附加到作为地图中值的切片[重复]

Question

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• Go: append directly to slice found in a map 1 answer

I want to append to a slice that is a value of a map, e.g. given m map[string][]string:

if values, exists := m[key]; exists {
    values = append(values, v)
//  I don't want to call: m[key] = values
} else {
    m[key] = []string{ v }
}

That obviously doesn't work, so I tried instead of appending the value as is, to do something like:

valuesPtr := &values
*values = append(values, v)

But that doesn't work either. How can I do that?

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Answer 1

You cannot do that.

append returns a new slice, since a slice may have to be resized to complete the append. You must update your map to use the newly returned slice, which cannot be done without referencing by key.