RawMessage implements Marshaler.

I get how the assignment does the type check but what does the right side actually mean?

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  • dongzhi2014 2016-03-27 07:47
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    Ok, I figured it out. It creates a new *RawMessage (pointer to RawMessage) that is nil by casting nil to *RawMessage. I would have expected

    *RawMessage(nil)
    

    but that doesn't work because the cast conversion seems to take precedence over the pointer operator, so it would become a dereference.

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