对嵌入式类型导出字段的访问无法正常进行[重复]

Question

This question already has an answer here:

• My object is not updated even if I use the pointer to a type to update it 3 answers

I am trying to understand embedding in Go and this is what I tried to do -

I created a type A with an exported field X and have a function Update on A update X with user provided input.

type A struct {
    X int
}

func (a A) Update(v int) {
    a.X = v
}

The I define two types A1 and A2 and make them update X with different values. My expectation was that A1's update will not effect A2's update. So I did this -

https://play.golang.org/p/Rjh3hyw_nb0

What I get is all 0's in the output.

Firstly - is the expectation correct? Do A1 and A2 have different reference to A.X

Secondly - why does it print all 0's instead of updated value of X?

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Answer 1

You should define ad pointer of the struct in the pointer receiver as:

func (a *A) Update(v int) { a.X = v }

https://play.golang.org/p/wg7-WvUm7Ra