在Go中，是否可以在不需要星号取消引用的情况下将变量分配给someArray [someIndex]？

Question

This works:

pressure := &dataDump[845]
CurrentPressure := *pressure

But is there a way to change the first line so that pressure is an alias for dataDump[845] and so no asterisk is needed:

CurrentPressure := pressure

Answer 1

For "changing" data

By "changing" data I mean if the dataDump array / slice changes, you want your pressure to reflect the changes.

This is not possible in Go. What you want would require to explicitly specify the memory address where a variable is to be created / placed.

Your best option is to use a pointer which you included in your question.

Another alternative would be to create a function, e.g.:

function pressure() int {
    return dataDump[845]
}

And using it:

currentPressure := pressure()

For "static" data

If dataDump doesn't change once it's acquired, then this is not a problem. You can use a simple non-pointer variable like this:

pressure := dataDump[845] // Not a pointer to the element but a copy of it

And then:

currentPressure := pressure

But then in this case currentPressure isn't even needed, you can just use pressure (or maybe name it currentPressure in the first place).

Using memory layout

I don't know how you acquire your data, but in some cases it is possible to provide the Go value where you want the data to be placed / unmarshaled. Such cases may be reading the data from a file, or from a TCP connection.

If this is you case, you may use a struct carefully planning the memory layout of the data you get, and then you may use struct fields which you can declare to be non-pointers.

Example:

type dataDump struct {
    _ [845]int32 // Some unused data

    pressure int32
}

If you can "unmarshal" your data into a value of this struct, then you can obtain the current pressure like this:

dump := dataDump{}
// Unmarshal into dump
currentPressure := dump.pressure

If you go down this way, be aware of the Spec: Size and alignment guarantees. Care must be taken due to implicit alignments!

See related questions for more details about laying out memory:

Why use arrays instead of slices?

Why have arrays in Go?